CN116219242B - A high-strength, high-toughness, high-thermal-conductivity magnesium alloy and a processing method thereof - Google Patents
A high-strength, high-toughness, high-thermal-conductivity magnesium alloy and a processing method thereof Download PDFInfo
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- 229910000861 Mg alloy Inorganic materials 0.000 title claims abstract description 239
- 238000003672 processing method Methods 0.000 title abstract description 6
- 239000007787 solid Substances 0.000 claims abstract description 98
- 239000000956 alloy Substances 0.000 claims abstract description 86
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 83
- 239000011777 magnesium Substances 0.000 claims abstract description 66
- 238000000034 method Methods 0.000 claims abstract description 35
- 230000009974 thixotropic effect Effects 0.000 claims abstract description 32
- 238000001746 injection moulding Methods 0.000 claims abstract description 31
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 24
- 238000012545 processing Methods 0.000 claims abstract description 10
- 229910052718 tin Inorganic materials 0.000 claims abstract description 6
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 5
- -1 wherein La≤2.0% Inorganic materials 0.000 claims abstract 2
- 238000010438 heat treatment Methods 0.000 claims description 49
- 239000002002 slurry Substances 0.000 claims description 46
- 238000010008 shearing Methods 0.000 claims description 38
- 230000032683 aging Effects 0.000 claims description 33
- 239000002245 particle Substances 0.000 claims description 33
- 239000000243 solution Substances 0.000 claims description 29
- 230000004907 flux Effects 0.000 claims description 23
- 238000002347 injection Methods 0.000 claims description 16
- 239000007924 injection Substances 0.000 claims description 16
- 230000008018 melting Effects 0.000 claims description 16
- 238000002844 melting Methods 0.000 claims description 16
- 239000002994 raw material Substances 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 15
- 239000004615 ingredient Substances 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 229910019064 Mg-Si Inorganic materials 0.000 claims description 6
- 229910019406 Mg—Si Inorganic materials 0.000 claims description 6
- 239000007790 solid phase Substances 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims 4
- 230000001681 protective effect Effects 0.000 claims 2
- 229910052746 lanthanum Inorganic materials 0.000 abstract description 14
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 11
- 229910052684 Cerium Inorganic materials 0.000 abstract description 10
- 238000005516 engineering process Methods 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 238000004321 preservation Methods 0.000 description 26
- 239000012071 phase Substances 0.000 description 24
- 239000000463 material Substances 0.000 description 21
- 238000005728 strengthening Methods 0.000 description 19
- 238000007670 refining Methods 0.000 description 16
- 238000003723 Smelting Methods 0.000 description 12
- 238000005266 casting Methods 0.000 description 11
- 238000004512 die casting Methods 0.000 description 11
- 229910052725 zinc Inorganic materials 0.000 description 10
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 9
- 229910052749 magnesium Inorganic materials 0.000 description 9
- 230000017525 heat dissipation Effects 0.000 description 7
- 238000005275 alloying Methods 0.000 description 6
- 238000011049 filling Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- 229910001297 Zn alloy Inorganic materials 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 150000002910 rare earth metals Chemical class 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910009378 Zn Ca Inorganic materials 0.000 description 2
- 229910003120 Zn-Ce Inorganic materials 0.000 description 2
- 229910007612 Zn—La Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 1
- 229910018137 Al-Zn Inorganic materials 0.000 description 1
- 229910018573 Al—Zn Inorganic materials 0.000 description 1
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 1
- 229910003023 Mg-Al Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/007—Semi-solid pressure die casting
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
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- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Forging (AREA)
- Powder Metallurgy (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
一种高强韧高导热镁合金及其加工方法，其成分重量百分比为：Zn：8.0～12.0％，Ca或Mn中的一种或两种，Ca≤2.0％，Mn≤2.0％，还包括La、Ce、Si、Sb、Zr、Sn中的一种或多种，其中，La≤2.0％，Ce≤2.0％，Si≤2.5％，Sb≤2.0％，Zr≤1.0％，Sn≤2.0％，其余为Mg以及不可避免的杂质。本发明高强韧高导热镁合金在不添加价格高昂的稀土元素的前提下，采用低成本的合金配方，解决现有镁合金无法同时兼顾高导热性和高强度的问题；该镁合金导热系数≥115W/(m·K)、屈服强度≥200MPa、伸长率≥8％。本发明采用半固态触变注射成型技术进行加工，其工艺难度小，成本低廉，便于规模化量产，同时可制造出变形工艺无法制造的结构复杂镁合金产品。A high-strength, toughness and high-thermal conductivity magnesium alloy and a processing method thereof, wherein the weight percentage of the components is: Zn: 8.0-12.0%, one or two of Ca or Mn, Ca≤2.0%, Mn≤2.0%, and also includes one or more of La, Ce, Si, Sb, Zr, Sn, wherein La≤2.0%, Ce≤2.0%, Si≤2.5%, Sb≤2.0%, Zr≤1.0%, Sn≤2.0%, and the rest is Mg and inevitable impurities. The high-strength, toughness and high-thermal conductivity magnesium alloy of the present invention adopts a low-cost alloy formula without adding expensive rare earth elements, thereby solving the problem that the existing magnesium alloy cannot take into account both high thermal conductivity and high strength at the same time; the thermal conductivity of the magnesium alloy is ≥115W/(m·K), the yield strength is ≥200MPa, and the elongation is ≥8%. The present invention adopts semi-solid thixotropic injection molding technology for processing, which has low process difficulty, low cost, is convenient for large-scale mass production, and can manufacture magnesium alloy products with complex structures that cannot be manufactured by deformation process.
Description
Technical Field
The invention relates to the technical field of magnesium alloy material forming, in particular to a high-strength and high-heat-conductivity magnesium alloy and a processing method thereof.
Background
Magnesium is the lightest engineering construction material at present, with a density of 1.738g/cm 3, about 2/3 of aluminum, 1/4 of steel. Besides the characteristics of structural materials, magnesium and magnesium alloy also have the characteristics of functional materials, such as high electromagnetic shielding performance, good damping performance and excellent heat conduction performance, so that the magnesium and magnesium alloy is also considered as a lightweight material with the most development prospect in the fields of aerospace, rail transit, automobile parts, 3C products and the like.
The heat conductivity of pure magnesium at room temperature is high, about 154.5W/(m.K), and the heat conductivity per unit mass is slightly better than that of aluminum. However, the yield strength of pure magnesium cast at room temperature is only 21MPa, and it cannot be used as a structural member. Alloying is an effective way to improve the mechanical properties of magnesium alloys, but the addition of alloying elements significantly reduces the heat conductivity of magnesium alloys. For example, the common die-casting magnesium alloys Mg-9Al-1Zn (AZ 91) and Mg-6Al-0.5Mn (AM 60) have thermal conductivities which are all smaller than 70W/(m.K) and far lower than that of pure magnesium.
At present, the heat dissipation/heat conduction parts of the magnesium alloy are basically made of the commercial magnesium alloy with low heat conductivity, so that the requirements of high heat conduction products cannot be met. The thermal conductivity coefficient of commercial brand as-cast ZK61 magnesium alloy can reach 115W/(m.K), but the yield strength is usually lower than 180MPa, and the requirements of high strength and toughness and high thermal conductivity of the structural material of the heat dissipation system in the fields of aerospace devices and vehicles are hardly met. The cast rare earth magnesium alloy has higher heat conduction performance (the heat conductivity is more than or equal to 115W/(m.K)) and mechanical performance (the yield strength is more than or equal to 180 MPa), but the cost of the rare earth magnesium alloy is higher, and the density of the magnesium alloy can be obviously improved by adding a large amount of rare earth elements.
The magnesium alloy with high mechanical property and high heat-conducting property can be prepared by deformation processes such as rolling, forging, extrusion and the like reported in the literature, but the close-packed hexagonal crystal structure of the magnesium alloy leads to complex deformation processes and high cost, and particularly when facing magnesium alloy products with complex structures, the deformation processes often cannot meet the requirements.
Semi-solid thixotropic injection molding utilizes the special flowable characteristics of metal in semi-solid state to perform injection molding. The semi-solid state phenomenon of metal, namely, the metal in a solid-liquid two-phase temperature zone can be stirred by only quite low shearing stress, at the moment, the shearing force is about three orders of magnitude lower than that of the same liquid metal, the metal is easy to form, and the metal is better than the mechanical property of a traditional dendrite solidification casting, so that the metal is particularly suitable for magnesium alloy forming.
Chinese patent CN109136699B discloses a high heat conduction magnesium alloy, an inverter shell, an inverter and an automobile, and the magnesium alloy is prepared by the following chemical components, by mass, 2.0-4.0% of Al, 0.1-0.3% of Mn, 1.0-2.0% of La, 2.0-4.0% of Ce, 0.1-1% of Nd, 0.5-2% of Zn, 0.1-0.5% of Ca, 0.1% of Sr, less than or equal to 0.1% of Cu and the balance of Mg. The alloy has a thermal conductivity of greater than 110W/(m.K), but a yield strength of less than 160MPa and an elongation of 5%. Although the material has higher heat conductivity, the yield strength is low, and the material can not meet the requirements of high strength and toughness and high heat conductivity of structural materials of a heat dissipation system in the fields of aerospace devices and vehicles.
Chinese patent CN110819863B discloses a low-rare earth high-heat-conductivity magnesium alloy and a preparation method thereof, and the magnesium alloy is prepared by casting Mg-Gd-Er-Zn-Zr, wherein the magnesium alloy comprises, by mass, 5.0-7.0% of Gd, 0.5-2% of Er, 3.0-7.0% of Zn, 0.5-1.0% of Zr and the balance of Mg. The thermal conductivity of the alloy is more than 115W/(m.K), the yield strength reaches 200MPa, and the elongation is more than 20%. However, a large amount of rare earth elements Gd and Er with high cost are added into the alloy, so that the alloy cost is high.
Chinese patent CN104152769B discloses a heat-conducting magnesium alloy and a preparation method thereof, and the heat-conducting magnesium alloy is prepared by the following chemical components, by mass, 0.8-3.0% of Zn, 0.25-0.48% of Mn, 0.05-1.0% of Ce, less than or equal to 0.15% of impurity, and the balance of Mg. The deformation mode is extrusion, rolling or forging. The alloy has a thermal conductivity of more than 130W/(m.K), a yield strength of more than 200MPa and an elongation of more than 20%. However, the alloy has low Zn content and insufficient mechanical strength, can only be manufactured by adopting a deformation processing technology with complex technology, and is not suitable for preparing products with complex structures by using the alloy.
In the prior art, the publication AZ91D magnesium alloy semi-solid thixotropic injection structure and process research is carried out to prepare the Mg-Al-Zn semi-solid thixotropic injection molding alloy, wherein the chemical composition of the alloy comprises 8.3 mass percent of Al, 0.54 mass percent of Zn, 0.14 mass percent of Mn and the balance of Mg. The alloy has a thermal conductivity of less than 60W/(mK), a yield strength not mentioned and an elongation of about 8%. The alloy cannot simultaneously give consideration to excellent mechanical properties and heat conduction properties, and has limited application fields.
In recent years, miniaturization and integration of electronic devices have become a development trend, which puts higher and higher demands on the heat conducting property and mechanical property of the heat dissipation/heat conduction assembly, so as to ensure that the product has high working stability and service life. Particularly, complex structural members of heat dissipation/heat conduction systems such as aerospace electronic devices, 3C products and vehicles with urgent light weight requirements are required to have high heat conductivity, excellent mechanical properties and low production cost. However, the current commercial grade magnesium alloy and the magnesium alloy materials reported at home and abroad cannot simultaneously consider the heat conducting property, the mechanical property and the processing cost, so that development of novel magnesium alloy component design and novel forming technology research is urgently needed to develop novel high-strength and high-toughness high-heat conducting magnesium alloy.
Disclosure of Invention
The invention aims to provide a high-strength high-toughness high-heat-conductivity magnesium alloy and a processing method thereof, and solves the problem that the existing magnesium alloy cannot simultaneously achieve high heat conductivity and high strength by adopting a low-cost alloy formula on the premise of not adding expensive rare earth elements. The magnesium alloy has the heat conductivity coefficient of more than or equal to 115W/(m.K), the yield strength of more than or equal to 200MPa and the elongation rate of more than or equal to 8 percent, and meanwhile, the semi-solid thixotropic injection molding technology is adopted for processing, the mechanical property of the magnesium alloy is close to that of the deformed magnesium alloy, but the technology is less difficult than the traditional plastic deformation mode, the cost is low, the large-scale mass production is convenient, the magnesium alloy product with a complex structure which cannot be manufactured by the deformation technology can be manufactured, and the magnesium alloy product can be widely used for preparing heat dissipation/heat conduction components in the fields of aerospace, 3C products and automobile parts.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
The high strength and toughness high heat conductivity magnesium alloy comprises 8.0-12.0% of Zn, less than or equal to 2.0% of Ca or Mn, less than or equal to 2.0% of Mn, and one or more of La, ce, si, sb, zr, sn%, wherein La is less than or equal to 2.0%, ce is less than or equal to 2.0%, si is less than or equal to 2.5%, sb is less than or equal to 2.0%, zr is less than or equal to 1.0%, sn is less than or equal to 2.0%, and the balance is Mg and unavoidable impurities.
The heat conductivity coefficient of the magnesium alloy is more than or equal to 115W/(m.K), the yield strength is more than or equal to 200MPa, and the elongation is more than or equal to 8%.
The research shows that the mechanical property and the heat conduction property of the magnesium alloy have close relation with the alloy components and the microstructure. The mechanism of improving mechanical properties such as solid solution strengthening, dispersion strengthening, dislocation strengthening, fine grain strengthening and the like tends to reduce the heat conducting property.
The design idea of the invention is that the mechanical property of the material is improved through a second-phase strengthening mechanism, and meanwhile, the negative influence of the added alloy element on the heat conduction property of the material is reduced to the greatest extent, so that the type and the content of the alloy element are required to be controlled, and the material has the characteristics of high strength and toughness and high heat conduction.
The Zn can obviously improve the mechanical property of the magnesium alloy, has smaller negative influence on the heat conduction property, and the trace Mn, ca, la, ce, si, sb, zr, sn element can improve the mechanical property of the magnesium alloy in a mode of refining grains or forming second phase reinforcement, and can not obviously reduce the heat conduction property.
The solid solubility of Zn element in Mg is about 6.2%, and the Mg-Zn alloy has a wider solid-liquid two-phase region. Zn element and Mg form a series of Mg-Zn binary phases, the effect of solid solution strengthening and precipitation strengthening is achieved, zn is a weak grain refining agent, a finer microstructure can be obtained, and therefore the mechanical property of the magnesium alloy is improved, and the negative influence of Zn element on the heat conducting property of the magnesium alloy is far lower than that of Al element, so that the heat conducting property of the Mg-Zn alloy is obviously superior to that of the Mg-Al alloy. The content of Zn element is too low, the fluidity of semi-solid slurry is not good, and the complete filling cannot be realized, and the addition of too much Zn element can influence the fluidity of the alloy, increase the hot cracking tendency of microstructure and reduce the heat conducting property of the alloy. Therefore, the Zn element content in the invention is 8-12%.
Mn can refine the microstructure of the magnesium alloy and improve the corrosion resistance by controlling the Fe content. The proper Mn content has less negative effect on the heat conducting property of the magnesium alloy, so the Mn element percentage content in the invention is not more than 2 percent.
Ca element has the function of grain refinement in the magnesium alloy, can inhibit oxidation of magnesium alloy melt, and improves the flame retardant property of the magnesium alloy. The element and Mg form a second phase with high melting point, and the effect of improving the mechanical property of the alloy is remarkable. The proper amount of Ca element does not obviously reduce the heat conduction performance of the magnesium alloy, so that the mass percent of the Ca element does not exceed 2 percent by adopting low alloying.
The rare earth elements La and Ce can refine the microstructure of the magnesium alloy, purify the alloy melt, improve the fluidity of the alloy and reduce the fierce tendency of the alloy. The rare earth second phase particles can obviously improve the mechanical property and the heat resistance of the magnesium alloy, and the magnesium alloy has excellent heat conductivity and mechanical property by adding a small amount of La and Ce into the magnesium alloy. Research shows that La and Ce have less negative effect on the heat conducting property of the magnesium alloy and belong to cheap rare earth, so that the mass percent of La and Ce in the invention is not more than 2%.
Si can improve the fluidity of a melt in the magnesium alloy, and a Mg 2 Si second phase formed in the solidification process is a very effective mechanical property strengthening phase so as to improve the mechanical property of the magnesium alloy. However, si element reduces the corrosion resistance of magnesium alloy, and therefore, the mass percentage of Si in the present invention is not more than 2.5%.
The solid solubility of Sb in a magnesium matrix is extremely small and mainly exists in the form of a second phase Mg 3Sb2, so that the element has little influence on the heat conducting property of the magnesium alloy, the mechanical property at normal temperature can be improved, and meanwhile, the casting property of the Mg-Zn alloy can be improved by the Sb. When the addition amount of Sb is more than 2%, a large amount of continuous network second phases are precipitated, so that the mechanical property of the magnesium alloy is reduced. Therefore, the mass percentage of Sb in the invention is 0-2%.
Zr is a strong grain refining element in magnesium alloy, and is particularly used as a good grain refiner of Mg-Zn alloy. The solid solubility of Zr in Mg is very small, and a small amount of Zr does not have obvious influence on the heat conducting property of the magnesium alloy, so that the mass percent of Zr in the invention is not more than 1%.
The Sn element, mg and Zn form a strengthening phase, so that the mechanical property of the magnesium alloy is improved, and the influence on the heat conducting property is small. The mass percentage of Sn in the invention is not more than 2 percent.
Semi-solid thixotropic injection molded alloys generally have a relatively broad solid-liquid two-phase region. The alloy semi-solid slurry must have sufficient fluidity to fill complex mold cavities while ensuring near laminar flow filling without introducing significant amounts of gas. Therefore, the high-strength and high-toughness high-heat-conductivity magnesium alloy can be formed by using a semi-solid thixotropic injection molding process, and alloying elements which are beneficial to obtaining the characteristics are also required to be added into the magnesium alloy. According to the invention, zn elements with higher content are added, when the Zn content is controlled to be 8-12%, the fluidity of the semi-solid slurry is better, complete filling can be realized, elements such as Ca, zr, mn, si, sb, sn, la, ce and the like are selected for multi-element alloying, the elements have less negative influence on the heat conducting performance of the magnesium alloy on the basis of improving the mechanical performance of the magnesium alloy, and the content of each added element is controlled below the respective solid solubility as much as possible, so that the fluidity of the semi-solid slurry is better on the premise of considering the high strength and toughness and high heat conducting performance of the alloy, and the semi-solid thixotropic injection molding process can be adopted to manufacture the magnesium alloy product with complex structure which cannot be manufactured by the deformation process.
The processing method of the high-strength high-toughness high-heat-conductivity magnesium alloy comprises the following steps:
1) Proportioning materials
Taking pure Mg ingot, pure Zn ingot, pure Sb ingot, pure Sn ingot, mg-Mn, mg-Ca, mg-La, mg-Ce, mg-Si and Mg-Zr intermediate alloy as raw materials, and proportioning according to the weight percentage of the magnesium alloy components;
2) Smelting
Placing pure Mg ingot into a crucible of a smelting furnace, heating to 700-720 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 750-770 ℃, sequentially adding one or more of pure Zn ingot, pure Sb ingot, pure Sn ingot, mg-Mn, mg-Ca, mg-La, mg-Ce, mg-Si and Mg-Zr intermediate alloy into the melted melt, fully stirring for 10-15 min after the alloy is completely melted, adding magnesium alloy flux for refining for 15-20 min, removing surface scum, and finally preserving heat for 20-30 min at 720-760 ℃ to cast into magnesium alloy ingots;
3) Magnesium alloy particle processing
Placing the magnesium alloy cast ingot into a granulator, and processing into magnesium alloy particles;
4) Semisolid thixotropic injection molding
Placing magnesium alloy particles in a charging barrel of semi-solid thixotropic injection molding equipment, heating to 550-630 ℃ to form magnesium alloy semi-solid slurry, applying shearing force to the semi-solid slurry by using a screw shearing device, and controlling the rotating speed of a screw to be 100-180 r/min;
5) Heat treatment of
The obtained semi-solid metal piece is sequentially subjected to solution treatment and aging treatment, wherein the solution treatment temperature is 300-450 ℃, the heat preservation time is 1-36 h, the aging treatment temperature is 150-200 ℃, and the heat preservation time is 4-168 h.
Preferably, in the step 2), the magnesium alloy flux is an RJ-4 flux, an RJ-5 flux or an RJ-6 flux, preferably an RJ-5 flux.
Preferably, in the step 3), the particle size of the magnesium alloy is (1 to 2 mm) × (4 to 6 mm).
Preferably, in the step 4), the solid phase ratio of the semi-solid slurry is controlled to be 10-50% by volume.
In the semi-solid thixotropic injection molding process, the temperature of the charging barrel is set at 550-630 ℃ so as to realize the solid phase ratio of semi-solid slurry meeting the semi-solid thixotropic injection molding process, and the solid phase ratio of the semi-solid slurry is controlled at 10-50% by volume, so that the material has higher strength and heat conducting property. The injection speed is 2-5 m/s, the injection speed is too low, the material cannot be completely filled, the injection speed is too high, the porosity of the material is higher, and the mechanical property and the heat conducting property are reduced. In addition, aiming at the alloy design in the invention, the temperature of the die is set at 200-300 ℃, so that the thermal cracking is prevented, the complete filling is realized, and the qualified magnesium alloy product is manufactured.
The invention increases the heat treatment technology after the semi-solid thixotropic injection molding to further improve the strength and toughness and other excellent performances of the magnesium alloy, has small porosity and fine grains, but still has coarser second phase, separates out the second phase with smaller size after the heat treatment, increases the strengthening effect of the second phase and improves the mechanical property of the material, and in addition, ensures that the tiny second phase is separated out after the alloy element is completely dissolved into the magnesium matrix after the heat treatment, reduces the negative influence of the alloy element on the heat conducting property of the magnesium alloy and improves the heat conductivity. Therefore, a heat treatment process is added after semi-solid thixotropic injection molding, and the mechanical property and the heat conduction property of the material are improved simultaneously by utilizing solid solution strengthening and aging strengthening.
The solid solution treatment temperature is 300-450 ℃, the heat preservation time is 1-36 h, and the aim is to ensure that alloy elements Zn, si, sb, sn, ca, la, ce, zr are completely dissolved into a magnesium matrix as far as possible, and the grain size can not be obviously grown by controlling. The aging treatment temperature is 150-200 ℃, the heat preservation time is 4-168 h, and the aging treatment temperature and time ensure that fine second phases of Mg-Zn, mg-Si, mg-Sb, mg-Sn, mg-Ca and other binary strengthening phases and Mg-Zn-La, mg-Zn-Ce, mg-Zn-Ca and other ternary strengthening phases are separated out.
After semi-solid treatment, the magnesium alloy is subjected to heat treatment, and through solution treatment and aging treatment, a tiny and dispersed second phase can be separated out, so that the mechanical property of the material is obviously improved; the alloy provided by the invention has the advantages that the binary strengthening phases such as Mg-Zn, mg-Si, mg-Sb, mg-Sn, mg-Ca and the like and the ternary strengthening phases such as Mg-Zn-La, mg-Zn-Ce, mg-Zn-Ca and the like which are separated out after heat treatment are adopted, so that the mechanical properties of the material are improved, and meanwhile, the lattice distortion degree is reduced and the thermal conductivity of the material is improved through solution treatment and aging treatment. Therefore, the heat treatment mode of solution treatment and aging treatment can improve the mechanical property and the heat conduction property of the material at the same time.
The traditional die-casting magnesium alloy is cast by adopting a die-casting process, no matter what components are, the interior of the magnesium alloy can generate high porosity, so that the mechanical property and the heat conducting property of the magnesium alloy are reduced, and the mechanical property and the heat conducting property of the material cannot be improved by heat treatment in the follow-up process due to the high porosity of the interior of the magnesium alloy.
The traditional deformation magnesium alloy adopts a deformation process, so that the magnesium alloy can obtain excellent heat conduction performance and mechanical property, the deformation process comprises extrusion, forging, rolling and the like, but the magnesium alloy is internally provided with a close-packed hexagonal crystal structure, so that when the magnesium alloy product is manufactured by adopting the deformation process, the process is more complex, the cost is higher, and the magnesium alloy product with complex structure cannot be prepared.
The invention adopts the semi-solid thixotropic injection molding and heat treatment process, combines the component control of the magnesium alloy, effectively balances the mechanical property and the heat conduction property of the magnesium alloy, and ensures that the magnesium alloy material has high strength and toughness and high heat conduction.
The invention has the beneficial effects that:
1. The high-strength and high-toughness high-heat-conductivity magnesium alloy disclosed by the invention takes conventional alloy elements Zn, ca or/and Mn as basic elements, a small amount of La, ce, si, sb, zr, sn elements are added, the mechanical properties of the material are improved through a second-phase strengthening mechanism, meanwhile, the addition amount of La, ce, si, sb, zr, sn elements is controlled, the negative influence of the added alloy elements on the heat-conducting property of the material is reduced to the greatest extent, and the obtained magnesium alloy has high heat conductivity and high strength at the same time without adding any expensive rare earth elements, wherein the heat conductivity coefficient of the magnesium alloy is more than or equal to 115W/(m.K), the yield strength is more than or equal to 200MPa, and the elongation is more than or equal to 8%.
2. The invention adopts Zn element with higher content in component design, selects elements such as Ca, zr, mn, si, sb, sn, la, ce to carry out multi-element alloying, controls the content of each added element to be lower than the respective solid solubility, controls the semisolid slurry of the alloy to have enough fluidity on the basis of ensuring the high mechanical property and the heat conducting property of the magnesium alloy, can be molded by adopting a semisolid thixotropic injection molding process to fill a complex mold cavity, ensures to be close to laminar flow filling without involving more gas, and can be used for manufacturing complex structural magnesium alloy products which cannot be manufactured by a deformation process and complex structural members of heat dissipation/heat conducting systems such as aerospace electronic devices, 3C products and vehicles.
3. The invention adopts semi-solid thixotropic injection molding technology, realizes complete filling by controlling heating temperature, injection speed and mold temperature, and produces qualified magnesium alloy products, and the semi-solid thixotropic injection molding is followed by adding a heat treatment process, and the mechanical property and heat conduction property of magnesium alloy are further improved simultaneously by utilizing solid solution strengthening and aging strengthening. The mechanical property of the obtained magnesium alloy is close to that of the deformed magnesium alloy, but the magnesium alloy has higher heat conduction property, and the process has smaller difficulty than the traditional solid plastic deformation mode, has low cost, is convenient for large-scale mass production, and can be used for manufacturing magnesium alloy products with complex structures which cannot be manufactured by the deformation process.
Detailed Description
The technical scheme of the present invention is described in detail below by examples, which are given as detailed embodiments and specific operation procedures on the premise of the technical scheme of the present invention, but the scope of protection of the present invention is not limited to the examples below.
The magnesium alloy composition of the present example is shown in table 1, and the balance is Mg and unavoidable impurities.
Example 1
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 10.3 weight percent of Zn,0.3 weight percent of Mn,1.5 weight percent of Ca,0.5 weight percent of La and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Mn, mg-Ca and Mg-La intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 713 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 750 ℃, sequentially adding pure Zn ingot, mg-Mn, mg-Ca and Mg-La intermediate alloy into the melted melt, fully stirring for 12min after the alloy is completely melted, adding RJ-5 flux, refining for 20min, removing surface scum, and finally preserving heat for 20min at 730 ℃ to cast into magnesium alloy ingots;
3) Placing a magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1mm multiplied by 5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 580 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 130r/min, and injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 3m/s, and the temperature of the mold is 240 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 320 ℃, the heat preservation time is 8 hours, the aging treatment temperature is 170 ℃, and the heat preservation time is 120 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 2
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 11.2 weight percent of Zn,0.5 weight percent of Ca,0.1 weight percent of La,0.8 weight percent of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Ca, mg-La and Mg-Ce intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 700 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding pure Zn ingot, mg-Ca, mg-La and Mg-Ce intermediate alloy into the melted melt, fully stirring for 10min after the alloy is completely melted, adding RJ-4 flux, refining for 19min, removing surface scum, and finally preserving heat for 20min at 720 ℃ to cast a magnesium alloy ingot;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1mm multiplied by 1.5mm multiplied by 4 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 570 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 120r/min, and injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 3.6m/s, and the temperature of the mold is 220 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy, wherein the solution treatment temperature is 335 ℃, the heat preservation time is 36h, the aging treatment temperature is 180 ℃, and the heat preservation time is 96h.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 3
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 11.8wt% of Zn,0.1wt% of Ca,0.2wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Ca and Mg-Ce intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 709 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding pure Zn ingot, mg-Ca and Mg-Ce intermediate alloy into the melted melt, fully stirring for 11min after the alloy is completely melted, adding RJ-5 flux for refining for 15min, removing surface scum, preserving heat for 20min at 735 ℃, and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 2mm multiplied by 1.2mm multiplied by 5.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 590 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 150r/min, and injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 3.8m/s, and the temperature of the mold is 230 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 450 ℃, the heat preservation time is 1h, the aging treatment temperature is 175 ℃, and the heat preservation time is 75h.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 4
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 8.3 weight percent of Zn,1.3 weight percent of Ca,0.6 weight percent of Zr and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Ca and Mg-Zr intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percent of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 713 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding pure Zn ingot, mg-Ca and Mg-Zr intermediate alloy into the melted melt, fully stirring for 10min after the alloy is completely melted, adding RJ-5 flux for refining for 16min, removing surface scum, preserving heat for 20min at 740 ℃, and casting into magnesium alloy ingots;
3) Placing a magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.5mm multiplied by 4 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 570 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 120r/min, injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 4m/s, and the temperature of the mold is 260 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semi-solid magnesium alloy piece, wherein the solution treatment temperature is 350 ℃, the heat preservation time is 26 hours, the aging treatment temperature is 160 ℃, and the heat preservation time is 50 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 5
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 10.1wt% of Zn,1.5wt% of Mn,1.0wt% of Sn and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, pure Sn ingots and Mg-Mn intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 710 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 765 ℃, sequentially adding pure Zn ingot, mg-Mn, mg-Ca and Mg-La intermediate alloy into the melted melt, fully stirring for 14min after the alloy is completely melted, adding RJ-5 flux for refining for 18min, removing surface scum, and finally preserving heat for 20min at 740 ℃ and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.2mm multiplied by 2.0mm multiplied by 4.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 550 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 150r/min, injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, the injection speed is 3.8m/s, and the temperature of the mold is 260 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 340 ℃, the heat preservation time is 32 hours, the aging treatment temperature is 150 ℃, and the heat preservation time is 168 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 6
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 10.9wt% of Zn,2.0wt% of Ca,1.5wt% of Si and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Ca and Mg-Si intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 718 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding pure Zn ingot, mg-Ca and Mg-Si intermediate alloy into the melted melt, fully stirring for 11min after the alloy is completely melted, adding RJ-6 flux for refining for 20min, removing surface scum, preserving heat for 20min at 730 ℃, and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.6mm multiplied by 1.8mm multiplied by 5.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 560 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 150r/min;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 325 ℃, the heat preservation time is 2 hours, the aging treatment temperature is 190 ℃, and the heat preservation time is 150 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 7
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 9.5wt% of Zn,2.0wt% of Mn,0.3wt% of La,0.8wt% of Sb and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, pure Sb ingots, mg-Mn and Mg-La intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 715 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 755 ℃, sequentially adding pure Zn ingot, mg-Mn, mg-Ca and Mg-La intermediate alloy into the melted melt in sequence, fully stirring for 15min after the alloy is completely melted, adding RJ-5 flux for refining for 15min, removing surface scum, and finally preserving heat for 20min at 730 ℃ and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 2.0mm multiplied by 4.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 570 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 160r/min, and injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 2.8m/s, and the temperature of the mold is 210 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 320 ℃, the heat preservation time is 36h, the aging treatment temperature is 200 ℃, and the heat preservation time is 4h.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 8
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 8.0wt% of Zn,0.2wt% of Mn,1.2wt% of Ca,0.2wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Mn, mg-Ca and Mg-Ce intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 720 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding pure Zn ingot, mg-Mn, mg-Ca and Mg-Ce intermediate alloy into the melted melt, fully stirring for 10min after the alloy is completely melted, adding RJ-5 flux for refining for 16min, removing surface scum, and finally preserving heat for 20min at 750 ℃ and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.3mm multiplied by 1.9mm multiplied by 4.8 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 580 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 120r/min;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 300 ℃, the heat preservation time is 20 hours, the aging treatment temperature is 185 ℃, and the heat preservation time is 120 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 9
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 11.3 weight percent of Zn,1.1 weight percent of Mn,1.3 weight percent of Ce,0.5 weight percent of Sb and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, pure Sb ingots, mg-Mn and Mg-Ce intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting a pure Mg ingot into a crucible of a smelting furnace, heating to 705 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 760 ℃, sequentially adding a pure Zn ingot, a pure Sb ingot, mg-Mn and Mg-Ce intermediate alloy into the melted melt, fully stirring for 13min after the alloy is completely melted, adding RJ-5 flux, refining for 19min, removing surface scum, and finally preserving heat for 20min at 720 ℃ to cast a magnesium alloy ingot;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.4mm multiplied by 1.3mm multiplied by 5.2 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 570 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 150r/min, injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 2.8m/s, and the temperature of the mold is 220 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy, wherein the solution treatment temperature is 315 ℃, the heat preservation time is 28h, the aging treatment temperature is 200 ℃, and the heat preservation time is 40h.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Example 10
1) The high-plasticity heat-conducting magnesium alloy is designed and selected to contain 12.0wt% of Zn,0.3wt% of Ca,0.9wt% of La and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Ca and Mg-La intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 700 ℃, completely melting under the protection of mixed shielding gas of CO 2 and SF 6, heating to 770 ℃, sequentially adding pure Zn ingot, mg-Ca and Mg-La intermediate alloy into the melted melt, fully stirring for 10min after the alloy is completely melted, adding RJ-5 flux for refining for 15min, removing surface scum, preserving heat for 20min at 760 ℃, and casting into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.7mm multiplied by 1.6mm multiplied by 4.4 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 580 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 120r/min, and injecting the magnesium alloy semi-solid slurry into a mold to form a semi-solid part after the shearing is finished, wherein the injection speed is 2.5m/s, and the temperature of the mold is 210 ℃;
5) And sequentially carrying out solution treatment and aging treatment on the semisolid magnesium alloy piece, wherein the solution treatment temperature is 410 ℃, the heat preservation time is 4 hours, the aging treatment temperature is 190 ℃, and the heat preservation time is 60 hours.
The properties of the obtained magnesium alloy parts are shown in Table 2.
Comparative example 1
The magnesium alloy comprises 9wt% of Al,1wt% of Zn and the balance of Mg.
The alloy is designed and proportioned according to the mass percentages of the elements by taking pure Mg ingots, pure Al ingots and pure Zn ingots as raw materials. Adding pure Mg ingot into a crucible furnace protected by CO 2+SF6 gas, heating to 720 ℃ after the pure Mg ingot is completely melted, sequentially adding pure Al ingot and pure Zn ingot after the temperature is raised to 760 ℃, fully stirring for 10 minutes after the alloy is completely melted, adding RJ-5 flux for refining for 15 minutes, removing surface scum, preserving heat and standing for 20 minutes at 720-760 ℃, transferring to a die casting machine heat preservation furnace, and carrying out die casting on a magnesium alloy die casting machine, wherein the temperature of a melt is 650 ℃ and the temperature of a die is 250 ℃ to obtain an AZ91D die casting.
The heat conductivity and mechanical properties of the alloy are shown in Table 2, the heat conductivity of the alloy is 55W/(m.K), the tensile strength is 256MPa, the yield strength is 150MPa, and the elongation is 4.5%.
Comparative example 2
The magnesium alloy comprises 6wt% of Al,0.5wt% of Mn and the balance of Mg.
The alloy is designed and proportioned according to the mass percentages of the elements by taking pure Mg ingots, pure Al ingots and Mg-Mn intermediate alloy as raw materials. Adding pure Mg ingot into a crucible furnace protected by CO 2+SF6 gas, heating to 720 ℃ until the pure Mg ingot is completely melted, sequentially adding pure Al ingot and Mg-Mn intermediate alloy after the temperature is raised to 760 ℃, fully stirring for 10 minutes after the alloy is completely melted, adding RJ-5 for refining for 15 minutes, removing surface scum, keeping the temperature at 720-760 ℃ and standing for 20 minutes, and finally casting into magnesium alloy ingots. Transferring to a heat preservation furnace of a die casting machine, die casting on a magnesium alloy die casting machine, and obtaining the AM60B die casting at the temperature of 660 ℃ and 250 ℃ of a melt.
The heat conductivity and mechanical properties of the alloy are shown in Table 1, the heat conductivity of the alloy is 63W/(m.K), the tensile strength is 230MPa, the yield strength is 132MPa, and the elongation is 12%.
As shown in Table 2, compared with the traditional AZ91D magnesium alloy and AM60B magnesium alloy, the yield strength and the tensile strength of the magnesium alloy are obviously improved, the heat conductivity of the magnesium alloy is also obviously improved, the heat conductivity of the magnesium alloy is more than or equal to 115W/(m.K), and the heat conductivity of the traditional AZ91D magnesium alloy and AM60B magnesium alloy is only about 60W/(m.K).
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