CN103352978B - Al3Ti/Al3Ni particle synergistically reinforced silicon-aluminum matrix composite piston and its preparation method - Google Patents

Abstract

The invention discloses Al ₃ti/Al ₃ni particle is collaborative strengthens sial base composite piston and preparation method.Disclosed composite piston comprises piston only and is located at the enhancing wearing layer in the end of piston only and circular groove region surface, and piston only material is silico-aluminum, the Al that the material strengthening wearing layer is silico-aluminum and is distributed in silico-aluminum ₃ti particle and Al ₃ni particle.Disclosed preparation method arranges graphite paper at Piston mould inwall, graphite paper is placed Ti-Ni alloy silk screen, afterwards, under electromagnetic field effect, in Piston mould, pour into a mould silumin alloy melt, after silico-aluminum solidifies, stop applying electromagnetic field, finally by forging, heat treatment, machining and grinding process, obtain composite piston.Composite piston oxidative stability of the present invention and wear resistance better.

Description

Al3Ti/Al3Ni particle synergistically reinforced silicon-aluminum matrix composite piston and its preparation method

technical field

The invention relates to a high-silicon-aluminum-based piston, in particular to an in-situ synthesized Al ₃ Ti/Al ₃ Ni particle synergistically reinforced silicon-aluminum-based composite piston by an electromagnetic field method and a preparation method thereof.

Background technique

In recent years, with the development of lightweight automobiles, more and more automobiles have adopted aluminum-based material engines. Pistons are important components in the engine. The piston materials used mainly include cast iron, cast steel, aluminum alloy, and newly developed Piston materials, such as aluminum matrix composite materials, ceramic materials, carbon materials, heat-resistant magnesium alloy materials, magnesium matrix composite materials, etc. At present, the most researched and used Al-Si multi-component alloys have experienced the development process of hypoeutectic, eutectic, and hypereutectic in terms of composition selection, and Al-Si piston products mostly adopt gravity metal mold casting, low-pressure metal casting, etc. Casting, squeeze casting and semi-solid forming techniques.

When the piston is working, the reciprocating motion of the annular groove of the piston and the piston, the piston skirt and the cylinder wall constitute friction pairs respectively. The end of the piston is directly in contact with the high-temperature and high-pressure gas, which bears a large thermal load and mechanical load, and because it reciprocates at a high speed in the cylinder liner with extremely poor lubrication conditions, it bears a huge inertial force. Therefore, the piston ring groove, piston The skirt and the end of the piston wear rapidly, and the failure of the piston is mainly due to the failure of the piston ring groove and the end of the piston. In order to improve the service life of the piston, a particle-reinforced aluminum-based composite piston has been developed, that is, the use of high-hardness, high-modulus ceramic particles to enhance the easy-to-failure parts of the piston to improve the life of the piston. At present, SiC particles are mainly added to the molten In the matrix material, the composite piston is obtained by casting under the action of gravity or external force, but the defect of the composite piston prepared by this method of adding particles is: the interface between the particle and the matrix is poorly bonded, and the bonding force is low. During use, The reinforced phase is easy to fall off, and secondly, the reinforced phase is unstable and easy to decompose at high temperature. Based on this, a preparation technology for preparing composite pistons by in-situ synthesis is developed, that is, the desired reinforcement is formed in the system. The characteristic is that the reinforcement is not introduced from the outside, but is nucleated and grown in the metal matrix Obtain a reinforced phase with no pollution on the surface, high bonding strength with the matrix interface, and relatively stable thermodynamics, ensuring better interface bonding between the reinforcing particles and the matrix, as well as good thermodynamic stability in the matrix, which is conducive to working under high temperature conditions. Fields of application of particle reinforced composite pistons.

One of the objectives of the present invention is to provide an Al ₃ Ti/Al ₃ Ni particle synergistically reinforced silicon-aluminum matrix composite piston.

Correspondingly, the Al ₃ Ti/Al ₃ Ni particle synergistically reinforced silicon-aluminum matrix composite piston provided by the present invention includes a piston body and an enhanced wear-resistant layer arranged on the end of the piston body and the surface of the annular groove area, and the material of the piston body It is silicon-aluminum alloy, and the material of the enhanced wear-resistant layer is Al ₃ Ti, Al ₃ Ni and silicon-aluminum alloy.

The material of the enhanced wear-resistant layer is Al ₃ Ti particles, Al ₃ Ni particles, silicon aluminum alloy between Al ₃ Ti particles and Al ₃ Ni particles.

The thickness of the enhanced wear-resistant layer is 1-5mm.

The enhanced wear-resistant layer is prepared from titanium-nickel alloy wire with a molar ratio of Ti to Ni of (1-10):(1-10).

The diameter of the titanium-nickel alloy wire is 50-150 μm.

Another object of the present invention is to provide a method for preparing the above-mentioned Al ₃ Ti/Al ₃ Ni particle synergistically reinforced silicon-aluminum matrix composite piston. The method is specifically to synthesize Al ₃ Ti/Al ₃ Ni particles in situ under the action of an electromagnetic field.

The method includes the following steps:

Graphite paper is arranged on the inner wall of the piston mold, and a titanium-nickel alloy wire mesh is placed on the graphite paper. After that, in the electromagnetic field, the silicon-aluminum alloy melt is poured into the piston mold. After the silicon-aluminum alloy is solidified, the electromagnetic field is stopped to obtain a semi-finished product;

Forging, heat treatment, machining and grinding of semi-finished products;

Then get the finished product.

The titanium-nickel alloy wire mesh is a 20-100 mesh titanium-nickel alloy wire mesh.

The frequency of the electromagnetic field is 2000-3000 Hz, and the power is 20-30 KW.

In the above preparation method, when the silicon-aluminum alloy melt begins to solidify, the intensity of the electromagnetic field is reduced, and the power of the electromagnetic field is gradually reduced during the solidification process of the silicon-aluminum alloy, and the power of the electromagnetic field is reduced to zero after the silicon-aluminum alloy melt is completely solidified.

Compared with prior art, the present invention has following advantage:

(1) The end of the piston and the annular groove are the reinforced areas formed by the Al ₃ Ti/Al ₃ Ni particles and the aluminum matrix formed in situ during the solidification of the alloy, which has good wear resistance and high temperature oxidation resistance; the piston The skirt and the pin hole are non-reinforced areas without particles, which have good tensile strength; a metallurgical bond is formed between the reinforced area and the non-reinforced area;

(2) Uniform distribution of reinforcement: The selection of titanium-nickel alloy wire mesh with micron-scale diameter lays the foundation for in-situ reaction to generate uniformly distributed Al ₃ Ti/Al ₃ Ni particle reinforcement, while saving a lot of precious metals.

(3) The effect of applying electromagnetic field: ①The casting mold and the titanium-nickel alloy wire are both magnetically conductive materials. Applying an electromagnetic field can quickly preheat the casting mold to avoid the formation of solidified shells caused by the low temperature of the casting mold and the wire mesh; ②It can refine the grain (3) It can evenly distribute the two kinds of particles synthesized by in-situ reaction; (4) In the particle-reinforced composite zone, the matrix is a spherical α-Al matrix. When remelted and heated to 550-570 , good thixotropy, suitable for forging and forming, and conducive to tissue densification.

(4) Strong binding force: The interface between the in-situ synthesized reinforcement and the matrix is clean and firmly bonded, which can transmit stress very effectively, ensure the wear resistance and high-temperature mechanical properties of the composite material, and prolong the service life of the piston.

(5) Enhanced oxidation resistance: The outer surface of the composite piston contains a large amount of Al ₃ Ti/Al ₃ Ni reinforcement, which forms a dense alumina film at high temperature, rather than a mixed film formed by alumina and titanium oxide, showing Good antioxidant properties;

(6) Good wear resistance: A large number of Al ₃ Ti/Al ₃ Ni reinforcements not only have good bonding force with the matrix, but also have high hardness.

(7) The parameter density of the composite piston prepared by the method of the present invention is 1.9-2.3g/cm ³ ; the bending strength is 90-115Mpa; the expansion coefficient is (7-9)× ^10-6 /°C; the friction coefficient is 0.035- 0.074; thermal conductivity 80‐140W/mK.

A preferred preparation method of Al ₃ Ti/Al ₃ Ni particle synergistically reinforced aluminum matrix composite piston includes the following steps:

(1) Arrange a layer of graphite paper on the inner wall of the piston mold, and then arrange the titanium-nickel alloy wire mesh close to the graphite paper;

(2) Apply an electromagnetic field with a frequency of 2000-3000Hz and a power of 20-30KW before pouring, and preheat the piston mold and titanium-nickel alloy wire mesh to 200-300°C;

Then pour the molten silicon-aluminum alloy solution into the piston mold, the pouring temperature is 700-760°C, and the flow rate of the silicon-aluminum alloy solution is 5-15Kg/min;

After pouring for 5-10 minutes, reduce the electromagnetic field power at a rate of 3-5KW/min until the silicon-aluminum alloy melt is completely solidified, then stop applying the electromagnetic field to obtain a cast composite piston;

(3) Heat the as-cast composite piston to 550°C to 570°C for remelting, then send it into the forging mold cavity of the forging die machine, and perform thixotropic forging treatment to obtain the forged composite piston. The preheating temperature in the mold cavity during forging is For: 100～300℃, forging deformation speed is 5～15mm/s;

(4) Treat the forged composite piston at 450-500°C for 8-10 hours, and then at 150-200°C for 3-6 hours;

Machining and grinding the piston treated in step (4) to obtain a silicon-aluminum matrix composite piston reinforced by Al ₃ Ti/Al ₃ Ni particles synergistically.

Among the above-mentioned preferred preparation methods:

The function of graphite paper is mainly to avoid the adhesion between the melt and the mold, if the connection is made, the surface of the casting will be rough.

After pouring, continue to apply the electromagnetic field, and under the action of induction heating, the liquid aluminum liquid reacts with the solid titanium-nickel alloy wire mesh to form Al ₃ Ti/Al ₃ Ni intermetallic compound particles, which are evenly distributed on the piston. The end and the ring groove area; after reacting for 5 to 10 minutes, reduce the electromagnetic power at a rate of 3 to 5 KW/min until the molten metal is completely solidified, stop applying the electromagnetic field, take out the casting from the mold, and cool to room temperature to obtain two These particles synergistically reinforce the as-cast aluminum-based composite piston; during this process, the solidification of the as-cast composite piston is carried out under the action of an electromagnetic field. According to the principle of semi-solid forming, the structure of the matrix is mainly spherical α-Al, which is conducive to thixotropic forging treatment. ; and the melt is in a strong mixed convective state under the action of the Loren magnetic force generated by the external electromagnetic field, the heat transfer and mass transfer speed are significantly improved, the contact opportunity between the high-temperature aluminum liquid and the titanium-nickel alloy wire is increased, and the reaction interface is expanded. The number of reinforcement phase Al ₃ Ti and Al ₃ Ni particles increases; and the Al ₃ Ti reinforcement synthesized by the in situ reaction can be transformed into an L12 structure through the alloying element Ni, and the room temperature brittleness of the Al ₃ Ti after alloying is greatly improved. improvement, thereby improving the toughness of the composite material.

The composite piston prepared by the above preferred method has uniform and dense microstructure, fine grains, good thermal conductivity and low thermal expansion coefficient, improved high temperature resistance, tensile strength: 280-300MPa, hardness: HB>100 , compared with a single silicon-aluminum alloy piston, the wear resistance is increased by 1.5 to 2.0 times, and the oxidation resistance in the range of 400 to 500 ° C is increased by about one time. Compared with the cast iron piston, the mass is reduced by 2 to 3 times, which can greatly improve the efficiency of the piston internal combustion engine, reduce the weight of the engine, and reduce fuel consumption and emissions.

Compared with the silicon-aluminum alloy piston cast by superheated liquid melt, the composite piston manufactured by the above-mentioned preferred method has a certain volume fraction of spherical primary solid phase in the semi-solid metal, which can be remelted and heated and facilitates thixotropic forging treatment, reducing pores in the structure , composition segregation and other defects, greatly improving the compactness of the organization.

Description of drawings

Figure 1 is a reference schematic diagram of the local structure during the preparation process of the Al ₃ Ti/Al ₃ Ni particle synergistically reinforced aluminum matrix composite piston of the present invention;

Fig. 2 is the microstructure diagram of the as-cast composite piston prepared in embodiment 1;

Fig. 3 is the microstructure diagram of the as-cast composite piston prepared in embodiment 2;

Fig. 4 is the microstructure diagram of the as-cast composite piston prepared in embodiment 3;

In the figure: 1-electromagnetic induction coil, 2-mold, 3-titanium-nickel alloy wire mesh.

Detailed ways

Compared with ceramic particles, Al‐Ti and Al‐Ni intermetallic compounds not only have low density, high hardness and high melting point, but also have a similar lattice structure and similar thermal expansion coefficient to the metal Al matrix, In the present invention, two kinds of intermetallic compound particles, Al ₃ Ti and Al ₃ Ni, are added to the mature high-strength silicon-aluminum piston matrix to improve the anti-friction and wear performance on the one hand, and reduce the thermal expansion coefficient and increase the thermal conductivity on the other hand, thereby Ensure the high temperature resistance performance of the composite piston.

The present invention combines the characteristics of Al ₃ Ti, Al ₃ Ni intermetallic compounds, electromagnetic induction preheating effect, liquid-solid reaction, forging forming, etc., and provides an in-situ synthesis of Al ₃ Ti/Al ₃ Ni particles synergistically reinforced by applying an electromagnetic field. An aluminum-based composite piston and a preparation method thereof are used to more effectively meet the requirements of piston wear resistance and high-temperature mechanical properties.

The invention discloses an Al ₃ Ti/Al ₃ Ni particle synergistically reinforced silicon-aluminum matrix composite piston and a preparation method. The disclosed composite piston includes a piston body and an enhanced wear-resistant layer arranged on the end of the piston body and the surface of the annular groove area. The material of the piston body is silicon aluminum alloy, and the material of the enhanced wear-resistant layer 3 (refer to Figure 1) is silicon Aluminum alloy and Al ₃ Ti particles and Al ₃ Ni particles distributed in silicon-aluminum alloy, the thickness of which is 1-5mm; the two kinds of Al ₃ Ti/Al ₃ Ni particles are made of titanium-nickel alloy wire and silicon-aluminum alloy The aluminum matrix in the body is obtained by in-situ reaction under the action of the electromagnetic induction coil 1 (refer to FIG. 1 ).

The reinforcing phase of the present invention comes from the wire mesh woven by titanium-nickel alloy wires, only the end of the piston and the annular groove area are strengthened, which greatly saves resources; about the titanium-nickel alloy wire mesh used in the method: the Ti atom and the Ni The atomic molar ratio is (1-10): (1-10), and the titanium-nickel alloy wire with a diameter of 50-150 μm is woven into a mesh with a mesh size of 20-100 mesh, and then according to the piston end and the annular groove to be reinforced. Shape, size and thickness, select the appropriate number of layers of alloy wire mesh, and cut and superimpose it to obtain a barrel-shaped titanium-nickel alloy wire mesh with a bottom surface;

The carbon content of the piston mold used in the preparation method of the present invention is less than 0.30%, the magnetic permeability is 1000-3000, and the wall thickness of the mold can be selected between 10-15mm.

The silicon-aluminum alloy of the piston body material of the present invention, according to the requirements of the piston base material, determines the chemical composition of the silicon-aluminum base material, and melts the silicon-aluminum alloy at 750-820°C.

The following are specific examples given by the inventors. It should be noted that the present invention is not limited to these examples. Within the scope of the present invention, qualified Al ₃ Ti/Al ₃ Ni particles with synergistically reinforced high Silicon-aluminum matrix composite piston.

Example 1:

The size of the piston prepared in this example is 150 mm in outer diameter, and the reinforced layer of the piston end and the annular groove is 2-3 mm thick Al ₃ Ti/Al ₃ Ni two kinds of intermetallic compound particles reinforced silicon-aluminum matrix composite material, in which Al The molar ratio of ₃ Ti/Al ₃ Ni is 10:1, and the silicon-aluminum-based alloy matrix material is: silicon: 18.0, copper: 4.0, magnesium: 0.7, zinc: 0.2, nickel: 1.0, iron: 1.0, and the rest is aluminum.

The preparation process steps of the present embodiment are as follows:

The first step is to weave a titanium-nickel alloy wire with a Ti/Ni content of 10:1 and a diameter of 150 μm into a titanium-nickel alloy wire mesh with a mesh size of 100 mesh, and then according to the thickness of the area to be reinforced on the outer surface of the piston, Shape and size, cut three discs with a diameter of about 200mm, and overlap them to make a drum-shaped wire mesh prefabricated body with a diameter of Ф150mm×50mm;

The second step is to prepare the piston mold according to the size and shape of the piston;

The third step is to arrange the graphite paper and the titanium-nickel alloy wire mesh prefabricated body: referring to Figure 1, the graphite paper and the titanium-nickel alloy wire mesh 3 prefabricated body obtained in step 1 are respectively arranged in the piston mold 1, and the graphite paper is located on the inner wall of the mold Between the prefabricated body and the prefabricated body, the position of the prefabricated body is the corresponding position of the piston end and the annular groove to be reinforced in the low carbon steel mold;

The fourth step is to melt the piston base material at 790-820°C and let it stand for 15 minutes to obtain the molten piston base material;

The fifth step is to apply an electromagnetic field with a frequency of 3000Hz and a power of 30KW three minutes before pouring, and use the electromagnetic field to preheat the casting mold and the screen preform to 200-300°C, so as to avoid encountering a cold casting mold when pouring the melt. Cause the formation of a solidified shell, and then pour the molten molten metal of the piston base into the piston low-carbon steel mold obtained in step 3, wherein the pouring temperature is 740-760°C, and the flow rate of the molten metal is 10Kg/min;

The sixth step, after pouring, continue to apply the electromagnetic field, under the action of induction heating, the metal aluminum liquid close to the inner wall of the casting wall is still in the liquid phase region, and the liquid phase aluminum liquid reacts with the solid titanium-nickel alloy wire to form Al ₃ Ti Intermetallic compounds, the formed particles are distributed on the inner wall of the mold (mainly referring to the end of the piston and the annular groove area), after 5‐10min, reduce the power of the electromagnetic field at a speed of 5KW/min, and stop applying the electromagnetic field after it is completely solidified, and get Intermetallic compound reinforced silicon aluminum matrix cast composite piston;

Step 7: Acquisition of forged composite piston: Remelt the cast composite piston in a resistance furnace and heat it to 560±5°C, and then send it into the forging mold cavity of the forging machine for thixotropic forging to obtain a dense structure The forged composite piston, the mold preheating temperature during forging is 250°C, and the forging deformation speed is 10mm/s;

Step 8: Acquisition of heat-treated composite pistons: place the semi-finished pistons processed in step 7 at 480±5°C for 10 hours, and then at 155±5°C for 5 hours;

The ninth step, machining and grinding treatment: machining and grinding the heat-treated composite piston obtained in step eight, to obtain an Al ₃ Ti particle-reinforced aluminum-based composite piston.

The parameter density of the composite piston prepared in this example is 2.1g/cm ³ , the bending strength is 105Mpa, the expansion coefficient is (7‐9)× ^10‐6 /°C, the friction coefficient is 0.055‐0.070, and the thermal conductivity is 110‐130W /mK, the hardness is HB>100, compared with a single silicon-aluminum alloy piston, the wear resistance is increased by more than 1.8 times, and the oxidation resistance in the range of 400-500 ° C is increased by about 1 time.

Compared with cast iron pistons, the mass is reduced by about 2/3. The antioxidant performance in the range of 400-500 °C is about 1 times higher.

The microstructure diagram of the enhanced wear-resistant zone of the as-cast composite piston prepared in this embodiment is shown in FIG. 2 . In Figure 2, a large number of gray particles in the upper composite zone are Al ₃ Ti particles, and a small amount of white particles and rod-like structures are Al ₃ Ni particles. The area without particles in the lower part is the silicon-aluminum alloy matrix area.

Example 2:

In this example, an aluminum-based composite piston with an outer diameter of 100 mm is prepared, and its reinforcing layer is Al ₃ Ti/Al ₃ Ni intermetallic compound particle-reinforced aluminum-based composite material with a thickness of 1 to 2 mm, in which Al ₃ Ti/Al ₃ The fraction ratio of Ni is 4:1, the base material is A390 high-silicon aluminum alloy, the chemical composition is: silicon: 17.0, copper: 4.5, magnesium: 0.6, zinc: 0.1, nickel: 0.7, iron: 0.5, and the rest is aluminum .

This example differs from Example 1 in that: (1) the ratio of the reinforcement Al ₃ Ti/Al ₃ Ni is different; (2) the chemical composition of the matrix is different, mainly referring to the content of silicon; (3) the thickness of the reinforcement different.

Weave titanium-nickel alloy wire with a Ti/Ni content atomic ratio of 4:1 and a diameter of 50 μm into a wire mesh with a mesh size of 60 mesh, and then cut two diameters according to the thickness, shape and size of the area to be reinforced on the outer surface of the piston. A circular mesh of about 150mm is overlapped to make a drum-shaped wire mesh prefabricated body, and the size of the drum is Ф100mm×50mm;

Melt the piston base material at 750-780°C and let it stand for 10 minutes to obtain the molten piston base material;

Three minutes before pouring, apply an electromagnetic field with a frequency of 2500Hz and a power of 25KW, use the electromagnetic field to preheat the casting mold and the wire mesh preform to 200-300°C, and then pour the molten metal liquid of the piston base into the piston base obtained in step 3. In a carbon steel mold, the pouring temperature is 720-750°C, and the flow rate of molten metal is 15Kg/min;

After pouring for 5‐10 minutes, reduce the power of the electromagnetic field at a rate of 3KW/min, and stop applying the electromagnetic field until it is completely solidified;

The above-mentioned as-cast composite piston is remelted and heated to 565±5°C in a resistance furnace, and then sent into the forging mold cavity of the forging die machine for thixotropic forging to obtain a forged composite piston with a dense structure; The mold preheating temperature is 100°C, and the forging deformation speed is 5mm/s;

The parameter density of the composite piston prepared in this example is 2.2g/cm ³ , the bending strength is 110Mpa, the expansion coefficient is (7.5-8.5)× ^10-6 /°C, the friction coefficient is 0.045-0.060, and the thermal conductivity is 110-130W /mK, hardness HB>100, compared with a single aluminum alloy piston, the wear resistance is increased by more than 1.5 times, compared with a single silicon aluminum alloy piston, the wear resistance is increased by more than 1.8 times, in the range of 400-500 ° C The anti-oxidation performance in the body is increased by about 1 times. Compared with cast iron pistons, the mass is reduced by about 2/3. The antioxidant performance in the range of 400-500°C is about doubled.

The microstructure diagram of the enhanced wear-resistant zone of the as-cast composite piston prepared in this embodiment is shown in FIG. 3 . In Figure 3, a large number of gray particles in the composite zone are Al ₃ Ti, and the white particles and rod-like structures are Al ₃ Ni particles.

Example 3:

In this example, the outer diameter of the composite piston was prepared to be 70 mm, and the reinforced layer was an aluminum matrix composite material reinforced by Al ₃ Ti/Al ₃ Ni intermetallic compounds with a thickness of 1-2 mm, wherein the molar ratio of Al ₃ Ti/Al ₃ Ni The ratio is 2:1, and the chemical composition of the base material is: silicon: 7.5～.9.0, copper: ≤0.3 (impurity), magnesium: 0.35～0.55, zinc: ≤0.3 (impurity), manganese: ≤0.1 (impurity), titanium : 0.10 ~ 0.30, beryllium: 0.15 ~ 0.40, the rest is aluminum.

This example differs from Example 1 in that: (1) the ratio of the reinforcement Al ₃ Ti/Al ₃ Ni is different; (2) the chemical composition of the matrix is different, mainly referring to the content of silicon; (3) the thickness of the reinforcement different.

First weave the titanium-nickel alloy wire with a Ti/Ni content atomic ratio of 2:1 and a diameter of 100 μm into a mesh with a mesh size of 100 mesh, and then cut two sheets with a diameter of about The 120mm titanium-nickel alloy wire mesh sheet is overlapped to make a drum-shaped wire mesh prefabricated body, and the size of the drum is Ф70mm×50mm;

Three minutes before pouring, apply an electromagnetic field with a frequency of 2000Hz and a power of 20KW, use the electromagnetic field to preheat the piston mold and the wire mesh preform to 200-300°C, and then pour the molten metal liquid of the piston base into the piston obtained in step 3 In a low-carbon steel mold, the pouring temperature is 720-750°C, and the flow rate of molten metal is 5Kg/min;

The as-cast composite piston is remelted and heated to 560±5°C in a resistance furnace, and then sent into the forging mold cavity of the forging die machine for thixotropic forging to obtain a forged composite piston with a dense structure. The heating temperature is 300°C, and the forging deformation speed is 5mm/s;

The parameter density of the composite piston prepared in this example is 1.9g/cm ³ , the bending strength is 97Mpa, the expansion coefficient is (6.7-7.9)× ^10-6 /°C, the friction coefficient is 0.040-0.065, and the thermal conductivity is 110-130W /mK, the hardness is HB>100, compared with a single silicon-aluminum alloy piston, the wear resistance is increased by more than 1.6 times, and the oxidation resistance in the range of 400-500 ° C is increased by about 1 times, compared with cast iron pistons The weight is reduced by about 2/3, and the antioxidant performance in the range of 400-500 ° C is increased by about 1 times.

The microstructure diagram of the enhanced wear-resistant zone of the as-cast composite piston prepared in this embodiment is shown in FIG. 4 . A large number of gray particles in the composite area in Figure 4 are Al ₃ Ti; white particles and rod-like structures are Al ₃ Ni particles.

Claims (6)

1.Al ₃ti/Al ₃ni particle is collaborative strengthens sial base composite piston, and this composite piston comprises piston only and is located at the enhancing wearing layer in piston only end and circular groove region surface, and the material of described piston only is silico-aluminum, it is characterized in that,

The material of described enhancing wearing layer is Al ₃ti particle, Al ₃ni particle, Al ₃ti particle and Al ₃the intergranular silico-aluminum of Ni, described enhancing wearing layer is (1 ~ 10) by the mol ratio of Ti and Ni: prepared by the Ti-Ni alloy silk of (1 ~ 10), the diameter of described Ti-Ni alloy silk is 50 ~ 150 μm.

2. Al as claimed in claim 1 ₃ti/Al ₃ni particle is collaborative strengthens sial base composite piston, and it is characterized in that, the thickness of described enhancing wearing layer is 1 ~ 5mm.

3. the Al described in claim 1 or 2 ₃ti/Al ₃ni particle works in coordination with the preparation method strengthening sial base composite piston, and it is characterized in that, the method comprises the following steps:

Arrange graphite paper at Piston mould inwall, graphite paper is placed Ti-Ni alloy silk screen, afterwards, under electromagnetic field environment, in Piston mould, pours into a mould silumin alloy melt, after silico-aluminum solidifies, stop applying electromagnetic field, obtain semi-finished product; And when silico-aluminum starts to solidify, reduce the intensity of electromagnetic field, and reduce the power of electromagnetic field gradually in silico-aluminum process of setting, when silico-aluminum solidifies completely, the power of electromagnetic field reduces to zero;

Semi-finished product are forged, heat treatment, machining and grinding process;

Finished product is obtained after above-mentioned steps.

4. Al as claimed in claim 3 ₃ti/Al ₃ni particle works in coordination with the preparation method strengthening sial base composite piston, and it is characterized in that, described Ti-Ni alloy silk screen is 20 ~ 100 object Ti-Ni alloy silk screens.

5. Al as claimed in claim 3 ₃ti/Al ₃ni particle works in coordination with the preparation method strengthening sial base composite piston, it is characterized in that, the frequency of described electromagnetic field is 2000 ~ 3000Hz, power is 20 ~ 30KW.

6. Al as claimed in claim 3 ₃ti/Al ₃ni particle works in coordination with the preparation method strengthening sial base composite piston, and it is characterized in that, the method comprises the following steps:

(1) arrange one deck graphite paper at Piston mould inwall, then Ti-Ni alloy silk screen is close to graphite paper layout;

(2) start to apply that frequency is 2000 ~ 3000Hz, power is the electromagnetic field of 20 ~ 30KW before cast, first Piston mould and Ti-Ni alloy silk screen are preheating to 200 ~ 300 DEG C;

Then be cast in Piston mould by the silumin alloy melt of melting, pouring temperature is 700 ~ 760 DEG C, and silumin alloy melt flow is 5 ~ 15Kg/min;

After pouring 5 ~ 10min, by the rate reduction electromagnetic field power of 3 ~ 5KW/min, after silico-aluminum solidifies completely, stop applying electromagnetic field, state composite piston must be cast;

(3) state composite piston remelting to 550 DEG C ~ 570 DEG C will be cast, then send in the forging die cavity of forging die machine, carry out thixotroping forging and stamping process, obtain forging state composite piston, during forging, in model cavity, preheating temperature is: 100 ~ 300 DEG C, and forging deformation speed is 5 ~ 15mm/s;

(4) state composite piston will be forged under 450 ~ 500 DEG C of conditions, process 8 ~ 10h, then under 150 ~ 200 DEG C of conditions, process 3 ~ 6h;

Machining and polishing are carried out to the piston after step (4) process, obtains Al ₃ti/Al ₃ni two kinds of particles work in coordination with the sial base composite piston of enhancing.