CN102978498A - Rare-earth magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention relates to a rare-earth magnesium alloy and a preparation method thereof. The technical problem that the rare-earth magnesium alloy in the prior art cannot meet the requirement for industrialization is solved. The rare-earth magnesium alloy comprises the following main components in percentage by weight: 1.0 to 4.0 percent of Zn, 0.1 to 0.5 percent of Ca, 0.1 to 1.0 percent of La, 0.3 to 3.0 percent of Ce, and the balance of Mg. The heat-resistant temperature, the strength and the like of the rare-earth magnesium alloy are higher than those of the conventional magnesium alloy. The invention also provides the preparation method for the rare-earth magnesium alloy. The prepared alloy has the advantages of high strength, high toughness, low cost, good heat resistance and corrosion resistance and the like through component design of the Mg-Zn-Ca-La/Ce alloy and selection of the raw materials by combining casting, hot extrusion technology and post ageing treatment.

Description

A kind of rare earth magnesium alloy and preparation method thereof

technical field

The invention relates to the technical field of magnesium alloys, in particular to a low-cost and high-performance Mg-Zn-Ca-La/Ce alloy and a preparation method thereof.

Background technique

Magnesium alloy has high specific strength, specific stiffness, good damping, machinability and thermal conductivity, strong electromagnetic shielding ability, easy recycling, regeneration and many other excellent properties, making it widely used in aerospace, automobile industry, electronics industry The application in the fields of national economy and national defense is expanding day by day. And magnesium is the lightest metal structure material, the density is only 1.74g/cm ³ , which is 2/3 of aluminum and 1/4 of steel. The wide application of magnesium alloy in industry will have a positive effect on energy saving and emission reduction . Therefore, magnesium alloy is known as "the green engineering material of the 21st century".

Traditional magnesium alloys such as Mg–Al–Zn and Mg–Al–Mn have been widely used and are still the most widely used magnesium alloys. The outstanding feature of this type of magnesium alloy is its excellent die-casting process performance, which is one of the main reasons for their wide application. However, these alloys all have a common disadvantage, that is, when used above 120oC, the mechanical properties of the alloy decrease significantly due to the softening of the β phase (Mg17Al12). Therefore, people improve the mechanical properties of magnesium alloys by adding appropriate alloying elements to form second phase particles with high thermal stability in magnesium alloys. Rare earth (RE) elements are widely used as alloying elements due to their unique electron configuration outside the nucleus. It has been found that the addition of rare earth elements can greatly improve the high temperature tensile properties, creep properties, corrosion resistance and heat resistance of magnesium alloys. However, the mechanical properties of existing magnesium alloys cannot meet the needs of industrialization, and the preparation cost of rare earth magnesium alloys with higher performance is relatively high, which limits their application in industrial production. Only rare earth magnesium alloys with excellent mechanical properties and high cost performance will have broad application prospects.

Contents of the invention

The invention provides a high-performance, low-cost rare-earth magnesium alloy and a preparation method thereof to solve the technical problem that the rare-earth magnesium alloy in the prior art cannot meet the requirements of industrialization.

In order to solve the problems of the technologies described above, the technical solution of the present invention is specifically as follows:

A rare-earth magnesium alloy, the main components of the rare-earth magnesium alloy and their weight percentages are: Zn is 1.0-4.0%, Ca is 0.1-0.5%, La is 0.1-1.0%, Ce is 0.3-3.0%, and the balance is Mg.

A preparation method of a rare earth magnesium alloy, the preparation method comprising the following process steps:

(1) According to the weight ratio: Zn is 1.0~4.0%, Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance is Mg, and the casting of Mg–Zn–Ca–La is carried out /Ce alloy;

(2) Homogenize the as-cast Mg–Zn–Ca–La/Ce alloy;

(3) Turn the homogenized Mg–Zn–Ca–La/Ce alloy into an extrusion ingot of Φ80×200mm, and then hot-extrude the alloy;

(4) The hot-extruded Mg–Zn–Ca–La/Ce alloy was subjected to aging treatment.

In the preparation method of the rare earth magnesium alloy provided by the present invention, the specific process steps of the step (1) are as follows:

a. According to the weight ratio: Zn is 1.0~4.0%, Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance is Mg, and the material is prepared;

b. Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, dry it, then put it into the crucible in the well-type resistance furnace, pass it into the mixed protective gas of CO ₂ +SF ₆ (40:1), and heat it to 740 ~ 760oC; after the alloy is melted, preheat pure Zn particles, La/Ce metal or Mg–La/Ce master alloy, the preheating temperature is 200~300oC, then add pure Ca particles or Mg-Ca master alloy, and Introduce Ar gas into the crucible to prevent combustion, the flow rate is 1nL/min, and the time is 1 minute. After stirring and standing for 10 minutes, cool down to 710~730oC and cast it into a mold to obtain Mg–Zn–Ca–La/Ce alloy.

In the preparation method of the rare earth magnesium alloy provided by the present invention, the specific process steps of the step (2) are as follows:

Homogenize the as-cast Mg–Zn–Ca–La/Ce alloy at a temperature of 300–450oC, a heating rate of 4oC/min, a holding time of 8–64h, and then water quenching at 60–80oC.

In the preparation method of the rare earth magnesium alloy provided by the present invention, the specific process steps of the step (3) are as follows:

Turn the homogenized alloy into an extruded ingot of Φ80×200mm, and preheat it at 250~400oC for 20 minutes, then use a horizontal extruder to hot extrude the alloy at 250~400oC , the extrusion ratio is 18:1, the moving speed of the extrusion head is 1.0~20.0mm/s, and the exit of the mold adopts 50oC water-cooled extrusion rod.

In the preparation method of the rare earth magnesium alloy provided by the present invention, the specific process steps of the step (4) are as follows:

The hot-extruded Mg–Zn–Ca–La/Ce alloy is subjected to aging treatment, the aging temperature is 150~250oC, the holding time is 8h~120h, and then 25oC water cooling.

Technical effect of the present invention is:

The rare earth magnesium alloy provided by the invention is obtained by adding a certain amount of low-cost lanthanum/cerium (La/Ce) mixed rare earth, zinc and calcium elements after extracting praseodymium (Pr) and neodymium (Nd) into pure magnesium, through casting, A low-cost and high-strength heat-resistant rare earth magnesium alloy is prepared by homogenization treatment and hot extrusion deformation technology. In this alloy, magnesium, zinc, calcium and rare earth elements can form intermetallic compounds with good thermal stability, which can increase the heat resistance temperature of magnesium alloys to 200~300oC, and at the same time, the microalloying of La/Ce mixed rare earths can also be significantly improved. The microstructure of magnesium alloy greatly improves the hot deformation processing ability of the alloy, which is beneficial to the industrial production of the alloy. In addition, the invention finds a suitable application field for a large backlog of lanthanum/cerium mixed rare earths, which helps to alleviate the imbalance between the production and sales of light rare earth resources in my country.

The addition of the rare earth element La/Ce in the alloy of the present invention also improves the strength of the alloy, and its strength exceeds 350 MPa, while the strength of the current deformed Mg-Zn-Ca alloy is generally lower than 330 MPa;

The heat-resistant temperature of the alloy of the invention can reach 200-300°C, and compared with the existing Mg-Zn-Ca alloy (heat-resistant temperature of 200°C), its heat-resistant performance is also improved.

The preparation method of the rare earth magnesium alloy provided by the present invention, the main steps are: the composition design of Mg-Zn-Ca-La/Ce alloy and the selection of raw materials, the composition and mass percentage are: Zn is 1.0~4.0% , Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance is Mg. According to the designed components and their mass percentages, the raw casting alloy is added, combined with hot extrusion technology and post-aging treatment, the prepared alloy has the advantages of high strength, high toughness, low cost, good heat resistance and corrosion resistance.

Detailed ways

The specific embodiment of the present invention is:

The preparation method of the rare earth magnesium alloy provided by the invention is specifically as follows:

(1) The present invention uses commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Ca with a purity of 99.50 wt.%, La/Ce metal or Mg–La/Ce master alloy (the composition is Mg –15 wt.% Ce–5 wt.% La) as raw material; according to the weight ratio: Zn is 1.0~4.0%, Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance Prepare materials for Mg; among them, pure Ca grains can be replaced by Mg-Ca master alloy;

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, dry it, put it into a crucible in a well-type resistance furnace, pass it into a mixed protective gas of CO ₂ +SF ₆ (40:1), and heat it to 740 ~ 760oC; After the alloy is melted, add pure Zn grains and Mg–La/Ce master alloy (preheating temperature is 200~300oC), then add pure Ca grains, and pass Ar gas into the crucible to prevent combustion, the flow rate is 1nL /min, the time is 1 minute, after stirring and standing for 10 minutes, the temperature is lowered to 710~730oC and cast into a 45# steel permanent cylindrical mold to obtain a Mg–Zn–Ca–La/Ce alloy;

(2) Homogenize the as-cast Mg–Zn–Ca–La/Ce alloy at a temperature of 300~450oC, a heating rate of 4oC/min, a holding time of 8~64h, and then water quenching at 60~80oC;

(3) Turn the homogenized alloy into an extruded ingot of Φ80×200mm, and preheat it at 250~400oC for 20 minutes, then use a horizontal extruder to hot extrude the alloy at 250 ~400oC, the extrusion ratio is 18:1, the moving speed of the extrusion head is 1.0~20.0mm/s, and the exit of the mold is 50oC water-cooled extrusion rod (to prevent grain growth);

(4) The hot-extruded alloy is subjected to aging treatment in a heat treatment furnace, the aging temperature is 150~250oC, the holding time is 8h~120h, and then 25oC water cooling.

Example 1

(1) Commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Ca with a purity of 99.50 wt.%, Mg–La/Ce master alloy (composition of Mg–15 wt.%Ce–5 wt.% La) is the raw material, according to the mass percentage: Zn is 1.0%, Ca is 0.1%, La is 0.1%, Ce is 0.3%, and the balance is Mg for material preparation.

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, blow dry, then put it into the crucible in the well-type resistance furnace, pass through the mixed protective gas of CO ₂ +SF ₆ (40:1), and heat to 740oC. After the alloy is melted, preheat the pure Zn particles and the Mg–La/Ce master alloy at a temperature of 200oC, then add pure Ca particles, and pass Ar gas into the crucible to prevent combustion, with a flow rate of 1nL/min. The time is 1 minute, after stirring and standing for 10 minutes, the temperature is lowered to 710oC and cast into a 45# steel permanent cylindrical mold to obtain a Mg–Zn–Ca–La/Ce alloy.

(2) Put the as-cast Mg–Zn–Ca–La/Ce alloy into a box-type heat treatment furnace, heat up to the homogenization target temperature of 300oC, the heating rate is 4oC/min, the holding time is 8h, and then quenched in water at 60oC.

(3) The homogenized alloy is processed into an extrusion ingot of Φ80×200mm, and after preheating at 250oC for 20 minutes, the alloy is hot-extruded with a horizontal extruder at a temperature of 250oC. The pressure ratio is 18:1, the moving speed of the extrusion head is 1.0mm/s, and a 50oC water-cooled extrusion rod is used at the exit of the die.

(4) The alloy after hot extrusion deformation is subjected to aging treatment in a heat treatment furnace, the aging temperature is 150oC, the holding time is 120h, and then 25oC water cooling.

Example 2

(1) Commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Mg–30 wt.% Ca master alloy, Mg–La/Ce master alloy (composition is Mg–15 wt.% Ce– 5 wt.% La) as the raw material, according to the mass percentage: Zn is 1.0%, Ca is 0.1%, La is 0.1%, Ce is 0.3%, and the balance is Mg for material preparation.

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, blow dry, then put it into the crucible in the well-type resistance furnace, pass through the mixed protective gas of CO ₂ +SF ₆ (40:1), and heat to 740oC. After the alloy is melted, preheat the pure Zn particles and the Mg–La/Ce master alloy at 200oC, then add the Mg–Ca master alloy, stir and stand for 10 minutes, then cool down to 710oC and cast into 45# steel In the permanent cylindrical mold, the Mg–Zn–Ca–La/Ce alloy was obtained.

(2) The as-cast Mg–Zn–Ca–La/Ce alloy was placed in a box-type heat treatment furnace, heated to the homogenization target temperature of 300oC, the heating rate was 4oC/min, the holding time was 8h, and then water quenched at 60oC.

(3) The homogenized alloy is processed into an extrusion ingot of Φ80×200mm, and after preheating at 250oC for 20 minutes, the alloy is hot-extruded with a horizontal extruder at a temperature of 250oC. The pressure ratio is 18:1, the moving speed of the extrusion head is 1.0mm/s, and a 50oC water-cooled extrusion rod is used at the exit of the die.

(4) The alloy after hot extrusion deformation is subjected to aging treatment in a heat treatment furnace, the aging temperature is 150oC, the holding time is 120h, and then 25oC water cooling.

Example 3

(1) Commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Mg–30 wt.% Ca master alloy, and La/Ce metal with a purity of 99.50 wt.% are raw materials, according to mass percentage : Zn is 1.0%, Ca is 0.1%, La is 0.1%, Ce is 0.3%, and the balance is Mg for material preparation.

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, blow dry, then put it into the crucible in the well-type resistance furnace, pass through the mixed protective gas of CO ₂ +SF ₆ (40:1), and heat to 740oC. After the alloy is melted, preheat the pure Zn particles and La/Ce metal at 200oC, then add the Mg–Ca master alloy, stir and stand for 10 minutes, then cool down to 710oC and cast into 45# steel permanent type In a cylindrical mold, a Mg–Zn–Ca–La/Ce alloy was obtained.

(2) Put the as-cast Mg–Zn–Ca–La/Ce alloy into a box-type heat treatment furnace, heat up to the homogenization target temperature of 300oC, the heating rate is 4oC/min, the holding time is 8h, and then quenched in water at 60oC.

(3) The homogenized alloy is processed into an extrusion ingot of Φ80×200mm, and after preheating at 250oC for 20 minutes, the alloy is hot-extruded with a horizontal extruder at a temperature of 250oC. The pressure ratio is 18:1, the moving speed of the extrusion head is 1.0mm/s, and a 50oC water-cooled extrusion rod is used at the exit of the die.

(4) The alloy after hot extrusion deformation is subjected to aging treatment in a heat treatment furnace, the aging temperature is 150oC, the holding time is 120h, and then 25oC water cooling.

Example 4

(1) Commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Ca with a purity of 99.50 wt.%, Mg–La/Ce master alloy (composition of Mg–15 wt.%Ce–5 wt.% La) is the raw material, according to the mass percentage: Zn is 2.0%, Ca is 0.3%, La is 0.5%, Ce is 1.5%, and the balance is Mg for material preparation.

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, blow dry, then put it into a crucible in a well-type resistance furnace, pass in a mixed protective gas of CO ₂ +SF ₆ (40:1), and heat to 750oC. After the alloy is melted, preheat the pure Zn particles and the Mg–La/Ce master alloy at a temperature of 250oC, then add pure Ca particles, and pass Ar gas into the crucible to prevent combustion, with a flow rate of 1nL/min. The time is 1 minute. After stirring and standing for 10 minutes, the temperature is lowered to 720oC and cast into a 45# steel permanent cylindrical mold to obtain a Mg–Zn–Ca–La/Ce alloy.

(2) Put the as-cast Mg–Zn–Ca–La/Ce alloy into a box-type heat treatment furnace, heat up to the homogenization target temperature of 350oC, the heating rate is 4oC/min, the holding time is 32h, and then quenched in water at 70oC.

(3) Process the homogenized alloy into an extruded ingot of Φ80×200mm, and after preheating at 300oC for 20 minutes, use a horizontal extruder to hot-extrude the alloy. The extrusion temperature is 300oC. The pressure ratio is 18:1, the moving speed of the extrusion head is 5.0mm/s, and a 50oC water-cooled extrusion rod is used at the exit of the die.

(4) The alloy after hot extrusion deformation is subjected to aging treatment in a heat treatment furnace, the aging temperature is 180oC, the holding time is 64h, and then 25oC water cooling.

Example 5

(1) Commercial high-purity magnesium with a purity of 99.90 wt.%, Zn particles with a purity of 99.90 wt.%, Ca with a purity of 99.50 wt.%, Mg–La/Ce master alloy (composition of Mg–15 wt.%Ce–5 wt.% La) is the raw material, according to the mass percentage: Zn is 4.0%, Ca is 0.5%, La is 1.0%, Ce is 3.0%, and the balance is Mg for material preparation.

Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, blow dry, then put it into a crucible in a well-type resistance furnace, pass in a mixed protective gas of CO ₂ +SF ₆ (40:1), and heat it to 760oC. After the alloy is melted, preheat the pure Zn grains and the Mg–La/Ce master alloy at a temperature of 300oC, then add pure Ca grains, and pass Ar gas into the crucible to prevent combustion, with a flow rate of 1nL/min. The time is 1 minute, after stirring and standing for 10 minutes, the temperature is lowered to 730oC and cast into a 45# steel permanent cylindrical mold to obtain a Mg–Zn–Ca–La/Ce alloy.

(2) Put the as-cast Mg–Zn–Ca–La/Ce alloy into a box-type heat treatment furnace, heat up to the homogenization target temperature of 450oC, the heating rate is 4oC/min, the holding time is 64h, and then 80oC water quenching.

(3) The homogenized alloy is processed into an extrusion ingot of Φ80×200mm, and after preheating at 400oC for 20 minutes, the alloy is hot-extruded by a horizontal extruder at a temperature of 400oC. The pressure ratio is 18:1, the moving speed of the extrusion head is 20.0mm/s, and a 50oC water-cooled extrusion rod is used at the exit of the die.

(4) The alloy after hot extrusion deformation is subjected to aging treatment in a heat treatment furnace, the aging temperature is 250oC, the holding time is 8h, and then 25oC water cooling.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (6)

1. A rare earth magnesium alloy, characterized in that, the main components and weight percentages of the rare earth magnesium alloy are: Zn is 1.0 ~ 4.0%, Ca is 0.1 ~ 0.5%, La is 0.1 ~ 1.0%, and Ce is 0.3 ~ 3.0%, the balance is Mg. 2. the preparation method of rare earth magnesium alloy as claimed in claim 1 is characterized in that, this preparation method comprises the following processing steps: (1) According to the weight ratio: Zn is 1.0~4.0%, Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance is Mg, and the casting of Mg–Zn–Ca–La is carried out /Ce alloy; (2) Homogenize the as-cast Mg–Zn–Ca–La/Ce alloy; (3) Turn the homogenized Mg–Zn–Ca–La/Ce alloy into an extrusion ingot of Φ80×200mm, and then hot-extrude the alloy; (4) The hot-extruded Mg–Zn–Ca–La/Ce alloy was subjected to aging treatment. 3. The preparation method of rare earth magnesium alloy as claimed in claim 2, characterized in that, the specific process steps of the step (1) are as follows: a. According to the weight ratio: Zn is 1.0~4.0%, Ca is 0.1~0.5%, La is 0.1~1.0%, Ce is 0.3~3.0%, and the balance is Mg, and the material is prepared; b. Clean the surface of the pure magnesium ingot with alcohol, rinse it with cold water, dry it, then put it into the crucible in the well-type resistance furnace, pass it into the mixed protective gas of CO ₂ +SF ₆ (40:1), and heat it to 740 ~ 760oC; after the alloy is melted, preheat pure Zn particles, La/Ce metal or Mg–La/Ce master alloy, the preheating temperature is 200~300oC, then add pure Ca particles or Mg-Ca master alloy, and Introduce Ar gas into the crucible to prevent combustion, the flow rate is 1nL/min, and the time is 1 minute. After stirring and standing for 10 minutes, cool down to 710~730oC and cast it into a mold to obtain Mg–Zn–Ca–La/Ce alloy. 4. The preparation method of rare earth magnesium alloy as claimed in claim 2, characterized in that, the specific process steps of the step (2) are as follows: Homogenize the as-cast Mg–Zn–Ca–La/Ce alloy at a temperature of 300–450oC, a heating rate of 4oC/min, a holding time of 8–64h, and then water quenching at 60–80oC. 5. The preparation method of rare earth magnesium alloy as claimed in claim 2, characterized in that, the specific process steps of the step (3) are as follows: Turn the homogenized alloy into an extruded ingot of Φ80×200mm, and preheat it at 250~400oC for 20 minutes, then use a horizontal extruder to hot extrude the alloy at 250~400oC , the extrusion ratio is 18:1, the moving speed of the extrusion head is 1.0~20.0mm/s, and the exit of the mold adopts 50oC water-cooled extrusion rod. 6. The preparation method of rare earth magnesium alloy according to claim 2, characterized in that, the specific process steps of the step (4) are as follows: The hot-extruded Mg–Zn–Ca–La/Ce alloy is subjected to aging treatment, the aging temperature is 150~250oC, the holding time is 8h~120h, and then 25oC water cooling.