CN103305738A - Silicon-containing heat-resistant rare earth magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a silicon-containing heat-resistant rare earth magnesium alloy and a preparation method thereof; the alloy comprises the following components in weight percent: Gd5-10%, Y2-8%, Si0.3-2%, Zr0.35 ～0.8%, Gd+Y11～13%, impurity is less than 0.02%, and the balance is magnesium; the present invention also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy, the method comprising: raw material preheating, smelting and subsequent Heat treatment; the smelting is carried out under the protection of a flux or a mixed gas of SF ₆ and CO ₂ ; the subsequent heat treatment is to perform solution treatment and aging treatment on the silicon-containing heat-resistant rare earth magnesium alloy. The invention has a simple process, low rare earth content, and ensures excellent plasticity while increasing the strength of the alloy. By adjusting the alloy composition and heat treatment process, a high-strength, high-toughness, heat-resistant and wear-resistant magnesium alloy can be obtained, which can be applied to automotive, aerospace, military, etc. Multi-field, to meet the needs of a variety of applications.

Description

Silicon-containing heat-resistant rare earth magnesium alloy and preparation method thereof

technical field

The invention relates to a magnesium alloy in the field of metal structural materials and a preparation method thereof, in particular to a silicon-containing heat-resistant rare earth magnesium alloy and a preparation method thereof.

Background technique

Magnesium alloy is the lightest metal structure material currently used. It has high specific strength, specific stiffness, good thermal conductivity, electrical conductivity and electromagnetic shielding performance. It has a wide range of applications in the fields of automobiles, electronics, home appliances, communications, instruments, and aerospace. prospect. In particular, it can meet the requirements of the automotive industry in terms of light weight, low energy consumption, and high environmental protection, so it has received extensive attention. However, the defects of low strength and poor plasticity of common magnesium alloys at high temperature restrict their application in engine and power system parts. Therefore, improving the mechanical properties of magnesium alloys, including high temperature strength, plasticity, creep resistance and wear resistance, is the basis for expanding its industrial applications. Therefore, it is necessary to develop high-performance heat-resistant magnesium alloys. In recent years, studies have found that the addition of rare earth elements can greatly improve the high-temperature performance and creep resistance of the alloy, so a series of heat-resistant magnesium alloys that can be used for a long time at 200-250 ° C have been developed, such as Mg-Y -RE series alloys WE54 and WE43 alloys, which have been commercialized. After the as-cast WE54 alloy is treated with T6, the tensile strength at room temperature is 280MPa, the yield strength is 172MPa, and the elongation is 2%; the tensile strength is 240MPa, the yield strength is 150MPa, and the elongation is 7% at 200°C; 200°C/80MPa The creep deformation is 0.1% in 100h.

According to the literature search of the prior art, it is found that Gd and Y elements have good solid solution strengthening and aging strengthening effects in magnesium alloys, and can significantly improve the performance of magnesium alloys, thereby obtaining Mg-Gd-Y alloys. In the patent literature, Chinese Patent, whose publication number is CN1804083A, a kind of high-strength heat-resistant rare earth magnesium alloy is recorded, its composition and weight percentage are: Gd2～10%, Y3～12%, the weight sum of Gd and Y is 13-14%, Zr0.3-0.7% and not more than 0.3% of active elements (any one of Zn, Ag, Cu, Sr, Sr, Ca, Ti, Bi, Cd), or 0.6-1.5% of Mn And not more than 0.3% of the activation element (Sn, Si, Sb, Ca any one), the rest is magnesium. This rare earth magnesium alloy forms a network phase structure through precipitates, has high strength and creep resistance, and the ultimate tensile strength is 180MPa at 300°C. However, the rare earth content in this patent is relatively high and not optimized. On the one hand, it brings about an increase in cost; , Si element is only added together with Mn in a very small amount, not as a special strengthening element. Combined with the current patent about Si-containing Mg-Al-Si and Mg-Al-Si-RE (such as Chinese patent, its publication number is CN1796024A) and Mg-Zn-Si-RE alloys (such as Chinese patent: The application number is 200410102511, the publication number is CN1886528A and the publication number is CN101027420A) has good heat resistance and wear resistance. The present invention aims to synthesize the comprehensive excellent properties of magnesium alloys containing Si and rare earth elements, and optimize the reasonable RE content and subsequent heat treatment process, a high-performance magnesium alloy with high strength, high toughness, heat resistance and wear resistance is obtained.

Contents of the invention

Aiming at the defects in the prior art, the object of the present invention is to provide a silicon-containing heat-resistant rare earth magnesium alloy and a preparation method thereof. By adding Gd, Y, Zr and a small amount of Si elements to Mg, and optimizing the solid solution and aging process parameters, under a reasonable total amount of rare earth elements, excellent room temperature and high temperature strength and plasticity can be obtained, and the alloy can be maintained. Improve the wear resistance of the alloy while improving the heat resistance, and obtain a heat-resistant magnesium alloy with excellent comprehensive properties.

The present invention is achieved through the following technical solutions:

In the first aspect, the present invention relates to a heat-resistant rare earth magnesium alloy containing silicon, said alloy comprising the following components in weight percentage:

Gd 5～10%,

Y 2～8%,

Si 0.3～2%,

Zr 0.35～0.8%,

Gd+Y 11～13%,

Impurities are less than 0.02%,

The balance is magnesium.

Preferably, the weight percentage of each component of the impurities is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

In the second aspect, the present invention also relates to a method for preparing the aforementioned silicon-containing heat-resistant rare earth magnesium alloy, the method comprising: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheating raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy;

Step 2, smelting: the smelting is carried out under the protection of flux or SF ₆ and CO ₂ mixed gas, including the following steps:

Step 2.1, heating and melting the magnesium ingot;

Step 2.2, after the magnesium ingot is completely melted, add Mg-Si master alloy and stir, then add Mg-Gd master alloy, Mg-Y master alloy, Mg-Zr master alloy in turn, keep warm, add refining agent to refine, let stand, Slag removal, ladle casting or low pressure casting to obtain silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment includes the following steps:

The heat-resistant rare earth magnesium alloy containing silicon is subjected to solution treatment and aging treatment.

Preferably, in step 1, the preheating temperature is 180-220°C.

Preferably, in step 2.2, the Mg-Si master alloy is added when the temperature of the magnesium liquid is 660-680°C, and the stirring time is 3-5 minutes; the Mg-Gd master alloy is added when the temperature of the magnesium liquid is 730-750°C, and the After the temperature of the magnesium liquid rises to 730-750°C and stabilizes, add the Mg-Y alloy. When the temperature of the magnesium liquid is 780-790°C, add the Mg-Zr master alloy. The holding temperature is 780°C and the holding time is 5-15 minutes.

Preferably, in step 2.2, the refining time is 5-15 minutes, the standing temperature is 760-780°C, the standing time is 20-30 minutes, and the slag removal temperature is 700-720°C.

Preferably, in the step 3, the temperature of the solution treatment is 480-520° C., and the time is 4-20 hours; the temperature of the aging treatment is 200-250° C., and the time is 8-50 hours.

Preferably, the mass fraction of magnesium in the magnesium ingot is >99.9%, and the flux and refining agent are magnesium alloy fluxes containing MgCl ₂ , KCl, and CaF ₂ .

Preferably, the volume percentage of SF ₆ in the mixed gas of SF ₆ and CO ₂ is 0.2%.

Preferably, the refining process is accompanied by stirring.

The present invention has following beneficial effects:

(1) The alloy of the present invention adds a small amount of Si and further optimizes the content of Gd and Y, so that the alloy has higher strength and good plasticity; on the premise of ensuring sufficient strengthening effect, the total amount of rare earth elements is controlled, and the added Si forms Mg ₂ Si and (RE _x Si _y ) hard phase, which has a high melting point and high specific stiffness, which can effectively improve the wear resistance of the alloy; adding Zr can significantly refine the grains through heterogeneous nucleation, and enhance fine-grain strengthening effect and improve alloy plasticity;

(2) The present invention combines optimization of solid solution and aging process parameters to increase and refine the number of aging precipitated phases. Through the above principles and methods, the alloy of the present invention has excellent properties such as low rare earth content, high strength, good plasticity, heat resistance and wear resistance.

(3) The invention has a simple process and low rare earth content, which ensures excellent plasticity while increasing the strength of the alloy, and can obtain high-strength, high-toughness, heat-resistant and wear-resistant magnesium with different excellent performance combinations by adjusting the alloy composition and heat treatment process alloy. It is suitable for large-scale production and can be used in many fields such as automobile, aerospace and military industry to meet the needs of various application occasions.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1

This embodiment relates to a silicon-containing heat-resistant rare earth magnesium alloy, which contains the following components by weight percentage:

9%Gd, 2%Y, 0.5%Si and 0.35%Zr, the rest is Mg and unavoidable impurities (less than 0.02% by weight). Among them, the content of impurity elements is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

This embodiment also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy. The method includes: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheating the raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy to 200°C;

Step 2, smelting: under the protection of SF ₆ and CO ₂ mixed gas (SF ₆ volume percentage is 0.2%), including the following steps: (1) Adding magnesium: adding pure magnesium to a resistance crucible furnace for smelting; (2 ) Add Si: After the magnesium is completely melted, add the Mg-Si master alloy at 680°C and stir for 5 minutes; (3) Add Gd and Y: Add the Mg-Gd master alloy after the temperature rises to 730°C, and wait for the temperature of the magnesium liquid to rise Add Mg-Y master alloy at 730°C; (4) Add Zr: increase the temperature of magnesium liquid to 780°C and add Mg-Zr master alloy; Minutes, the refining process needs to be fully stirred; (6) Casting: After refining, stand at 760°C for 30 minutes, wait for the magnesium liquid to cool to 700°C to skim off the scum, cast with a metal mold, and preheat the steel mold for casting to 250°C , and then get silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment: at a temperature of 500° C., solution treatment for 6 hours, and then at a temperature of 250° C., for 8 hours of aging treatment.

Implementation effect: the silicon-containing heat-resistant rare earth magnesium alloy prepared in this example has a tensile strength of 330MPa at room temperature, a yield strength of 210MPa, and an elongation of 10%; a tensile strength of 310MPa at 200°C, a yield strength of 190MPa, and an elongation of 16%; Under the condition of 80MPa, the creep deformation after 100 hours is 0.065%.

Example 2

This embodiment relates to a silicon-containing heat-resistant rare earth magnesium alloy, which contains the following components by weight percentage: 8% Gd, 3% Y, 1% Si and 0.6% Zr, and the rest is Mg and unavoidable impurities (weight percentage is less than 0.02%), wherein the content of impurity elements is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

This embodiment also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy. The method includes: the method includes: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheat raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy to 220°C;

Step 2, smelting: under the protection of SF ₆ and CO ₂ mixed gas (SF ₆ volume percentage is 0.2%), including the following steps: (1) Adding magnesium: adding pure magnesium to a resistance crucible furnace for smelting; (2 ) Add Si: After the magnesium is completely melted, add the Mg-Si master alloy at 660°C and stir for 4 minutes; (3) Add Gd and Y: Add the Mg-Gd master alloy after the temperature rises to 740°C, and wait for the temperature of the magnesium liquid to rise Add Mg-Y master alloy when it reaches 740°C; (4) Add Zr: raise the temperature of magnesium liquid to 790°C and add Mg-Zr master alloy; Minutes, the refining process needs to be fully stirred; (6) Casting: After refining, stand at 770°C for 25 minutes, wait for the magnesium liquid to cool to 710°C to skim off the scum, cast with a metal mold, and preheat the steel mold for casting to 240°C , and then get silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment: at a temperature of 500° C., solution treatment for 8 hours, and then at a temperature of 225° C., for 16 hours of aging treatment.

Implementation effect: the silicon-containing heat-resistant rare earth magnesium alloy prepared in this example has a tensile strength of 350MPa at room temperature, a yield strength of 220MPa, and an elongation of 8%; a tensile strength of 320MPa at 200°C, a yield strength of 205MPa, and an elongation of 14%; Under the condition of 80MPa, the creep deformation after 100 hours is 0.052%.

Example 3

This embodiment relates to a silicon-containing heat-resistant rare earth magnesium alloy, which contains the following components by weight percentage: 10% Gd, 3% Y, 2% Si and 0.5% Zr, and the rest is Mg and unavoidable impurities (weight percentage is less than 0.02%), wherein the content of impurity elements is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

This embodiment also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy. The method includes: the method includes: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheat raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy to 210°C;

Step 2, smelting: under the protection of SF ₆ and CO ₂ mixed gas (SF ₆ volume percentage is 0.2%), including the following steps: (1) Adding magnesium: adding pure magnesium to a resistance crucible furnace for smelting; (2 ) Add Si: After the magnesium is completely melted, add the Mg-Si master alloy at 670°C and stir for 3 minutes; (3) Add Gd and Y: Add the Mg-Gd master alloy after the temperature rises to 750°C, and wait for the temperature of the magnesium liquid to rise Add Mg-Y master alloy at 750°C; (4) Add Zr: raise the temperature of magnesium liquid to 790°C and add Mg-Zr master alloy; Minutes, the refining process needs to be fully stirred; (6) Casting: After refining, stand at 780°C for 20 minutes, wait for the magnesium liquid to cool to 720°C to skim off the scum, cast with a metal mold, and preheat the steel mold for casting to 260°C , and then get silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment: at a temperature of 490°C, perform a solution treatment for 10 hours, and then at a temperature of 200°C, perform an aging treatment for 50 hours.

Implementation effect: the silicon-containing heat-resistant rare earth magnesium alloy prepared in this example has a tensile strength of 360MPa at room temperature, a yield strength of 230MPa, and an elongation of 6%; a tensile strength of 340MPa at 200°C, a yield strength of 215MPa, and an elongation of 12%; Under the condition of 80MPa, the creep deformation after 100 hours is 0.042%.

Example 4

This embodiment relates to a silicon-containing heat-resistant rare earth magnesium alloy, which contains the following components by weight percentage: 5%Gd, 8%Y, 1.5%Si and 0.4%Zr, and the rest is Mg and unavoidable impurities , wherein the content of impurity elements is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

This embodiment also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy. The method includes: the method includes: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheating the raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy to 180°C;

Step 2, smelting: under the protection of SF ₆ and CO ₂ mixed gas (SF ₆ volume percentage is 0.2%), including the following steps: (1) Adding magnesium: adding pure magnesium to a resistance crucible furnace for smelting; (2 ) Add Si: After the magnesium is completely melted, add the Mg-Si master alloy at 670°C and stir for 4 minutes; (3) Add Gd and Y: Add the Mg-Gd master alloy after the temperature rises to 730°C, and wait for the temperature of the magnesium liquid to rise Add Mg-Y master alloy when it reaches 730°C; (4) Add Zr: raise the temperature of magnesium liquid to 785°C and add Mg-Zr master alloy; Minutes, the refining process needs to be fully stirred; (6) Casting: After refining, stand at 760 ° C for 25 minutes, wait for the magnesium liquid to cool to 700 ° C to skim off the scum, cast with a metal mold, and the steel mold for casting is preheated to 250 ° C , and then get silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment: solution treatment for 20 hours at a temperature of 480°C, and aging treatment for 50 hours at a temperature of 200°C.

Implementation effect: the silicon-containing heat-resistant rare earth magnesium alloy prepared in this example has a tensile strength of 320MPa at room temperature, a yield strength of 215MPa, and an elongation of 7%; a tensile strength of 295MPa at 200°C, a yield strength of 205MPa, and an elongation of 15%; Under the condition of 80MPa, the creep deformation after 100 hours is 0.067%.

Example 5

This embodiment relates to a silicon-containing heat-resistant rare earth magnesium alloy, which contains the following components by weight percentage: 6%Gd, 6%Y, 0.3%Si and 0.8%Zr, and the rest is Mg and unavoidable impurities , wherein the content of impurity elements is: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca<0.01%.

This embodiment also relates to the preparation method of the aforementioned silicon-containing heat-resistant rare earth magnesium alloy. The method includes: the method includes: raw material preheating, smelting and subsequent heat treatment:

Step 1, raw material preheating: preheat raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy to 220°C;

Step 2, smelting: carried out under the protection of magnesium alloy flux containing MgCl ₂ , KCl, CaF ₂ , including the following steps:

(1) Magnesium addition: Add pure magnesium to the resistance crucible furnace for smelting; (2) Add Si: After magnesium is completely melted, add Mg-Si master alloy at 680°C and stir for 5 minutes; (3) Add Gd And Y: add Mg-Gd master alloy after heating up to 740°C, add Mg-Y master alloy when the temperature of magnesium liquid rises to 740°C; (4) Add Zr: raise the temperature of magnesium liquid to 790°C and add Mg-Zr intermediate Alloys; (5) Refining: After holding at 780°C for about 10 minutes, continue electric refining for 10 minutes, and the refining process needs to be fully stirred; (6) Casting: After refining, stand at 770°C for 25 minutes, and wait for the magnesium liquid to cool to 710°C Skim off the dross, cast with a metal mold, and preheat the steel mold for casting to 240°C, and then get a silicon-containing heat-resistant rare earth magnesium alloy;

Step 3, subsequent heat treatment: at a temperature of 520°C, perform solution treatment for 4 hours, and then at a temperature of 200°C, perform aging treatment for 48 hours.

Implementation effect: the silicon-containing heat-resistant rare earth magnesium alloy prepared in this example has a tensile strength of 310MPa at room temperature, a yield strength of 210MPa, and an elongation of 8%; a tensile strength of 290MPa at 200°C, a yield strength of 200MPa, and an elongation of 14%; Under the condition of 80MPa, the creep deformation after 100 hours is 0.07%.

In summary, the present invention achieves excellent room temperature and high temperature strength and plasticity under a reasonable total amount of rare earth elements, and improves the wear resistance of the alloy while maintaining the heat resistance of the alloy, and obtains an excellent comprehensive performance of the alloy. hot magnesium alloy.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications made to the above embodiments according to the technical essence of the present invention are not deviated from the content of the technical solution of the present invention. , equivalent changes and modifications all belong to the scope of the technical solution of the present invention.

Claims (10)

1. A silicon-containing heat-resistant rare earth magnesium alloy, characterized in that the alloy comprises the following components in weight percentage: Gd 5～10%, Y 2～8%, Si 0.3～2%, Zr 0.35～0.8%, Among them, the sum of the content of Gd and Y is 11-13%, Impurities are less than 0.02%, The balance is magnesium. 2. The silicon-containing heat-resistant rare earth magnesium alloy according to claim 1, characterized in that, the components of the impurities and their weight percentages are: Fe<0.005%, Cu<0.005%, Ni<0.002%, Ca< 0.01%. 3. A method for preparing a silicon-containing heat-resistant rare earth magnesium alloy as claimed in claim 1, wherein the method comprises: raw material preheating, smelting and subsequent heat treatment: Step 1, raw material preheating: preheating raw material magnesium ingot, Mg-Si, Mg-Gd, Mg-Y and Mg-Zr master alloy; Step 2, smelting: the smelting is carried out under the protection of flux or SF ₆ and CO ₂ mixed gas, including the following steps: Step 2.1, heating and melting the magnesium ingot; Step 2.2, after the magnesium ingot is completely melted, add Mg-Si master alloy and stir, then add Mg-Gd master alloy, Mg-Y master alloy, Mg-Zr master alloy in turn, keep warm, add refining agent to refine, let stand, Slag removal, ladle casting or low pressure casting to obtain silicon-containing heat-resistant rare earth magnesium alloy; Step 3, subsequent heat treatment: includes the following steps: The heat-resistant rare earth magnesium alloy containing silicon is subjected to solution treatment and aging treatment. 4. The method for preparing silicon-containing heat-resistant rare earth magnesium alloy according to claim 3, characterized in that, in step 1, the preheating temperature is 180-220°C. 5. The preparation method of silicon-containing heat-resistant rare earth magnesium alloy as claimed in claim 3, characterized in that, in step 2.2, when the temperature of the magnesium liquid is 660-680° C., the Mg-Si master alloy is added, and the stirring time is 3-680° C. 5 minutes; when the temperature of the magnesium liquid is 730-750°C, add the Mg-Gd master alloy; when the temperature of the magnesium liquid rises to 730-750°C and stabilize, add the Mg-Y alloy; when the temperature of the magnesium liquid is 780-790°C, add Mg - Zr master alloy, the holding temperature is 780° C., and the holding time is 5-15 minutes. 6. The method for preparing silicon-containing heat-resistant rare earth magnesium alloy according to claim 3, characterized in that, in step 2.2, the refining time is 5 to 15 minutes, and the resting temperature is 760 to 780°C. The standing time is 20-30 minutes, and the slag removal temperature is 700-720°C. 7. The method for preparing silicon-containing heat-resistant rare earth magnesium alloy according to claim 3, characterized in that, in the step 3, the temperature of the solution treatment is 480-520°C, and the time is 4-20h; The temperature of the aging treatment is 200-250° C., and the time is 8-50 hours. 8. The preparation method of silicon-containing heat-resistant rare earth magnesium alloy as claimed in claim 3, characterized in that, the mass fraction of magnesium in the magnesium ingot is >99.9%, and the flux and refining agent contain MgCl ₂ , KCl, CaF ₂ magnesium alloy flux. 9. the preparation method of silicon-containing heat-resistant rare earth magnesium alloy as claimed in claim 3 is characterized in that, described SF ₆ and CO ₂ The volume percentage of SF ₆ in the mixed gas is 0.2%. 10. The method for preparing the silicon-containing heat-resistant rare earth magnesium alloy according to claim 3, characterized in that stirring is accompanied during the refining process.