Method for improving mechanical property of Mg-Y-Zn alloy

Abstract

The invention discloses a method for improving the mechanical property of an Mg-Y-Zn alloy. The method comprises the following steps: (1) smelting a smelting raw material to obtain an alloy melt; (2) casting the alloy melt to obtain an as-cast alloy; (3) carrying out solution treatment on the as-cast alloy at 450-550 DEG C for 5-20 hours, and then carrying out water cooling to obtain an Mg-Y-Zn alloy; the Mg-Y-Zn alloy comprises the following components in percentage by weight: 5 to 13 percent of Y, 1.3 to 2.3 percent of Zn, 0.8 to 1.5 percent of Gd, 0.1 to 0.8 percent of Zr, 0.1 to 0.5 percent of Ca and 83 to 92 percent of Mg. By means of the method, the mechanical property of the Mg-Y-Zn alloy can be improved.

Description

Technical Field

[0001] The invention relates to a method for improving the mechanical properties of a Mg-Y-Zn alloy. Background Art

[0002] Magnesium alloys have the advantages of low density, high specific strength, and easy recycling, and have broad application prospects in the fields of mechanical equipment, automobiles, and aerospace. However, magnesium alloys have disadvantages such as low absolute strength and limited room temperature plasticity. Compared with other magnesium alloys, Mg-Zn-Y ternary alloy has relatively excellent mechanical properties, but its strength and plasticity still need to be further improved. Summary of the invention

[0003] The purpose of the present invention is to provide a method for improving the mechanical properties of Mg-Y-Zn alloys, which can effectively improve the mechanical properties of Mg-Y-Zn alloys. The present invention achieves the above technical purpose through the following technical solutions.

[0004] The present invention provides a method for improving the mechanical properties of Mg-Y-Zn alloy, comprising the following steps:

[0005] (1) smelting raw materials to obtain an alloy melt;

[0006] (2) casting the alloy melt to obtain a cast alloy;

[0007] (3) treating the as-cast alloy at 450-550° C. for 5-20 h, and then water cooling to obtain a Mg-Y-Zn alloy;

[0008] The Mg-Y-Zn alloy comprises 5-13wt% Y, 1.3-2.3wt% Zn, 0.8-1.5wt% Gd, 0.1-0.8wt% Zr, 0.1-0.5wt% Ca and 83-92wt% Mg.

[0009] The mechanical properties described in the present invention include tensile strength, yield strength and elongation.

[0010] According to the method of the present invention, preferably, the solution temperature is 460-500°C and the solution time is 6-10 hours. More preferably, the solution temperature is 480-490°C. More preferably, the solution time is 8-9 hours. Such solution conditions can form LPSO phase in the Mg-Y-Zn alloy of the present invention. The optimal solution conditions of the present invention can significantly increase the content of LPSO phase in the Mg-Y-Zn alloy, and improve the tensile strength, yield strength and elongation of the Mg-Y-Zn alloy.

[0011] According to the method of the present invention, preferably, the Mg-Y-Zn alloy comprises 7-11wt% Y, 1.5-2.1wt% Zn, 1-1.3wt% Gd, 0.2-0.6wt% Zr, 0.1-0.4wt% Ca and 85-90wt% Mg.

[0012] Preferably, in the Mg-Y-Zn alloy, the content of Y is 9-10wt%, the content of Zn is 1.8-2wt%, the content of Gd is 1.1-1.2wt%, the content of Zr is 0.3-0.4wt%, the content of Ca is 0.2-0.3wt%, and the content of Mg is 87.3-88wt%. Such an alloy composition can improve the tensile strength, yield strength and elongation of the alloy.

[0013] According to the method of the present invention, preferably, the Mg-Y-Zn alloy is composed of Y, Zn, Gd, Zr, Ca and Mg. Of course, the Mg-Y-Zn alloy may contain inevitable impurities. The content of impurities may be ≤0.2wt%.

[0014] According to the method of the present invention, preferably, step (1) comprises the following steps:

[0015] The smelting raw materials are smelted at 700-780°C in the presence of a protective gas consisting of SF6 and an inert gas.

[0016] According to the method of the present invention, preferably, step (1) comprises the following steps:

[0017] The raw materials are smelted at 700-730° C. in the presence of a protective gas consisting of SF6 and an inert gas until the raw materials are melted, and then smelted at 740-760° C. for 1-4 hours under stirring to obtain a smelting product; after the smelting product is allowed to stand, scum on the surface is skimmed off to obtain an alloy melt.

[0018] In certain embodiments, the smelting raw materials are smelted at 710-720° C. in the presence of a protective gas consisting of SF6 and an inert gas until the smelting raw materials are melted, and then smelted at 750-755° C. for 2-3 hours under stirring conditions to obtain a smelting product; after the smelting product is allowed to stand for 20-40 minutes, the slag on the surface is skimmed off to obtain an alloy melt.

[0019] The inert gas is selected from one or more of nitrogen, helium, neon and argon. Preferably, the inert gas is nitrogen. The volume ratio of SF6 to the inert gas can be 1:(20-90); preferably 1:(30-70); more preferably 1:(40-50). This can reduce the impurity content in the alloy melt and improve the mechanical properties of the alloy.

[0020] According to the method of the present invention, preferably, in step (2), the alloy melt at a temperature of 700-750° C. is cast to obtain a cast alloy. More preferably, the alloy melt at a temperature of 730-740° C. is cast to obtain a cast alloy. Gravity casting can be used.

[0021] The casting mold may be heated to 100-300°C before casting; preferably 150-250°C.

[0022] In step (3), the alloy after solid solution is cooled to room temperature by water cooling. The room temperature can be 20 to 38° C., preferably 25 to 30° C. This helps to form the LPSO phase in the alloy.

[0023] Solution treatment can be carried out in an aging furnace.

[0024] According to the method of the present invention, preferably, the following steps are also included: cutting and polishing the raw material to remove pollutants on the surface of the raw material to obtain treated raw material; forming the treated raw material into smelting raw material according to the composition of the Mg-Y-Zn alloy.

[0025] According to the method of the present invention, preferably, the raw materials include metal Mg, Mg-Gd master alloy, metal Zn, Mg-Ca master alloy, Mg-Zr master alloy and Mg-Y master alloy.

[0026] The content of Gd in the Mg-Gd master alloy may be 15-40 wt %; or 25-35 wt %.

[0027] The Ca content in the Mg-Ca master alloy may be 10 to 30 wt %; or 15 to 25 wt %.

[0028] The content of Zr in the Mg-Zr master alloy may be 10-35 wt %; or 20-30 wt %.

[0029] The content of Y in the Mg-Y master alloy may be 10 to 35 wt %; or 20 to 30 wt %.

[0030] The content of impurities in the Mg-Y-Zn alloy of the present invention is ≤0.5wt%; preferably, the content of impurities is ≤0.2wt%.

[0031] According to the method of the present invention, preferably, the Mg-Y-Zn alloy has a tensile strength of ≥220 MPa, a yield strength of ≥160 MPa, and an elongation of ≥3.5%.

[0032] The tensile strength of the Mg-Y-Zn alloy of the present invention is ≥220 MPa; preferably, the tensile strength is ≥300 MPa.

[0033] The yield strength of the Mg-Y-Zn alloy of the present invention is ≥160 MPa; preferably, the yield strength is ≥200 MPa.

[0034] The elongation of the Mg-Y-Zn alloy of the present invention is ≥3.5%; preferably, the elongation is ≥6%.

[0035] The invention adds Gd, Zr and Ca of specific composition to Mg, Y and Zn alloy of specific composition for modification, and combines with specific preparation process to improve the tensile strength, yield strength and elongation of Mg-Y-Zn alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the shape of the sample used to test the mechanical properties of the Mg-Y-Zn alloy in the present invention.

[0037] The reference numerals are as follows:

[0038] 1-rod; 2-head; 3-cone; 31-cambered surface. DETAILED DESCRIPTION

[0039] Here is the test method:

[0040] The tensile strength (UTS), yield strength (YS) and elongation (EL) are tested according to the method specified in "GB / T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method".

[0041] The samples used are as follows Figure 1 As shown. The specimen is in the shape of a dumbbell, which has a rod 1 and two heads 2 connected to both ends of the rod 1. The rod 1 is connected to the two heads 2 through a truncated cone 3 respectively. The upper bottom surface of the truncated cone 3 is connected to the rod 1 and has the same diameter as the rod 1. The lower bottom surface of the truncated cone 3 is connected to the head 2 and has the same diameter as the head 2. The side surface of the truncated cone 3 is a concave arc surface 31. The length of the rod 1 is 27.5 mm and the diameter is 5±0.05 mm. The total length of the rod 1 and the two truncated cones 3 is 34 mm. The diameter of the head 2 is 9 mm. The total length of the specimen (the sum of the lengths of the rod 1, the two truncated cones 3 and the two heads 2) is 64 mm. The original gauge length L0 is 25 mm.

[0042] The specific test steps are as follows: For each alloy, parallel specimens are selected at least at three different locations for tensile testing. Before the test, the specimens are ground in sequence using 800﹟, 1000﹟, and 2000﹟ sandpaper to ensure that the surface of the specimens is smooth and free of foreign matter. The specimens are subjected to tensile testing at room temperature using an Instron electronic universal material testing machine, and the tensile rate is set to 0.5mm / min.

[0043] The alloy components were analyzed by ICP (PerkinElmer, Plasma 400).

[0044] The Mg content is calculated by the following formula:

[0045] Mg content=100wt%-Y content-Zn content-Gd content-Zr content-Ca content.

[0046] Examples 1 to 2 and Comparative Example 1

[0047] Metal Mg (purity>99.9wt%), Mg-30Gd master alloy, metal Zn (purity>99.9wt%), Mg-20Ca master alloy, Mg-25Zr master alloy, and Mg-25Y master alloy are used as raw materials. An angle grinder is used to cut and polish the surface of the raw materials so that the surface of the raw materials has a metallic luster and is free of pollutants such as oxides and rust, thereby obtaining the treated raw materials.

[0048] Weigh the processed raw materials according to the composition of the alloy to form smelting raw materials. Place the smelting raw materials in a smelting furnace, introduce SF6 and N2 as protective gases in a volume ratio of 1:40 into the smelting furnace, and smelt at 720°C until the smelting raw materials are completely melted; then continue smelting at 750°C and under stirring for 2 hours to obtain a smelting product. After the smelting product is left to stand for 30 minutes, skim off the scum on the surface to obtain an alloy melt.

[0049] When the alloy melt is at 730°C, the alloy melt is cast by gravity casting to obtain a cast alloy. Before casting, the casting mold is heated to 200°C.

[0050] The cast alloy is placed in an aging furnace for solution treatment, and then water-cooled to 25° C. to obtain a Mg-Y-Zn alloy.

[0051] The Mg-Y-Zn alloy is composed of 9wt% Y, 1.8wt% Zn, 1.2wt% Gd, 0.4wt% Zr, 0.3wt% Ca and the balance Mg.

[0052] The solution temperature and solution time are shown in Table 1. The mechanical properties of the obtained Mg-Y-Zn alloy are shown in Table 1.

[0053] Table 1

[0054]

[0055] Comparative Examples 2 to 3

[0056] Except that the element composition of the Mg-Y-Zn alloy is shown in Table 2, the rest is the same as Example 1. The mechanical properties of the Mg-Y-Zn alloy are shown in Table 2.

[0057] Table 2

[0058]

[0059]

[0060] It can be seen from Examples 1-2 and Comparative Example 1 that the solution temperature and solution time have an important influence on the mechanical properties of the alloy. After the solution treatment, LPSO phase will precipitate at and within the grain boundaries, improving the mechanical properties of the alloy. If the temperature is too low, a good solution effect cannot be achieved, and the mechanical properties of the alloy are relatively low. If the temperature and time are increased, oversolution will occur, which will reduce the content of the LPSO phase and reduce the mechanical properties of the alloy.

[0061] It can be seen from Example 1 and Comparative Examples 2-3 that the composition of the alloy of the present invention has an important influence on the mechanical properties of the alloy, and an appropriate proportion of Gd, Zr and Ca can improve the mechanical properties of the alloy.

[0062] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be thought of by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for improving the mechanical properties of Mg-Y-Zn alloys, characterized in that: The steps include: (1) smelting raw materials to obtain an alloy melt; (2) casting the alloy melt to obtain a cast alloy; (3) treating the as-cast alloy at 450-550° C. for 5-20 h, and then water cooling to obtain a Mg-Y-Zn alloy; The Mg-Y-Zn alloy comprises 5-13wt% Y, 1.3-2.3wt% Zn, 0.8-1.5wt% Gd, 0.1-0.8wt% Zr, 0.1-0.5wt% Ca and 83-92wt% Mg.

2. The method according to claim 1, characterized in that: The solution temperature is 460-500°C, and the solution time is 6-10h.

3. The method according to claim 1, characterized in that: The Mg-Y-Zn alloy comprises 7-11 wt% Y, 1.5-2.1 wt% Zn, 1-1.3 wt% Gd, 0.2-0.6 wt% Zr, 0.1-0.4 wt% Ca and 85-90 wt% Mg.

4. The method according to claim 1, characterized in that The Mg-Y-Zn alloy consists of Y, Zn, Gd, Zr, Ca and Mg.

5. The method according to claim 1, characterized in that Step (1) comprises the following steps: The smelting raw materials are smelted at 700-780°C in the presence of a protective gas consisting of SF6 and an inert gas.

6. The method according to claim 1, characterized in that Step (1) comprises the following steps: The smelting raw material is smelted at 700-730° C. in the presence of a protective gas consisting of SF6 and an inert gas until the smelting raw material is melted, and then smelted at 740-760° C. for 1-4 hours under stirring conditions to obtain a smelting product; The smelted product is allowed to stand, and the scum on the surface is skimmed off to obtain an alloy melt.

7. The method according to claim 1, characterized in that In step (2), the alloy melt is cast at a temperature of 700-750° C. to obtain a cast alloy.

8. The method according to claim 1, characterized in that: The following steps are also included: The raw material is cut and polished to remove pollutants on the surface of the raw material to obtain a processed raw material; the processed raw material is formed into a smelting raw material according to the composition of the Mg-Y-Zn alloy.

9. The method according to claim 6, characterized in that The raw materials include metal Mg, Mg-Gd master alloy, metal Zn, Mg-Ca master alloy, Mg-Zr master alloy and Mg-Y master alloy.

10. The method according to any one of claims 1 to 9, characterized in that: The tensile strength of the Mg-Y-Zn alloy is ≥220MPa, the yield strength is ≥160MPa, and the elongation is ≥3.5%.

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