CN107245619B - A kind of strong high temperature resistant magnesium alloy of superelevation - Google Patents

Abstract

The invention relates to an ultrahigh-strength and high-temperature-resistant magnesium alloy. The mass percentage composition of the alloy is: Gd: 8.0‑9.6%, Y: 1.8‑3.2%, the ratio of Gd content to Y content: 3≤Gd/Y≤5, Zr: 0.3‑0.7%, Ag: 0.02‑0.5% , Er: 0.02‑0.3%, the ratio of Ag content to Er content is: 1≤Ag/Er≤3, of which Fe≤0.02%, Si≤0.02%, Cu≤0.005%, Ni≤0.003%, and the total impurity content is not More than 0.1%, the rest is Mg. By adding Ag and Er, large-scale ingots with a diameter of 300-630mm can be prepared, and components with an outer diameter of 1700mm can be prepared. The tensile strength of the alloy in the T6 state is ≥470MPa, and the yield strength is ≥400MPa; the tensile strength at 200°C is ≥350MPa, and the yield strength is ≥260MPa.

Description

An ultra-high-strength and high-temperature-resistant magnesium alloy

technical field

The invention relates to the field of magnesium alloys, in particular to a rare earth-containing ultrahigh-strength and high-temperature-resistant magnesium alloy.

Background technique

Magnesium alloy is currently the lightest metal structure material available, with high specific strength, high specific stiffness, and excellent damping performance, etc., and has broad application prospects in the fields of aviation, aerospace and automobile industries. However, the current application of magnesium alloys is far behind that of aluminum alloys. The reasons include: the high-strength and heat-resistant magnesium alloy billet with high rare earth content is prone to severe cracking during the semi-continuous casting process, and the surface is severely cold-shocked, resulting in the production of castings. The specifications of the ingot and the size of the final component are limited; the high-temperature strength is low, which makes it difficult to meet the high-temperature service requirements; the processing plasticity is poor, and the qualified rate of finished products is low. Mg-Gd-Y-Zr series alloys developed in recent years have higher room temperature and high temperature strength than Mg-Zn-Zr series and Mg-Al-Zn series, but their casting performance and plastic processing performance are poor, and it is difficult to meet the requirements of the aerospace industry. There is an urgent need for lightweight and high-strength materials in the preparation of large-scale components.

Contents of the invention

The purpose of the present invention is to provide an ultra-high strength and high temperature resistant magnesium alloy. The mass percentage composition of the alloy is: Gd: 8.0-9.6%, Y: 1.8-3.2%, the ratio of Gd content to Y content: 3≤Gd/Y≤5, Zr: 0.3-0.7%, Ag: 0.02-0.5% , Er: 0.02-0.3%, the ratio of Ag content to Er content is: 1≤Ag/Er≤3, impurities include Fe, Si, Cu, Ni and other inevitable impurity elements, of which Fe≤0.02%, Si≤0.02 %, Cu≤0.005%, Ni≤0.003%, the total impurity content does not exceed 0.1%, and the rest is Mg.

The mass percentage of the alloy component Gd is 8.5-9.6%.

The mass percentage of the alloy component Y is 2.0-3.0%.

The ratio of the alloy composition Gd to Y is: 3.5≤Gd/Y≤4.5.

The mass percentage of the alloy component Zr is 0.3-0.5%.

The mass percentage of the alloy component Ag is 0.02-0.4%.

The mass percentage of the alloy component Ag is 0.02-0.3%.

The mass percentage of the alloy component Er is 0.02-0.2%.

The ratio of the alloy composition Ag to Er is: 1.5≤Ag/Er≤2.5.

The total content of impurities is no more than 0.05%.

Adding rare earth elements such as Gd and Y to the magnesium alloy, after aging heat treatment, the alloy decomposes into the β' phase with high thermal stability, which can improve the high temperature strength of the alloy. However, when the content of rare earth elements is high, the casting performance of the alloy drops sharply, the large-size ingot cracks severely, and the processing plasticity decreases, resulting in an extremely low product qualification rate.

The present invention controls the ratio Gd/Y of the Gd content to the Y content in the alloy between 3-5, and its effect is that: Y can improve the high-temperature strength of the magnesium alloy, and if the Y content is too low, the high-temperature strength of the alloy will decrease; If the Y content is too high, the number and size of the Mg ₂₄ Y ₅ phase formed in the alloy will increase, and the bonding force between this phase and the matrix will be weak, resulting in the reduction of thermoplasticity and cracking of the alloy during hot working. Controlling Gd/Y between 3-5 can ensure that the alloy has both high temperature strength and good hot-working plasticity.

The present invention adds Ag in Mg-Gd-Y-Zr alloy, and its effect comprises the following points:

1. Adding 0.02-0.5% Ag can significantly reduce the melting point of Mg-Gd-Y-Zr alloy and improve the fluidity of alloy melt during casting. On the one hand, the increase in melt fluidity reduces the inhomogeneity of the melt temperature field in the mold, reduces the residual stress formed in the semi-continuous casting process of the large ingot, and effectively prevents the cracking of the ingot; on the other hand, the melt Increased fluidity reduces the number and depth of cold stops on the surface of the ingot, improves the surface quality of the ingot, and increases the pass rate of the ingot.

2. Adding 0.02-0.5% Ag can significantly refine the β' phase in the Mg-Gd-Y-Zr alloy, make its distribution more dispersed and uniform, and improve the aging strengthening effect of the alloy.

The present invention adds Er to Mg-Gd-Y-Zr alloy, and its effect is: the thermoplastic deformation of Mg-Gd-Y-Zr alloy is mostly carried out under the high temperature of 400-530 ℃, and the addition of Ag strengthens the dynamic decomposition of alloy, reduces The content of rare earth elements in the alloy solid solution, adding 0.02-0.3% Er to the alloy can offset the promotion effect of Ag on dynamic decomposition, ensure a high content of rare earth elements in the alloy solid solution after deformation, and obtain strong aging strengthening in the subsequent aging process Effect.

The addition of Ag and Er is critical to the properties of Mg-Gd-Y-Zr alloys. Excessively high Ag content will reduce the solubility of Gd and Y in magnesium alloys, resulting in a large amount of eutectic structure remaining after alloy homogenization treatment, and poor processing and plastic deformation; when Er content is >0.3%, the β′ strengthening phase formed by aging will be coarse To reduce the age strengthening effect of the alloy; the ratio of Ag content to Er content is controlled between 1-3, and the alloy has good processing plasticity and age strengthening effect at the same time.

By adding a small amount of Ag and Er, the casting performance, processing performance and aging strengthening effect of the alloy are greatly improved, large-scale components can be prepared, the pass rate and the room temperature and high temperature mechanical properties of the alloy can be improved. Large-scale high-quality ingots with a diameter of 300-630mm and a length ≥ 2000mm can be produced, and large-sized shell components with an outer diameter of 1700mm and small anisotropy can be prepared through integrated plastic deformation technology. Tensile strength ≥ 470MPa, yield strength ≥ 400MPa, elongation after fracture ≥ 5%; tensile strength at 200°C ≥ 350MPa, yield strength ≥ 260MPa, elongation after fracture ≥ 7%.

Using the same preparation method, adding Ag and Er in an appropriate amount, and ensuring that the Mg-Gd-Y-Zr-Ag-Er alloy with 1≤Ag/Er≤3, 3≤Gd/Y≤5 is more qualified than the alloy without Ag and Er The yield is increased from no more than 50% to more than 70%; the diameter of the largest ingot prepared is increased from 400mm to 630mm, and the diameter of the largest ring member prepared is increased from 700mm to 1700mm; the yield strength of the alloy at room temperature is increased by 10-15%, and it yields at 200°C Strength increased by 30-40%.

Using the same preparation method, the ratio of Gd content to Y content satisfies 3≤Gd/Y≤5 Mg-Gd-Y-Zr-Ag-Er alloy ratio Gd/Y<3 alloy product pass rate, room temperature strength and high temperature Strength is significantly improved.

Using the same preparation method, the room temperature strength and high temperature strength of the Mg-Gd-Y-Zr-Ag-Er alloy whose ratio of Gd content to Y content satisfies 3≤Gd/Y≤5 is significantly higher than that of the alloy with Gd/Y>5.

Using the same preparation method, add Ag and Er in an appropriate amount, and ensure that the Mg-Gd-Y-Zr-Ag-Er alloy ratio of 1≤Ag/Er≤3 has a ratio of Ag/Er>3 of the alloy product qualification rate, room temperature strength and high temperature Strength is significantly improved.

Using the same preparation method, adding Ag and Er in appropriate amounts, and ensuring that the Mg-Gd-Y-Zr-Ag-Er alloy with 1≤Ag/Er≤3 is significantly higher than the room temperature strength and high temperature strength of the alloy with Ag/Er<1.

Description of drawings

Fig. 1 is the transmission electron microstructure appearance of the alloy of Example 4 in the present invention.

Fig. 2 is the transmission electron microstructure appearance of the comparative example 1 alloy in the present invention.

Detailed ways

Example 1:

The chemical composition of magnesium alloy is: Gd: 9.0%, Y: 2.5%, Zr: 0.4%, Ag: 0.07%, Er: 0.04%, impurities include Fe, Si, Cu, Ni, Fe: 0.0015%, Si: 0.0025 %, Cu: 0.0006%, Ni: 0.002%, the total impurity content is 0.03%, and the rest is Mg. The magnesium alloy ingot was prepared by semi-continuous casting method. The ingot size was 450mm in diameter and 2700mm in length. The finished product was made after homogenization annealing and plastic deformation. The final pass rate of the shell product was 81%, and the finished product diameter was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 2

The chemical composition of magnesium alloy is: Gd: 9.5%, Y: 2.2%, Zr: 0.5%, Ag: 0.1%, Er: 0.05%, impurities include Fe, Si, Cu, Ni, Fe: 0.0026%, Si: 0.0022 %, Cu: 0.002%, Ni: 0.001%, the total impurity content is 0.014%, and the rest is Mg. The magnesium alloy ingot was prepared by semi-continuous casting method. The ingot size was 450mm in diameter and 1650mm in length. The finished product was made after homogenization annealing and plastic deformation. The final pass rate of the shell product was 71%, and the finished product diameter was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 3

The chemical composition of magnesium alloy is: Gd: 8.5%, Y: 2.3%, Zr: 0.4%, Ag: 0.5%, Er: 0.2%, impurities include Fe, Si, Cu, Ni, Fe: 0.0018%, Si: 0.002 %, Cu: 0.001%, Ni: 0.002%, the total impurity content is 0.025%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 450mm in diameter and 1700mm in length. After uniform annealing and plastic deformation, the finished product was produced. The final pass rate of the shell product was 70%, and the finished product diameter was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 4

The chemical composition of magnesium alloy is: Gd: 8.8%, Y: 2.2%, Zr: 0.3%, Ag: 0.3%, Er: 0.2%, impurities include Fe, Si, Cu, Ni, Fe: 0.0016%, Si: 0.003 %, Cu: 0.002%, Ni: 0.001%, the total impurity content is 0.03%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 630mm in diameter and 1700mm in length. The finished product was made after homogenization annealing and plastic deformation. The final pass rate of the shell product was 75%, and the finished product diameter was 1700mm. After treatment, its transmission electron microstructure is shown in Figure 1. It can be seen that its internal strengthening phase is finely dispersed. Tensile tests at room temperature and 200 °C were performed to obtain tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 5

The chemical composition of magnesium alloy is: Gd: 9%, Y: 2%, Zr: 0.5%, Ag: 0.2%, Er: 0.1%, impurities include Fe, Si, Cu, Ni, Fe: 0.003%, Si: 0.001 %, Cu: 0.003%, Ni: 0.002%, the total impurity content is 0.04%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 630mm in diameter and 1700mm in length. The finished product was made after homogenization annealing and plastic deformation. The final pass rate of the shell product was 82%, and the diameter of the finished product was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 6

The chemical composition of magnesium alloy is: Gd: 8.9%, Y: 2.5%, Zr: 0.4%, Ag: 0.15%, Er: 0.07%, impurities include Fe, Si, Cu, Ni, Fe: 0.001%, Si: 0.002 %, Cu: 0.004%, Ni: 0.001%, the total impurity content is 0.025%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 630mm in diameter and 1700mm in length. After uniform annealing and plastic deformation, the finished product was produced. The final pass rate of the shell product was 78%, and the finished product diameter was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Example 7

The chemical composition of magnesium alloy is: Gd: 8.9%, Y: 2.5%, Zr: 0.5%, Ag: 0.05%, Er: 0.03%, impurities include Fe, Si, Cu, Ni, Fe: 0.002%, Si: 0.004 %, Cu: 0.001%, Ni: 0.003%, the total impurity content is 0.03%, and the rest is Mg. The magnesium alloy ingot was prepared by semi-continuous casting method. The ingot size was 630mm in diameter and 1700mm in length. The finished product was made after homogenization annealing and plastic deformation. The final pass rate of the shell product was 70%, and the finished product diameter was 1700mm. After treatment, tensile tests at room temperature and 200°C were carried out to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 1.

Comparative example 1:

The chemical composition of magnesium alloy is: Gd: 8.5%, Y: 2.7%, Zr: 0.4%, impurities include Fe, Si, Cu, Ni, impurities include Fe, Si, Cu, Ni, Fe: 0.001%, Si: 0.002 %, Cu: 0.003%, Ni: 0.001%, the total impurity content is 0.04%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The size of the ingots was 400mm in diameter and 2000mm in length. After uniform annealing and plastic deformation, the finished product was produced. The qualified rate of the product was 40%. The diameter of the finished shell was 1200mm. Finally, its transmission electron microstructure is shown in Figure 2. It can be seen that its β' is thicker than that in Example 4. Do tensile tests at room temperature and 200°C to obtain tensile strength, yield strength and elongation after fracture. The specific data See Table 2. It can be seen that no Ag and Er elements are added to the magnesium alloy of Comparative Example 1, and its maximum ingot size, maximum product size, product qualification rate, room temperature strength, and high temperature strength are all significantly lower than those of Examples 1-7.

Comparative example 2:

The chemical composition of magnesium alloy is: Gd: 8.5%, Y: 3.2%, Zr: 0.4%, Ag: 0.5%, Er: 0.18%, impurities include Fe, Si, Cu, Ni, Fe: 0.003%, Si: 0.002 %, Cu: 0.004%, Ni: 0.002%, the total impurity content is 0.02%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The size of the ingots was 400mm in diameter and 2000mm long. The finished product was made after homogenization annealing and plastic deformation. The qualified rate of the product was 35%. The diameter of the finished shell was 1200mm. Finally, do tensile tests at room temperature and 200°C to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 2. It can be seen that the pass rate, room temperature strength, and high temperature strength of the magnesium alloy product of Comparative Example 2 are significantly lower than those of Examples 1-7.

Comparative example 3:

The chemical composition of magnesium alloy is: Gd: 9.5%, Y: 1.8%, Zr: 0.4%, Ag: 0.5%, Er: 0.18%, impurities include Fe, Si, Cu, Ni, Fe: 0.003%, Si: 0.004 %, Cu: 0.001%, Ni: 0.002%, the total impurity content is 0.02%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The size of the ingots was 600mm in diameter and 2000mm in length. After uniform annealing and plastic deformation, the finished product was produced. The qualified rate of the product was 75%. The diameter of the finished shell was 1200mm. Finally, do tensile tests at room temperature and 200°C to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 2. It can be seen that the room temperature strength and high temperature strength of the magnesium alloy of Comparative Example 3 are significantly lower than those of Examples 1-7.

Comparative example 4:

The chemical composition of magnesium alloy is: Gd: 9.5%, Y: 1.8%, Zr: 0.4%, Ag: 0.5%, Er: 0.1%, impurities include Fe, Si, Cu, Ni, Fe: 0.003%, Si: 0.002 %, Cu: 0.004%, Ni: 0.002%, the total impurity content is 0.02%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 600mm in diameter and 2000mm in length. The finished product was made after homogenization annealing and plastic deformation. The qualified rate of the product was 40%. The diameter of the finished shell was 1200mm. Finally, do tensile tests at room temperature and 200°C to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 2. It can be seen that the qualification rate, room temperature strength, and high temperature strength of the magnesium alloy product of Comparative Example 4 are significantly lower than those of Examples 1-7.

Comparative example 5:

The chemical composition of magnesium alloy is: Gd: 9.5%, Y: 1.8%, Zr: 0.4%, Ag: 0.15%, Er: 0.3%, impurities include Fe, Si, Cu, Ni, Fe: 0.004%, Si: 0.001 %, Cu: 0.003%, Ni: 0.002%, the total impurity content is 0.02%, and the rest is Mg. Magnesium alloy ingots were prepared by semi-continuous casting. The ingot size was 400mm in diameter and 2000mm in length. The finished product was made after homogenization annealing and plastic deformation. The qualified rate of the product was 73%. The diameter of the finished shell was 1200mm. Finally, do tensile tests at room temperature and 200°C to obtain the tensile strength, yield strength and elongation after fracture. The specific data are shown in Table 2. It can be seen that the room temperature strength and high temperature strength of the magnesium alloy of Comparative Example 5 are significantly lower than those of Examples 1-7.

Table 1 Example alloy mechanical properties

Table 2 Mechanical properties of comparative alloys

Claims (10)

1. a kind of strong high temperature resistant magnesium alloy of superelevation, it is characterised in that alloy mass percent composition is：Gd：8.0-9.6%, Y： 1.8-3.2%, Gd content and the ratio of Y contents are：3≤Gd/Y≤5, Zr：0.3-0.7%, Ag：0.02-0.5%, Er：0.02- 0.3%, Ag content and the ratio of Er contents are：1≤Ag/Er≤2.5, impurity includes Fe, Si, Cu, Ni and other are inevitable Impurity element, wherein Fe≤0.02%, Si≤0.02%, Cu≤0.005%, Ni≤0.003%, content of impurities are no more than 0.1%, Surplus is Mg.

2. the strong high temperature resistant magnesium alloy of superelevation according to claim 1, it is characterised in that：The quality percentage of the alloying component Gd Than for 8.5-9.6%.

3. the strong high temperature resistant magnesium alloy of superelevation according to claim 2, it is characterised in that：The quality percentage of the alloying component Y Than for 2.0-3.0%.

4. the strong high temperature resistant magnesium alloy of superelevation according to claim 1, it is characterised in that：The ratio of the alloying component Gd and Y For：3.5≤Gd/Y≤4.5.

5. the strong high temperature resistant magnesium alloy of superelevation according to claim 4, it is characterised in that：The quality percentage of the alloying component Zr Than for 0.3-0.5%.

6. the strong high temperature resistant magnesium alloy of superelevation according to claim 5, it is characterised in that：The quality percentage of the alloying component Ag Than for 0.02-0.4%.

7. the strong high temperature resistant magnesium alloy of superelevation according to claim 6, it is characterised in that：The quality 100 of the alloying component Ag Divide than being 0.02-0.3%.

8. the strong high temperature resistant magnesium alloy of superelevation according to claim 7, it is characterised in that：The quality percentage of the alloying component Er Than for 0.02-0.2%.

9. the strong high temperature resistant magnesium alloy of superelevation according to claim 1, it is characterised in that：The ratio of the alloying component Ag and Er For：1.5≤Ag/Er≤2.5.

10. the strong high temperature resistant magnesium alloy of superelevation according to claim 8, it is characterised in that：Content of impurities is no more than 0.05%.