CN1938441A - High-strength-toughness magnesium alloy and its preparing method - Google Patents

Abstract

The invention relates to a high-strength and high-toughness casting magnesium alloy and a preparation method thereof. In terms of weight percentage, the aluminum content in the alloy of the present invention is 3-9wt%, the zinc content is 3.5-9wt%, the manganese content is 0.15-1.0wt%, the antimony content is 0.01-2wt%, and the magnesium content is the balance balance; The alloy may further contain 0-2wt% of a certain element of one of cerium-rich mixed rare earth, calcium and silicon. After T6 (solution + aging) heat treatment of the typical alloy of the present invention, its mechanical properties at room temperature can reach: tensile strength σ _b ≥ 270MPa, yield strength σ _0.2 ≥ 140MPa, elongation δ ₅ ≥ 6%, Brinell hardness ≥ 70, impact energy α _k ≥ 12J. Certain alloys of the present invention can not only have excellent room temperature mechanical properties, but also have excellent high temperature mechanical properties at the same time. The alloy of the invention has low preparation cost and is suitable for large-scale production. The alloy of the invention is suitable for casting processes such as metal mold casting, sand casting, pressure casting, squeeze casting and the like.

Description

A kind of high-strength high-toughness magnesium alloy and preparation method thereof Technical field

The invention relates to a cast gold and its preparation technology. The purpose of the invention is to prepare a low-cost, high-strength and high-toughness casting magnesium alloy by means of alloying and heat treatment. The present invention is not only suitable for metal permanent mold casting, but also suitable for sand casting, pressure casting, squeeze casting and other processes. Background technique

As a light metal material, magnesium alloy has many advantages, such as high specific strength, excellent machining and casting properties, good damping characteristics, dimensional stability, and electromagnetic shielding ability. Due to the above characteristics, magnesium alloy parts have been widely used in many industrial sectors, including automobile manufacturing, 3C product (computer, communication, consumer electronics) manufacturing, military industry, etc. In recent years, due to the increasingly urgent demand for weight reduction of automobiles, the low density of magnesium alloys has made it extremely attractive again in the field of transportation. The demand for mirror alloys has experienced a period of rapid growth.

However, relative to aluminum alloys, weaker strength and/or plasticity severely limit the application of magnesium alloys (for example, applications such as light-duty automobile hubs, etc., require high strength and high toughness at the same time). Table 1 shows the tensile mechanical properties of some typical commercial cast magnesium alloys. Tensile mechanical properties of typical cast magnesium alloys Composition (weight percent)

^ Tensile properties

δ ₅(%)A1 Zn Mn Zr Other σ _b (MPa)

δ ₅ (%)

C die casting)

AM60 6.0 - 0.3 - - 220 115 8

AZ91 9.0 0.7 0.3 - - 230 150 3

(casting:)

ZE63 - 5.8 - 0.7 2.6RE 300 190 10 It can be seen from Table 1 that the most widely used die casting ^ AZ91 alloy has high strength, but its low plasticity limits its application. In addition, although AM60 alloys have high plasticity, their low strength also limits their mass application. Although there are a small amount of magnesium-rare earth alloys with high strength and high toughness at the same time, such as ZE63, the high cost and complicated heat treatment process make it difficult for these alloys to be applied in large areas. Due to increased slow The strength and plasticity of alloys are the key to further expand the application range of magnesium alloys. Therefore, it is a very urgent task to develop a low-cost, high-strength and high-toughness magnesium alloy.

Although there have been many attempts to improve the tensile mechanical properties of magnesium alloys, most of them have focused on improving the high temperature tensile mechanical properties of magnesium alloys, and the improvement of the normal temperature mechanical properties of these alloys is limited. For example, European patent 0879898A1 discloses a magnesium alloy with excellent high temperature performance and pressure casting performance, but the alloy disclosed in this invention has low room temperature strength (tensile strength<230 MPa) and plasticity (elongation<230 MPa) 5%). US Patent 20030084968A1 discloses a high-strength creep-resistant magnesium alloy, but the alloy disclosed in this invention also has low room temperature plasticity (elongation < 5%). US Patent 6139651 discloses a continuous alloy for high temperature applications, but the room temperature strength and plasticity of the alloy disclosed in this invention are not ideal. Although a few patents have obtained some promising high-strength and high-toughness magnesium alloys, such as US patent 20010055539A1, the development of more ideal room-temperature high-strength and high-toughness magnesium alloys still needs to be further developed.

In recent years, although the role of trace elements (rare earth elements, beryllium, bismuth, strontium, antimony, etc.) on the creep resistance performance. For example, Chinese patent CN1401804 discloses a heat-resistant magnesium alloy, which contains 2-10 wt% (weight percentage, the same below) of aluminum, 0.2-2 wt% of zinc, 0.1-0.6 wt% of manganese, 0.1-2 wt% bismuth, 0.1-1.5 wt% antimony, others magnesium. European Patent No. 1241276 discloses a creep resistant alloy containing 1.5-4.0 wt% aluminum, 0.5-1.8 wt% silicon, 0.05-0.6 wt% rare earth, 0.005-1.5 wtty. Strontium or antimony, magnesium is the balance balance. Chinese patent CN1341767 discloses a multi-component automotive heat-resistant magnesium alloy and its casting process. The alloy contains 5-7 wt% aluminum, 0.5-1.0 wt% zinc, 0.6-1.5 wt% silicon, 0.4- 0.7 wt% antimony, 0.1-0.3 wt% rare earth, 0.002 wt% beryllium, magnesium is the balance balance.

Based on the analysis of a large number of literatures, we noticed that in the magnesium-aluminum-zinc ternary die-casting area with medium aluminum content and medium zinc content, if appropriate trace elements are used and appropriate heat treatment is used, there may be development The potential of developing low-cost, high-strength and high-toughness magnesium alloys. As a result, we found some magnesium alloys with these properties, which are discussed in detail below. Contents of the invention

The main purpose of the present invention is to provide a cast magnesium alloy with both high strength and high toughness by rationally selecting alloying elements and adopting appropriate heat treatment means.

The second purpose of the present invention is that the gold alloy prepared by this method is not only suitable for permanent mold casting, but also suitable for sand casting, pressure casting, squeeze casting and other processes. The third purpose of the present invention is that the magnesium alloy prepared by this method not only has excellent room temperature mechanical properties, but some alloys also have excellent high temperature mechanical properties.

The fourth object of the present invention is that the magnesium alloy prepared by this method has the above-mentioned characteristics, and the production cost of the alloy is relatively low.

The most important discovery of the present invention is that: medium aluminum content and medium zinc content constitute the basic system of high-strength and high-toughness magnesium alloy; the addition of trace elements and appropriate heat treatment process further make the alloy achieve the best mechanical properties.

In terms of weight percentage, the aluminum content in the alloy of the present invention is 3-9 wt%; the zinc content is 3.5-9 wt%; the manganese content is 0.15-1.0 wt% _; the antimony content is 0.01-2 wt% _; The balance; the alloy may further contain 0 to 2 wt% of a certain element of one of cerium-rich mixed rare earths, calcium and silicon.

The strengthening and toughening mechanism of the present invention is as follows: 1) The solid solution strengthening mechanism of elements. 2), Secondary extruded phase strengthening mechanism: With the increase of zinc content, the Mg ₁₇ Al ₁₂ phase gradually decreases, while the Mg-Al-Ζη ternary phase and the magnesium-zinc binary phase gradually increase; in addition, adding Mn, Sb, etc. After adding trace elements, new particle reinforcement phases or particles such as Al-Mn, M^Sba, etc. will be produced. 3), the addition of certain elements (such as antimony) will also refine the grains and the continuous brittle secondary precipitates distributed on the grain boundaries, thereby improving the strength, plasticity and casting performance of the alloy. 4), the advanced heat treatment process will further improve the mechanical properties of the alloy by adjusting the number and shape of the secondary precipitates.

Aluminum (A1): 3~9 wt%

Aluminum element is not only very effective for increasing the room temperature strength and hardness of gold, but also makes ^^ gold easier to cast by widening the solidification range of the alloy. In order to obtain a significant strengthening effect, the aluminum content in the alloy should be at least 3wt% _; however, too high aluminum content will adversely affect the plasticity of the alloy. Therefore, the upper limit of the aluminum content of the alloy in the present invention is 9 t%.

Zinc (Zn): 3.5~9 wt%

In magnesium alloys, zinc is another important alloying element besides aluminum. Zinc and aluminum are used together in the present invention to enhance the room temperature strength and castability of the alloy. However, it is well known that in the magnesium-aluminum-zinc alloy system, if the matching of zinc and aluminum is not suitable, the hot cracking tendency of the alloy will be increased and the casting performance will be deteriorated. The present invention is based on the relationship between the die-casting performance of the magnesium-aluminum-zinc ternary alloy system and the content of aluminum and zinc (see accompanying drawing 1), by selecting the appropriate content of aluminum and zinc, and under the action of certain trace elements (such as antimony) , so as to obtain a magnesium alloy with a lower hot cracking tendency on the basis of ensuring the die-casting performance of the alloy. Therefore, the zinc content in the alloy of the present invention should be a minimum of 3.5 wt%. In addition, the highest zinc content should not exceed 9 wt%, since excessive zinc content will reduce the plasticity of the alloy.

Manganese (Mn): 0.15-1 wt% The manganese element in the alloy of the present invention is added in the form of an aluminum-manganese master alloy. Although the effect of Mn on improving the tensile strength of the alloy is not obvious, it can play some role in increasing the yield strength through the Al-Mn particle phase present in the primary grains. The main function of manganese in the present invention is to improve the corrosion resistance of the alloy. During the alloy smelting process, manganese can form compounds with impurity elements in the alloy (such as iron, nickel, etc.), precipitate to the bottom of the crucible, remove impurities, and eliminate the harmful effects of these elements on the corrosion resistance of the alloy. The addition of manganese is limited by its low solid solubility, and the addition of manganese in the present invention is 0.15-1 wt%.

Antimony (Sb); 0.01-2 wt%

The antimony element in the present invention is either added in the form of powder wrapped in aluminum foil, or added in the form of block. A small amount of antimony will refine the primary crystal grains and secondary precipitates, thereby improving the mechanical properties of the alloy and reducing the tendency of hot cracking. However, when the antimony content exceeds ¾2 wt%, the coarsened _Mg3Sb2 particles will reduce the mechanical properties instead. Therefore, the antimony content in the present invention should be controlled at 0.01%~2wt%.

Other elements: 0-2 wt%

The alloy in the present invention may further contain 0-2 wt% of a certain element of one of cerium-rich misch, calcium and silicon.

The cerium-rich mixed rare earth in the present invention is a commercially available product, and its manufacturer is Baotou Huamei Rare Earth Hi-Tech Co., Ltd. About 50% of the cerium-rich mixed rare earth is cerium, and the other main components are lanthanum and neodymium. The addition of a small amount of rare earth can improve the hardness and high-temperature mechanical properties of magnesium alloys, but excessive rare earth will increase the cost on the one hand, and on the other hand will produce coarse grain precipitates and lead to the decline of mechanical properties and casting properties. Rare earth content should be controlled at 0-2 wt%, more ideally limited at 0-1 wt%.

The addition of calcium element will not only play the role of flame retardancy, but also improve the high temperature mechanical properties and creep resistance of the alloy. However, the addition of calcium reduces the castability and aggravates the hot cracking tendency of the alloy.

The addition of silicon will also improve the high-temperature mechanical properties and creep resistance of the alloy, but too much silicon will produce coarse MS grains and lead to a decrease in mechanical properties.

The smelting and casting process of alloy among the present invention can be divided into following several steps:

1) First set the target temperature of the crucible to 700~75 (TC, start heating; then put the various ingredients in the oven to preheat to

140 ~ 200 ° C, and at the same time, put a covering agent (commonly used covering agent for magnesium alloys) that accounts for 0.6% of the total weight of the alloy into the oven for baking; Preheat to 20040 (TC in the box-type furnace.

2) When the temperature of the crucible rises to 280~320°C, inject _CO2 gas into the crucible for gas replacement, then add Λ30%~50% of the baked covering agent to the bottom of the crucible, and then put the preheated The pure magnesium ingredients are put into the crucible. 3) After the pure magnesium ingredients are melted and the temperature of the crucible is stabilized at 700-750° C., various preheated ingredients are added sequentially according to the melting point from high to low, and then the melt is stirred for about 8-10 minutes; during this process, as appropriate, Add the remaining baked-on covering, whichever is non-combustible.

4) After the temperature of the crucible is stabilized at 700~750°C, the melt is left to stand for 4~6 minutes, and the melt is taken out under the protection of 99~99.5% air (or C0 ₂ ) + 0.5~1% SF ₆ mixed gas according to volume percentage surface scum;

5) After slag removal, keep the crucible temperature at 700~750. C, by volume percentage, cast under the protection of 99~99.5% air (or C0 ₂ ) + 0.5-1% SF ₆ mixed gas.

The heat treatment of the present invention affects the mechanical properties of the alloy to a great extent. The alloy heat treatment methods of the present invention can be divided into three types: T4 (solution treatment), T5 (aging treatment), and T6 (aging treatment after solution treatment), which will be introduced respectively below. , .

T4 solid solution treatment is best carried out in a protective atmosphere (such as argon, 99~99.5% air (or C0 ₂ ) + 0.5-1% SF ₆ mixed gas, etc.), the temperature range is 340 0 (TC and the zinc content Closely related. Generally speaking, the solid solution temperature of magnesium alloy should be 10~20°C lower than the solidus temperature of the alloy. The solidus temperature of the magnesium-aluminum-zinc ternary alloy system can refer to Figure 2. In addition, The addition of some elements (such as antimony) will have a slight effect on the solidus temperature, therefore, a more accurate solidus temperature can be determined by the differential thermal analysis data of the alloy. As for the time of T4 solid solution treatment, it can be taken as 8~24 Hour.

The temperature of T5 aging treatment is taken as 70-200°C, and the time of aging treatment is taken as 8-24 hours. As for T6 heat treatment, it can be understood as a combination of T4 and T5 heat treatment. Specifically, T4 heat treatment is carried out first, and then T5 heat treatment is carried out.

Since the heat treatment changes the distribution and quantity of the particle-reinforced phase, it significantly affects the mechanical properties. Generally speaking, the plasticity and impact resistance of T4 solid solution treated samples will be improved due to the re-dissolution of the mesophase into the matrix, but the yield strength will be reduced. T5 aging treatment can eliminate residual stress and improve mechanical properties to a certain extent. Because T6 treatment can redistribute the quantity and shape of secondary precipitates, it can significantly improve the strength and hardness of the alloy, but the plasticity of the alloy will decrease.

After T6 (solid solution + aging) heat treatment of the typical alloy of the present invention, its mechanical properties at room temperature can reach: tensile strength cj _b 270MPa, yield strength. ^ ^. ^^, extension ₅ 6%, Brinell hardness 70, impact energy ot _k 12J.

The present invention has the following advantages:

1) The magnesium alloy prepared by the present invention has the characteristics of high strength and high toughness, and is especially suitable for the material requirements of light weight, high strength and high toughness, such as automobile hubs and the like.

2) The magnesium alloys prepared by the present invention not only have excellent room temperature mechanical properties, but some alloys also have better high temperature mechanical properties. 3) The present invention has high cost performance. The raw materials used are easy to obtain, low in cost, and suitable for large-scale production.

4) The smelting and casting process of the present invention is simple and stable. The alloying elements used in the present invention do not have obvious side reactions with the iron crucible wall or covering agent, and the process is stable.

5) The present invention has a wide range of applicable processes. The present invention is not only suitable for metal mold casting, but also suitable for sand casting, pressure casting, squeeze casting and other processes. Description of drawings

Fig. 1 ¾ Vlg-Al-Zn ≡ elemental alloy die-casting performance and embodiment alloy location schematic diagram.

Figure 2 is a schematic diagram of the phase diagram (solid phase surface) of the Mg-Al-ZnH elemental alloy and the location of the alloy of the embodiment.

Fig. 3 is the DTA curve of the alloy of Example 1 of the present invention. , Figure 4 is the as-cast structure of the alloy of Example 1 of the present invention.

5 is a schematic diagram of the distribution of Mg3Sb ₂ in the alloy of Example 1 after T4 heat treatment, and the arrow marks in the figure indicate the distribution of Mg3Sb ₂ particles in the alloy of Example 1.

Fig. 6 is the structure of the alloy of Example 1 after T4 heat treatment.

Fig. 7 is the structure of the alloy of Example 1 after T6 heat treatment.

Figure 8 is a comparison of the mechanical properties at room temperature of three alloys (AM60, AZ9 Example 1) as cast.

Fig. 9 is a comparison of the mechanical properties at room temperature of the T6 heat treatment state of three alloys (AM60, AZ91, Example 1). Figure 10 is a comparison of the mechanical properties at room temperature of the T6 heat-treated state of four alloys (Example 1, Example 2, Example 3, and AZ91).

Figure 11 is a comparison of the 150 high temperature mechanical properties of the four alloys (Example 1, Example 2, Example 3, AZ91) in the T6 heat treatment state.

Figure 12 is a comparison of the mechanical properties at 150°C in the T6 heat treatment state of three alloys (Example 4, Example 5, AZ91). Detailed ways

Describe the high-strength and high-toughness magnesium alloy of the present invention in detail below in conjunction with embodiment:

Example 1

I ), alloy composition Three magnesium alloys were prepared in mild steel crucibles from commercially available high-purity raw materials. Among the three alloys, the commercial grade

AZ91 and test alloy ^ AM60 are comparative example alloys. The chemical composition of the three magnesium alloys was analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). See ¾2 for the chemical composition of three types of gold.

¾ 2. The chemical compositions of the three alloys ^ ¾ (weight percent wt %) ^ aluminum zinc manganese w magnesium

AZ91 9.00 1.03 0.29 - balance margin

AM60 5.92 - 0.28 - balanced

Example 1 5.88 3.89 0.30 0.51 Balance margin

II ), alloy smelting and casting

Alloy smelting was carried out in a 15 kg capacity crucible and resistance furnace. Crucibles and casting molds are made of mild steel. Taking Example 1 as an example, the smelting and casting process of the alloy will be described in detail below.

1) Set the target temperature of the crucible to 720°C, and start heating; then preheat various ingredients such as pure magnesium, pure aluminum, aluminum-manganese master alloy, pure antimony, pure zinc, etc. in an oven to 160°C, and simultaneously Occupy the purpose alloy total weight 2wt% ½ RJ-2 covering agent (the manufacturer of RJ-2 covering agent is Sichuan Lande Hi-Tech Industry Co., Ltd., and its brand name is ZS-MF1) is put into baking oven; Preheat to 30CTC in a box-type furnace.

2) When the temperature of the crucible rises to 300°C, inject _CO2 gas into the crucible for gas replacement, then add about 1/2 of the baked covering agent to the bottom of the crucible, and then mix the preheated pure magnesium Put it in the crucible.

3) After the pure magnesium ingredients are melted and the temperature of the crucible is stabilized at 720°C, add various preheated ingredients (pure aluminum, aluminum-manganese intermediate alloy, pure antimony, pure zinc, etc.) in order according to the melting point from high to low, and then melt Stir the body for about 8 to 10 minutes; during this process, add the remaining baked covering agent as appropriate, subject to the fact that the surface is non-combustible.

4) After the temperature of the crucible is stabilized at 72CTC, the melt is left to stand for 4 minutes, and the slag is removed under the protection of 99~99.5% air (or C0 ₂ )+0.5~1% SF ₆ mixed gas according to the volume percentage;

5) After the slagging is completed, keep the temperature of the crucible at 720°C, and cast it under the protection of 99~99.5% air (or C0 ₂ ) + 0.5-1% SF ₆ mixed gas according to the volume percentage.

The smelting and casting processes of AZ91 and AM60 alloys are similar to those of AZY641, except that the addition of various alloying elements is different.

ΠΙ), alloy heat treatment:

The heat treatment of the three alloys can be divided into three types: T4 (solution), T5 (aging), and T6 (solution + aging): a) T4 heat treatment: The T4 heat treatment temperature can be deduced from the differential thermal analysis (DTA) data of the alloy. For example (refer to FIG. 3), the DTA curve of the alloy of Example 1 shows that there are two inflection points near the solidus (377 ° C,

354°C). According to experiments, the T4 heat treatment of the alloy in Example 1 cannot exceed 1370°C. The T4 heat treatment temperature of the alloy of Example 1 was 370°C, and the time was 12 hours. The T4 heat treatment temperature of AZ91 and AM60 alloys is 410°C, and the heat treatment time is controlled at 16-24 hours. The samples after T4 heat treatment were all air-cooled to room temperature.

b) T5 heat treatment: The three alloys can adopt the same T5 heat treatment. The temperature of T5 heat treatment was controlled at 180°C, and the temperature of T5 heat treatment was 16 hours, and the samples after heat treatment were all cooled to room temperature in air.

c) T6 heat treatment: T6 heat treatment can be regarded as a combination of T4 and T5 heat treatment. Each alloy has its respective appropriate T4 and T5 heat treatments described successively.

IV), auditory tissue representation,

«The sample preparation process for tissue observation is as follows: Use No. 1000 silicon carbide water abrasive paper to smooth the surface; then use an oil-based diamond grinding paste machine to leak light; the polished sample surface is etched with 2% concentration of nitric acid alcohol solution. Surface structure observation was carried out on a Philips XL30 ESEM-FEG/EDAX equipped with a scanning electron microscope equipped with an energy spectrum device.

Compared with the alloy without adding antimony elements, the as-cast structure of the alloy of Example 1 has a certain degree of refinement of primary crystal grains and secondary precipitated phases (refer to FIG. 4 ). The mechanism of this process can be understood as follows: A small amount of antimony element will form MS particles with a melting point of 1228°C with magnesium; these ?^ 81¾ particles will be preferentially formed during the cooling process of the melt, and some of the particles will become primary phases The heterogeneous nucleation centers of the sintered phase refine the primary phase; other _Mg3Sb2 particles will appear in the growing liquid phase front to interact with the precipitation of the secondary phase, resulting in a more diffuse distribution of the secondary precipitated phase. In scanning electron microscopy and energy spectrum observation, Mg3Sb ₂ particles not only appear inside the primary crystal grains, but also appear on the grain boundaries (refer to Figure 5).

Figure 6 and Figure 7 show the microstructure evolution of the alloy of Example 1 caused by different heat treatment methods. It can be seen from Figure 6 that most of the secondary precipitated phases were re-dissolved into the primary phase after the T4 heat treatment, and the remaining particles in the figure are all particles with high melting points (such as MfeSbz and Al-Mn^ particles, etc.). T6 heat treatment causes the solute elements to re-precipitate from the primary grains and distribute in the grain boundaries and inside the grains in a more dispersed form (refer to Figure 7).

V ), mechanical performance test

The room temperature mechanical tensile properties of the alloy samples were prepared according to the Chinese national standard GB 6397-86. The parallel distance dimension of the sample is 30 X 6 X 3 (mm). The surface of the samples was polished with 1000-grit silicon carbide sandpaper. The strain rate for the tensile test was 1.11 X 1θΎ.

• High temperature (150°C) mechanical tensile properties of the alloy. The parallel distance of the sample is 27X 5 X3 (mm). The surface of the sample was polished with 1000 grit silicon carbide sandpaper. The strain rate of the tensile test is 5.55X 10 ⁴ S ⁴ . The Brinell hardness sample preparation and experimental method of the alloy refer to GB231-84, and the sample size is 15x15x5 (mm) _0. The impact performance sample of the alloy is prepared according to the Chinese national standard GB T 229-1994. The parallel distance dimension of the sample is 10x10x55

(mm), the sample is an unnotched sample.

Figure 8 shows the comparison of mechanical properties at room temperature of as-cast alloys (AZ91-F, AM60-F, Example 1-F). Figure 9 shows the comparison of mechanical properties at room temperature of T6 heat-treated alloys (AZ91-T6, AM60-T6. Example 1-T6). Example 1. Room temperature mechanical properties of the alloy: Yield strength, tensile strength, elongation, impact energy, heat treatment state, Brinell hardness

(MPa) (MPa) (%) (J) as-cast 216 106 . 10 60 19

T4 heat treatment 250 101 12 59 30

T5 heat treatment 230 128 7 65 12

T6 heat treatment 285 137 8.5 68 18 It can be seen from Table 3 that T4 heat treatment improves the plasticity of the alloy in Example 1; T5 heat treatment also improves the mechanical properties to a certain extent. T6 heat treatment gives the highest yield strength and tensile strength, but sacrifices some plasticity compared with T4 heat treatment.

The comparison of the mechanical properties of Example 1 and AZ91 alloy at room temperature is shown in Figure 10, and the comparison of the high temperature mechanical properties of Example 1 and AZ91 alloy is shown in Figure 11. It can be seen that although the comprehensive mechanical properties at room temperature of Example 1 are better than those of AZ91, the mechanical properties at high temperatures are slightly inferior to those of AZ91.

Example 2

I ), alloy composition

The chemical composition of the alloy in Example 2 is shown in Table 4. Table 4. The chemical composition table of the alloy of embodiment 2 (weight percentage wt %)

Example 2 6.16 5.08 0.31 0.48 Balance margin

II ), alloy smelting and casting

Referring to the smelting and casting of Example 1. Here's the difference: Both have different levels of zinc.

ΠΙ), alloy heat treatment: Refer to the heat treatment of Example 1. The difference is that: according to the DTA data of the alloy of Example 2, the temperature of the solution heat treatment is 360°C, and the time is 12 hours; the temperature of the aging treatment is 180°C, and the time is 16 hours.

IV), mechanical property test

Refer to the mechanical property test of Example 1. Table 5. Mechanical properties of the alloy in Example 2 at room temperature Yield strength Tensile strength Elongation Impact energy Heat treatment state Brinell hardness

(MPa) (MPa) (%) (J) As cast 110 210 8 63 15

T6 heat treatment 145 250 6.74 12 The comparison of the high temperature mechanical properties of Example 2 and AZ91 alloy is shown in Figure 11. It can be seen that Example 2 not only has better comprehensive mechanical properties at room temperature than AZ91, but also has better high temperature mechanical properties than AZ91.

Example 3

I), alloy composition

The chemical composition of the alloy in Example 3 is shown in Table 6. Table 6. Chemical balance of the alloy in Example 3 (wt %) Alloy Aluminum Zinc Manganese Magnesium Example 3 5.89 6.74 0.35 0.53 Balance balance

II ), alloy smelting and casting

Referring to the smelting and casting of Example 1. Here's the difference: Both have different levels of zinc.

III), alloy heat treatment:

Refer to the heat treatment of Example 1. The difference is: according to the DTA data of the alloy of Example 3, the temperature of the solution heat treatment is 350°C, and the time is 12 hours; the temperature of the aging treatment is 180°C, and the time is 16 hours.

IV) , mechanical property test

Refer to the mechanical property test of Example 1. Table 7. Mechanical properties of the alloy in Example 3 at room temperature Heat treatment state Yield strength Tensile strength Elongation Brinell hardness Impact energy (MPa) (MPa) (%) (J) As cast 115 202 6.5 67 13

T6 heat treatment 153 260 5 77 9 The comparison of the high temperature mechanical properties of Example 3 and AZ91 alloy is shown in Figure 11. It can be seen that not only the comprehensive mechanical properties at room temperature of Example 3 are higher than those of AZ91, but also the strength properties of high temperature mechanical properties are better than those of AZ91.

Example 4

I ), alloy composition

The chemical composition of the alloy in Example 4 is shown in Table 8.

28. The chemical stripping of embodiment 4 alloy (percentage by weight wt %)

Ce-rich mix

Aluminum Zinc Manganese

rare earth

Example 4 6.00 3.79 0.54 0.50 0.90 Balance margin

II ), alloy smelting and casting

Referring to the smelting and casting of Example 1. The difference is that: the alloy of embodiment 4 adds a small amount of cerium-rich mixed rare earth on the basis of the alloy of embodiment 1.

Since the melting point of the misch metal is relatively high, when adding the ingredients, the cerium-rich misch metal should be added first, and it is best to add the misch metal when the melt temperature in the crucible is 750-800°C.

III), the heat treatment of alloy:

Refer to the heat treatment of Example 1. The difference is that: according to the DTA data of the alloy in Example 4, the solution treatment temperature of the alloy is 370°C, and the time is 12 hours; the temperature of the aging treatment is 180°C, and the time is 16 hours.

IV) 、 Mechanical performance test

Refer to the mechanical property test of Example 1. Example 4 The room temperature mechanical properties of the alloy Yield strength Tensile strength Elongation Impact energy Heat treatment state Brinell hardness

(MPa) (MPa) (%) (J) Prayer 111 230 10 64 19

T6 heat treatment 146 272 8.7 77 13 The comparison of the high temperature mechanical properties of Example 4 and AZ91 alloy is shown in Figure 12. It can be seen that although the comprehensive mechanical properties at room temperature of Example 1 are better than those of AZ91, the high temperature mechanical properties are slightly inferior to those of AZ91.

Example 5

I ), alloy composition

The chemical composition of the alloy in Example 5 is shown in Table 10. Table 10. Chemical composition of the alloy of Example 5 (weight percent wt %)

Ce-rich mix

Alloy Aluminum Zinc Manganese

rare earth

Example 5 4.77 5.59 0.42 0.45 0.49 Balance margin

II ), alloy smelting and casting

Referring to the smelting and casting of Example 1. The difference is: refer to the smelting and casting of Example 1. The difference is that, in addition to the different contents of aluminum and zinc, a small amount of cerium-rich mixed rare earth is added to the alloy of Example 5.

Since the melting point of the misch metal is relatively high, when adding the ingredients, the cerium-rich misch metal should be added first, and it is best to add the misch metal when the melt temperature in the crucible is 750-800°C.

III), alloy heat treatment:

Refer to the heat treatment of Example 1. The difference is that: according to the DTA data of the alloy in Example 5, the solution treatment temperature of the alloy is 350°C, and the time is 12 hours; the temperature of the aging treatment is 180°C, and the time is 16 hours.

W Mechanical property test

Refer to the mechanical property test of Example 1. Table 11 Room temperature mechanical properties of Example 5 alloy Yield strength Tensile strength Elongation Impact energy Heat treatment state Brinell hardness

(MPa) (MPa) (%) (J) As cast 115 210 7.4 68 15

T6 heat treatment 156 282 7.0 79 12 The comparison of the high temperature mechanical properties of Example 5 and AZ91 alloy is shown in Figure 12. It can be seen that Example 5 is not only better than AZ91 in comprehensive mechanical properties at room temperature, but also better than AZ91 in strength properties of high temperature mechanical properties.

Claims (1)

1. Claim

   1st, a kind of high-intensity high-tenacity cast magnesium alloy, it is characterised in that：By weight percentage, the essential element composition for alloying is as follows：Aluminium content is 3 ~ 9%；Zn content is 3.5 ~ 9%；Manganese content is 0.15 ~ 1.0%；Antimony content is 0.01-2%；Content of magnesium is balance.

   2nd, ^^ gold is cast according to the high just property of the high intensity described in claim 1, it is characterised in that：Households M antimony powders can be technical pure antimony, and its purity is 99.7%.

   3rd, ^^ gold is cast according to the high Wei Ren of high intensity described in claim 1, it is characterised in that：0 ~ 2 wt% cerium-rich mischmetal, calcium, certain element of silicon thrin can also further be contained in alloy.

   4th, the preparation method of ^ ^ gold is cast according to the high-intensity high-tenacity described in claim 1, it is characterised in that its melting and as follows around note process： . .

   1) crucible target temperature is first set as 700 ~ 750 °C, is begun to warm up；Then various dispensings are put and is preheated to 140 ~ 200 °C in an oven, and the coverture for accounting for purpose alloy gross weight 0.64% is put into baking in baking oven；In addition, casting is preheated into 20 (00 °C with mould in other batch-type furnace；

   2) when crucible is warming up to 280 ~ 320 °C, it is passed through C0₂Gas displacement is carried out in gas to crucible, the Λ 30% 50% above-mentioned coverture toasted is then added in crucible bottom, then afterwards by preheated pure magnesium dispensing side crucible；

   3) pure magnesium dispensing melts and waits crucible temperature stable after 700 ~ 750 °C, sequentially adds the various dispensings of preheating from high to low according to fusing point, then melt is stirred 8 ~ 10 minutes；During this, the remaining coverture toasted is added, is defined so that surface is non-ignitable；

   4) crucible temperature is stable after 700 ~ 750 °C, and melt stands 4 ~ 6 minutes, by percent by volume, in 99 99.5% air or C0₂+ 0.5-1% SF₆Surface scum is drawn out under mixed body protection；

   5) draw after slag finishes, crucible temperature is maintained at 700 ~ 750 °C, by percent by volume, in 99 ~ 99.5% air or C0₂+ 0.5-1% SF₆Mixed gas protected lower cast molding.

   5th, ^ Preparation Methods are closed according to the high-intensity high-tenacity casting magnesium described in claim 4, it is characterised in that：The heat treatment that alloy is used is segmented into three kinds：Solution treatment, artificial aging and solution treatment+artificial aging.

   6th, according to the preparation method of the high-intensity high-tenacity cast magnesium alloy described in claim 5, it is characterised in that：The temperature range of the solution treatment is that 34 (K400 °C, time of solution treatment is 8 ~ 24 hours.

   7th, according to the preparation method of the high Firmware cast magnesium alloys of high intensity described in claim 5, it is characterised in that：The temperature range of the artificial aging is 70 ~ 200 °C, and the time of processing is 8 ~ 24 hours.

   8th, according to the preparation method of the high-intensity high-tenacity cast magnesium alloy described in claim 5, it is characterised in that：The cast molding is prayed using metal mold makes, or using sand casting, compression casting or Extrution casting technique.