WO2020062874A1 - High-thermal conductivity high-strength magnesium alloy material and preparation method therefor - Google Patents

Abstract

The present application discloses a high-thermal conductivity high-strength magnesium alloy material and a preparation method therefor. The magnesium alloy material consists of the following components in percentage by weight: 1.6-1.8 wt% of Zn, 0.4-0.9 wt% of Mn, 0.2-0.7 wt% of Y, and less than 0.2 wt% of impurities, the balance being Mg. Said method comprises ingot casting, homogenizing annealing treatment, pressing molding, and solution treating and ageing. The magnesium alloy material alloy of the present invention has a few alloy components other than magnesium added therein, resulting in low costs; the magnesium alloy material alloy of the present invention, after pressing and heat treatment, has thermal conductivity being 130 W/m.K or more at room temperature, meeting the requirements of engineering materials for thermal conductivity, and has tensile strength being 250 MPa or more, meeting the requirements of mechanical properties of magnesium alloy use.

Description

High thermal conductivity and high strength and toughness magnesium alloy material and preparation method thereof Technical field

The invention relates to the technical field of magnesium alloy materials, in particular to a high thermal conductivity, high strength and toughness magnesium alloy material and a preparation method thereof.

Background technique

China is a large country with magnesium resources, and its magnesium reserves rank first in the world. Proved magnesite reserves are 2.7 billion tons, and dolomite reserves are more than 7 billion tons. Since the popularization of China ’s independent technology Pijiang method for the extraction of magnesium, China has taken advantage of its mineral resources and coal energy advantages to become a major producer and exporter of magnesium. Annual output of more than 80% of magnesium is exported to international markets. At present, China is in the forefront of the world in terms of magnesium production capacity, magnesium production, and export volume. It is already a large country in the world for magnesium production, but it is far from being a strong country in the magnesium industry. In the field of pure magnesium production, the application fields of downstream deep-processing enterprises are not wide, especially the magnesium processing industry is still lagging behind.

Existing magnesium alloy products are difficult to ensure the smooth and smooth surface quality requirements of magnesium alloy products, and it is also difficult to meet the requirements of high strength, toughness and high thermal conductivity of complex magnesium products. The lower yield of magnesium alloys has become the production capacity and production cost of magnesium product enterprises. Major constraints. The magnesium products industry urgently hopes that China can independently research and develop and apply high-strength, high-thermal-conductivity magnesium alloys suitable for aerospace instrument housings and 3C product housings, significantly improve the yield rate of forming and the quality of magnesium products, and meet the material performance requirements of magnesium products. It has achieved significant economic benefits and can better ensure that the aerospace instrument casings produced by China and the magnesium products of 3C product casings have the innovative advantages of high surface quality and low cost in the international market, and get rid of foreign investment control.

The thermal conductivity of pure magnesium is 155W / m.K, which exceeds the thermal conductivity requirements of materials for aerospace instrument housings. However, its mechanical properties are very low and it is difficult to reach above 150MPa. By alloying and combining the corresponding process and heat treatment, the mechanical properties of the alloy can be greatly improved, but the thermal conductivity of the alloy is inevitably reduced to varying degrees. Therefore, through systematic research, it is necessary to design and develop a new high thermal conductivity, high strength and toughness magnesium alloy.

Summary of the Invention

The object of the present invention is to provide a magnesium alloy material with high thermal conductivity, high strength and toughness, and a method for preparing the same. The material is added with three elements of Zn, Mn and Y in a magnesium matrix, and has excellent thermal conductivity and mechanical properties.

The thermal conductivity of pure magnesium is 155W / m.K. Adding any element to the Mg matrix will definitely reduce the electrical conductivity and thermal conductivity of the alloy. Because alloying elements are solid-dissolved in the magnesium matrix, it will cause the lattice distortion of magnesium, which will cause wave scattering during the directional flow of free electrons, reducing the electrical conductivity and thermal conductivity of the alloy; if it is added to magnesium, the magnesium lattice distortion will be small. The element has a relatively small effect on the electrical and thermal conductivity of magnesium. After high temperature solid solution treatment, followed by deformation and aging, alloying elements are precipitated in a dispersed phase, the magnesium matrix alloy solute elements are reduced, and the strength and thermal conductivity are balanced, and the electrical conductivity and thermal conductivity of magnesium can also be improved. Therefore, the aging precipitation strengthening method is an important alloying idea for the development and preparation of high thermal conductivity magnesium alloys.

Zn element is not only an age-strengthening alloy element, but also close to the atomic radius of the Mg matrix, which causes little magnesium lattice distortion. Therefore, the thermal conductivity of Mg-Zn alloy is high. Therefore, this application chooses Mg-Zn alloy as the high thermal conductivity magnesium alloy The main alloying element is to improve the mechanical properties of the alloy as much as possible on the basis of ensuring thermal conductivity, and finally to meet the performance requirements of engineering materials. The two elements Mn and Y are added to the alloy to form a high-strength and high-toughness manganese particle and a magnesium-zinc-yttrium ternary phase, which enhances the effect of heat treatment and solid solution aging, and improves the alloy's strong toughness and heat resistance and creep resistance. Meet the mechanical properties of the alloy. In the thermal conductivity test, the alloy reached more than 135 W / m.K at room temperature and a tensile strength of more than 250 MPa, which met the requirements of engineering materials for thermal conductivity and mechanical properties. The thermal deformation heat treatment process provided by the present invention can disperse and precipitate the second phase of the alloy, reduce lattice distortion, and improve the thermal conductivity of the alloy.

The high thermal conductivity, high strength and toughness magnesium alloy material provided by the present invention is composed of the following components by weight percentage: Zn: 1.6 to 1.8 wt%; Mn: 0.4 to 0.9 wt%; Y: 0.2 to 0.7 wt%; impurities: < 0.2 wt%; the balance is Mg.

Preferably, the magnesium alloy material is composed of the following components by weight percentage: Zn: 1.6 to 1.8 wt%; Mn: 0.6 to 0.7 wt%; Y: 0.3 to 0.6 wt%; impurities: <0.2 wt%; The balance is Mg.

Preferably, the magnesium alloy material is composed of the following components by weight percentage: Zn: 1.8 wt%; Mn: 0.6 wt%; Y: 0.6 wt%; impurities: <0.2 wt%; the balance is Mg.

Preferably, the magnesium alloy material is composed of the following components by weight percentage: Zn: 1.6 wt%; Mn: 0.7 wt%; Y: 0.3 wt%; impurities: <0.2 wt%; the balance is Mg.

The preparation method of the high thermal conductivity and high strength and toughness magnesium alloy material provided by the present invention includes the following steps:

S1. Prepare a magnesium alloy ingot according to the composition of any of the magnesium alloy materials described above;

S2, the magnesium alloy ingot is homogenized and annealed at 400-450 ° C for 12-24 hours, and then the wagon is carried out;

S3. The magnesium alloy ingot after the wagon is extruded at 410 to 460 ° C, and the extrusion ratio is 20 to 30 to obtain a high thermal conductivity, high strength and toughness magnesium alloy material.

Preferably, the magnesium alloy after the extrusion molding in step S3 further includes the following solid solution and artificial aging steps to obtain a high thermal conductivity and high strength and toughness magnesium alloy material: solid solution at a temperature of 450 ° C for 3-5 hours, The temperature is 150-180 ℃ for 8-12 hours.

Preferably, step S1 is performed by a horizontal continuous casting method.

The advantages of the invention are:

1. The magnesium alloy material alloy of the present invention has less alloy components other than magnesium, and the cost is relatively low.

2. The thermal conductivity of the magnesium alloy material alloy of the present invention after extrusion and heat treatment reaches 130W / m.K or more at normal temperature, which meets the requirements for thermal conductivity of engineering materials (130W / m.K or more at normal temperature).

3. The tensile strength of the magnesium alloy material alloy of the present invention after extrusion and heat treatment is above 250 MPa, and the elongation is above 10%, which meets the requirements for the mechanical properties of magnesium alloy applications.

4. The magnesium alloy material Mg-1.8% Zn-0.6% Mn-0.6% Y provided by the present invention has outstanding thermal conductivity and mechanical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process device for preparing a magnesium alloy.

Figure 2 is the metallographic structure of two magnesium alloys after extrusion and after solution solidification aging, in which the length of the ruler in the lower right corner of each figure is 100 μm; Figures a and b represent the extrusion and extrusion solidification, respectively. Metallographic structure of magnesium alloy Mg-1.6% Zn-0.7% Mn-0.3% Y (1 #) after dissolution aging; Figures c and d represent the magnesium alloy Mg-1.8 after extrusion and extrusion solution aging, respectively % Zn-0.6% Mn-0.6% Y (2 #).

Fig. 3 shows the results of X-ray diffraction (XRD) of two magnesium alloys after extrusion solid solution aging, where a represents 1 # magnesium alloy Mg-1.6% Zn-0.7% Mn-0.3% Y, and b represents 2 # magnesium alloy Mg-1.8% Zn-0.6% Mn-0.6% Y.

detailed description

The as-cast magnesium alloys prepared in the following examples of the present invention all adopt a horizontal continuous casting process. As shown in FIG. 1, various metals of different numbered magnesium alloy compositions shown in Table 1 are first placed in a melting furnace 1 for melting. Then, it is sent to the holding furnace 3 by the pouring pump 2 and passes through the mold 4 which communicates with the holding furnace 3, and then is cooled by water shower 5 and squeezed and drawn by the double rolls 6. Finally, it is sawed by the sawing machine 7 as required.

The thermal performance test of the magnesium alloy in the following embodiments of the present invention is divided into the following steps:

(a) Density ρ: Measured in accordance with the test method for the density of precious metals and their alloys.

(b) a thermal diffusivity and specific heat capacity C _p: test alloys at room temperature, 100 ℃, 150 ℃, 200 ℃, 300 ℃ a thermal diffusivity and specific heat capacity C _p.

(c) Thermal conductivity k: Calculate k = a · ρ · C _p according to the thermal conductivity formula.

The composition of the magnesium alloy material prepared in the following examples of the present invention is shown in Table 1.

Table 1. Composition of different magnesium alloys

Numbering	Mg wt%	Zn wt%	Mn wt%	Y wt%	Impurity wt%
1#	margin	1.6	0.7	0.3	<0.2
2#	margin	1.8	0.6	0.6	<0.2

Example 1. Preparation of high thermal conductivity, high strength and toughness magnesium alloy material

Prepare a magnesium alloy ingot (magnesium alloy as-cast) according to the composition of 1 # magnesium alloy in Table 1; homogenize the magnesium alloy ingot at 400 ° C for 24 hours and perform the wagon; The ingot was extruded at 410 ° C, and the extrusion ratio was 30 to obtain an extruded magnesium alloy. The magnesium alloy was subjected to a solution treatment at a temperature of 450 ° C for 3 hours, and artificially aged at 150 ° C. After 12 hours, the solid solution aging state of the magnesium alloy after extrusion is obtained, that is, the high thermal conductivity and high strength and toughness magnesium alloy material.

Example 2: Preparation of high thermal conductivity, high strength and toughness magnesium alloy material

Prepare a magnesium alloy ingot (magnesium alloy as-cast) according to the 2 # magnesium alloy composition in Table 1. The magnesium alloy ingot is homogenized and annealed at 450 ° C for 12 hours, and then the wagon is carried out. The ingot was extruded at 460 ° C, and the extrusion ratio was 20 to obtain an extruded magnesium alloy. The magnesium alloy was subjected to a solution treatment at a temperature of 450 ° C for 5 hours, and artificially aged at 180 ° C. In 8 hours, the solid solution aging state of the magnesium alloy after extrusion is obtained, that is, the high thermal conductivity and high strength and toughness magnesium alloy material.

Comparative Example 1,

According to the alloy composition of commercial alloys AZ31, AZ61 and AZ91, magnesium alloy materials were prepared according to the method of Example 2.

Comparative Example 2,

According to the composition of the Ck1 magnesium alloy shown in Table 1-1, a control Ck1 magnesium alloy material was prepared according to the method of Example 1.

Comparative Example 3,

According to the composition of the Ck2 magnesium alloy shown in Table 1-1, a control Ck2 magnesium alloy material was prepared according to the method of Example 2.

Table 1-1. Composition of comparative magnesium alloy materials

Numbering	Mg wt%	Zn wt%	Mn wt%	Y wt%	Impurity wt%
Ck1	margin	1.5	0.7	0.3	<0.2
Ck2	margin	1.9	0.6	0.6	<0.2

result:

1. Metallographic organization chart

Figure 2 shows the results of 2 # magnesium alloy Mg-1.8% Zn-0.6% Mn-0.6% Y and 1 # magnesium alloy Mg-1.6% Zn-0.7% Mn-0.3% Y after extrusion and solid solution aging after extrusion. Microstructure.

2.X-ray diffraction (XRD)

Figure 3 shows the XRD results of magnesium alloy Mg-1.8% Zn-0.6% Mn-0.6% Y (2 #) and magnesium alloy Mg-1.6% Zn-0.7% Mn-0.3% Y (1 #), 1 #, The second phase of 2 # magnesium alloy is mainly Mg ₃ Y ₂ Zn ₃ and MgZn ₂ phases. Due to the low content of Y element in the 1 # magnesium alloy, the second-phase diffraction peak is not obvious.

As can be seen from Figures 2 and 3, when the elements of Zn and Mn are not changed, the increase of Y element makes the ternary phase of Mg ₃ Y ₂ Zn ₃ significantly increase, and the grain size decreases significantly after extrusion. , 450 ℃ solid solution can not dissolve the heat-resistant ternary phase of Mg ₃ Y ₂ Zn ₃ in the two alloys. At the same time, due to the hindrance of the ternary phase to the grain boundary movement, 450 ℃ solid solution did not significantly increase the grain Big.

3. Thermal performance

Table 2 shows the thermal properties of as-cast 1 # magnesium alloy (Mg-1.6% Zn-0.7% Mn-0.3% Y) and as-cast 2 # magnesium alloy (Mg-1.8% Zn-0.6% Mn-0.6% Y). It can be seen that the thermal conductivity of the two alloys in the as-cast condition at room temperature reaches more than 110 W / mK, and as the temperature increases, the thermal conductivity continues to increase, up to more than 130 W / mK.

Table 2. Test results of as-cast thermal properties of 1 # and 2 # magnesium alloys at different temperatures

Table 3 shows the thermal performance data of the magnesium alloy in the extruded state. It can be seen that the thermal conductivity of the two alloys in the extruded state at room temperature has slightly increased compared to the as-cast state. The thermal conductivity of the 2 # alloy has reached 120 W / mK. Above, and as the temperature increases, the thermal conductivity continues to increase, up to 147W / mK or more.

Table 3. Test results of thermal properties of 1 # and 2 # magnesium alloys in different states at different temperatures

Table 4 shows the thermal performance data of the solid solution aging state of the magnesium alloy after extrusion. It can be seen from this that the thermal conductivity of the two magnesium alloys in the heat-treated state at room temperature has a greater increase than that of the as-cast state. The thermal conductivity of the alloy reaches above 135W / mK, and with the increase of temperature, the thermal conductivity continues to increase, up to 147W / mK or higher.

Table 4. Thermal performance test results of 1 # and 2 # magnesium alloys after extrusion and solution aging

Table 5 shows the thermal conductivity of the commercial magnesium alloys AZ31, AZ61, AZ91, Ck1 and Ck2 after casting, extrusion, and extrusion + solution aging. It can be seen that the three alloys are as-cast, extruded and Compared with 1 # and 2 # magnesium alloys, the thermal conductivity during extrusion heat treatment is significantly lower, both below 100W / mK, and the increase in thermal conductivity is not obvious as the temperature increases. Compared with the 1 # and 2 # alloys, the thermal conductivity of Ck1 alloy increased slightly due to the decrease in Zn content. When the Zn element was increased to 1.9%, the thermal conductivity of Ck2 alloy decreased significantly. Extrusion + solidification at room temperature The thermal conductivity after solution aging is about 120W / mK, which can not meet the requirements of high thermal conductivity.

Table 5. Thermal conductivity (W / m · K) of as-cast, extruded, AZ31, AZ61, AZ91, Ck1 and Ck2 magnesium alloys after extrusion + solution aging

From the results in Table 2-5, it can be seen that the room temperature thermal conductivity of 1 #, 2 # and Ck1 magnesium alloys after extrusion and solution aging treatments have all reached above 135W / mK, far exceeding the current market applications. Frequent commercial alloys AZ31, AZ61 and AZ91 (below 100W / mK), and meet the requirements of engineering materials for thermal conductivity (more than 130W / mK at room temperature).

4.Mechanical properties

Table 6 shows the mechanical properties of as-cast, extruded, and 1 #, 2 #, Ck1, Ck2 magnesium alloys, and commercial alloy AZ31 after extrusion + solution aging. It can be seen that the three alloys are as-cast and extruded at room temperature. The comparison of mechanical properties in the as-expressed and heat-treated states shows that the tensile strength of 2 # alloy is the largest, and the tensile strength after extrusion + solution aging is close to 300MPa. In the design of alloys, the thermal conductivity is reduced due to the effects of alloy lattice distortion, second phase precipitation, and alloy defects. In order to improve the thermal conductivity of alloys, the alloy components other than magnesium are preferably as low as possible. Therefore, the sum of alloy components other than magnesium of 1 # and 2 # is less than 3.5%, which directly results in mechanical properties that cannot be compared with high-content magnesium alloys. In this case, the mechanical properties of alloys 1 # and 2 # It is also close to the commercial alloy AZ31, and even the tensile strength of 2 # alloy exceeds that of AZ31 alloy, which meets the market requirements for the mechanical properties of magnesium alloys (250MPa). However, due to the reduced Zn content of Ck1 alloy, the resistance after extrusion and heat treatment The tensile strength is lower than 250MPa, which does not meet the requirements for high strength of the alloy.

Table 6. Mechanical properties of as-cast, extruded, 1 #, 2 #, Ck1, Ck2 and AZ31 magnesium alloys after extrusion + solution aging

magnesium alloy	Tensile strength / MPa	Yield strength / MPa	Elongation /%
1 # As-cast	193	153	9
1 # squeezed state	252	187	13
1 # Extrusion solution aging	277	210	16
2 # As-cast	205	167	7
2 # squeezed state	268	196	12
2 # Extrusion solution aging	292	213	13
Ck1 as-cast	180	145	8
Ck1 squeezed state	241	167	12
Ck1 extrusion solution aging	246	190	15
Ck2 as-cast	214	170	5
Ck2 squeezed state	270	168	7
Ck2 extrusion solution aging	300	189	8
AZ31 as-cast	190	156	8
AZ31 squeezed state	263	201	13
AZ31 extrusion solution aging	289	227	10

The above are only examples of the present application and are not intended to limit the present application. For those skilled in the art, this application may have various modifications and changes. Any modification, equivalent replacement, and improvement made within the spirit and principle of this application shall be included in the scope of claims of this application.

Claims (7)

1. A high thermal conductivity and high strength and toughness magnesium alloy material is characterized in that the magnesium alloy material is composed of the following components in weight percentage:

   Zn: 1.6 to 1.8 wt%; Mn: 0.4 to 0.9 wt%; Y: 0.2 to 0.7 wt%; impurities: <0.2 wt%; the balance is Mg.
2. The magnesium alloy material according to claim 1, wherein the magnesium alloy material is composed of the following components by weight percentage:

   Zn: 1.6 to 1.8 wt%; Mn: 0.6 to 0.7 wt%; Y: 0.3 to 0.6 wt%; impurities: <0.2 wt%; the balance is Mg.
3. The magnesium alloy material according to claim 1 or 2, wherein the magnesium alloy material is composed of the following components by weight percentage: Zn: 1.8wt%; Mn: 0.6wt%; Y: 0.6wt% ; Impurities: <0.2wt%; the balance is Mg.
4. The magnesium alloy material according to claim 1 or 2, characterized in that the magnesium alloy material is composed of the following components by weight percentage: Zn: 1.6 wt%; Mn: 0.7 wt%; Y: 0.3 wt% ; Impurities: <0.2wt%; the balance is Mg.
5. A method for preparing a high thermal conductivity and high strength and toughness magnesium alloy material includes the following steps:

   S1. A magnesium alloy ingot is prepared according to the composition of the magnesium alloy material according to any one of claims 1-4;

   S2. The magnesium alloy ingot is homogenized and annealed at 400-450 ° C for 12-24 hours.

   S3. The magnesium alloy after homogenizing and annealing treatment is extruded at 410-460 ° C, and the extrusion ratio is 20-30, so as to obtain a magnesium alloy material with high thermal conductivity and high strength.
6. The method according to claim 5, characterized in that the magnesium alloy after the extrusion molding in step S3 further comprises the following steps of solid solution and artificial aging to obtain a high thermal conductivity, high strength and toughness magnesium alloy material: Solid solution at 450 ℃ for 3-5 hours, and aging at 150-180 ℃ for 8-12 hours.
7. The preparation method according to claim 5 or 6, wherein step S1 is performed by a horizontal continuous casting method.

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