CN116005054A - Low-cost high-strength high-heat-conductivity magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a low-cost high-strength high-heat-conductivity magnesium alloy which comprises the following components in percentage by mass: 1.6-2.9% of Zn, 0.3-0.8% of Ca, 0.2-0.3% of Mn, 0-0.4% of Ce, and the balance of Mg and unavoidable impurities; the preparation method of the magnesium alloy comprises the following steps: 1. preheating; 2. smelting and casting; 3. homogenizing; 4. extruding and deforming; 5. accumulating rolling deformation; 6. and (5) low-temperature annealing treatment. The magnesium alloy adopts Zn and Ca as main alloying elements, improves the strength and plasticity of the magnesium alloy, reduces the influence of solid solution atoms on the heat conductivity of the magnesium alloy, ensures the heat conductivity of the magnesium alloy and reduces the cost of raw materials; the invention adopts extrusion and rolling combination deformation, refines the grain size of the magnesium alloy, improves the comprehensive mechanical property of the magnesium alloy, and combines short-time low-temperature annealing treatment to improve the elongation, the heat conductivity and the strength of the magnesium alloy.

Description

A low-cost, high-strength, high-thermal conductivity magnesium alloy and its preparation method

technical field

The invention belongs to the technical field of non-ferrous metal materials, and in particular relates to a low-cost, high-strength, high-thermal conductivity magnesium alloy and a preparation method thereof.

Background technique

With the rapid development of 5G communication, the power of electronic components increases rapidly. At the same time, electronic components continue to be miniaturized and lightweight, resulting in an increasing calorific value per unit volume, which affects the thermal conductivity of lightweight heat dissipation materials. And the mechanical properties put forward higher and higher requirements, and at the same time, it is necessary to ensure that the material has good plasticity and processability. Magnesium alloys have attracted extensive attention due to their low density and good thermal conductivity. The density of pure magnesium is 1.74g/cm ³ , and the thermal conductivity at room temperature is 157W/(m·K). However, the tensile strength of pure magnesium is only about 70MPa~80MPa, which is difficult to meet the strength requirements of general structural materials. On the basis of pure magnesium, adding one or more alloying elements can greatly improve the mechanical properties of magnesium alloys through fine grain strengthening, solid solution strengthening and precipitation strengthening, but the above methods will inevitably lead to a strong magnesium lattice. Distortion, thereby increasing the mean free path of electrons, and decreasing the thermal conductivity of the alloy. For example, the die-casting AZ91 alloy reported in the literature has a tensile strength of 230MPa at room temperature, a yield strength of 150MPa, and a thermal conductivity of 54W/(m K); while the extruded ZM31 alloy has a tensile strength of 321MPa, yield strength 168MPa, thermal conductivity 113MPa; aging treatment after extrusion deformation, the tensile strength of ZM31 alloy increased to 283MPa, yield strength increased to 211MPa, thermal conductivity increased to 125W/(m K) and WE54 alloy after T6 treatment, the tensile strength at room temperature can reach 250MPa, the yield strength is 172MPa, but at the same time the thermal conductivity is only 51.3W/(m·K). From the above results, it can be seen that the magnesium alloy series commonly used in the market cannot meet the performance requirements of high strength and high thermal conductivity at the same time under the traditional preparation method, so it is urgent to innovate in composition design and processing technology to obtain a High strength and high thermal conductivity magnesium alloy and its preparation process.

In recent years, some magnesium alloys with high strength and high thermal conductivity and their preparation methods have been publicly reported at home and abroad. For example, the alloy composition disclosed in the Chinese patent with publication number CN111218597B contains Zn 3.7%~4.2%, Mn 0.4%~0.5 %, Ca 0.2%~0.4%, La 0.15%~0.25%; in the hot extrusion state, the yield strength at room temperature is 180MPa~250 MPa, the tensile strength is 250MPa~320 MPa, and the elongation is 30% ~36%, thermal conductivity 130W/(m K)~140 W/(m K). However, in the case of ensuring good thermal conductivity and elongation of the alloy, the strength of the alloy is still low, which cannot meet the requirements of high strength and high thermal conductivity. Publication No. CN111218595B contains Zr 0.4%-0.6%, Zn 4%-6%, and Ca 0.4%-0.8% in the alloy composition disclosed by the Chinese patent of CN111218595B; the tensile strength of the alloy is greater than 325MPa, the yield strength is greater than 280MPa, The efficiency is greater than 15%, and the thermal conductivity is greater than 120W/(m·K). However, the alloy needs to be subjected to an aging treatment of up to 30 hours, and the preparation period is long; at the same time, the alloy has a high Zn content, the alloy has poor thermal cracking resistance, and poor formability under high-speed deformation conditions.

Therefore, in order to better meet the demand for high-strength, high-thermal-conductivity lightweight alloys in the fields of electronics and automobiles, it is urgent to solve the problem that the high-strength and high-thermal conductivity of magnesium alloys are difficult to balance, and to develop new types of magnesium alloys with relatively low cost and short preparation cycles. Magnesium alloy heat dissipation material.

Contents of the invention

The technical problem to be solved by the present invention is to provide a low-cost, high-strength, high-thermal-conduction magnesium alloy for the above-mentioned deficiencies in the prior art. The alloy uses Zn and Ca as the main alloying elements, and the strength and plasticity of the magnesium alloy are improved through Zn strengthening, while the addition of Zn and Ca at the same time is conducive to the formation of a stable Ca ₂ Mg ₆ Zn ₃ phase, reducing the solid solution atoms For the thermal conductivity of the magnesium alloy, the thermal conductivity of the magnesium alloy is guaranteed, and the magnesium alloy is composed of Zn, Ca, Mn elements and a small amount of rare earth Ce, and the cost of the alloy raw material is low.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a low-cost, high-strength, high-thermal conductivity magnesium alloy, characterized in that it consists of the following components by mass percentage: Zn 1.6% ~ 2.9%, Ca 0.3% ~ 0.8%, Mn 0.2%~0.3%, Ce 0~0.4%, the rest is Mg and unavoidable impurities.

Aiming at the problems of high alloyed magnesium alloys with high strength but low thermal conductivity and elongation in existing heat-conducting magnesium alloys, and low-alloyed magnesium alloys with high thermal conductivity and elongation but insufficient strength, the magnesium alloy of the present invention By adding Zn, the strength and plasticity of the magnesium alloy are effectively improved, and at the same time, nano-scale precipitates are formed during the heat treatment of the magnesium alloy, resulting in a strengthening effect; since the atomic radius of Zn is 0.139 μm smaller than that of Mg, and the atomic radius of Ca is 0.197 The μm is larger than that of Mg, and the negative value of the mixing enthalpy between Zn-Ca atoms is relatively large. The addition of Zn and Ca at the same time is conducive to the formation of a stable Ca ₂ Mg ₆ Zn ₃ phase, which effectively reduces the solid solution atoms when Zn and Ca are added alone. The effect on the degree of Mg lattice distortion, thereby reducing the effect of solid solution atoms on the thermal conductivity of magnesium alloys.

In the magnesium alloy of the present invention, the Fe-Mn precipitation phase is formed by adding Mn and the impurity element Fe contained in the magnesium raw material itself and introduced in the smelting process, and the corrosion behavior and elongation of the magnesium alloy are improved by reducing the Fe content, and at the same time, Mn is finely dispersed in the magnesium alloy. Crystallization is beneficial to improve the mechanical properties of magnesium alloys.

In the magnesium alloy of the present invention, the grain size is refined by adding Ce, the texture strength of the basal surface is weakened, and the non-basal surface slip is stimulated, thereby improving the elongation of the alloy; at the same time, the addition of Ce promotes the Mg-Zn-Ca three The precipitation of elemental phases reduces the influence of solid solution elements on the thermal conductivity of magnesium alloys.

The Ca, Mn and Ce elements in the magnesium alloy of the present invention have very low solid solubility in Mg at room temperature and are almost insoluble in the Mg matrix, thus having little influence on the scattering of electrons or phonons, making these alloy elements The impact on thermal conductivity is small; in addition, the simultaneous addition of Zn and Ca in the present invention will precipitate Ca ₂ Mg ₆ Zn ₃ phases from the matrix, thereby reducing the content of Zn and Ca atoms in solid solution in the matrix and improving the magnesium alloy. Thermal conductivity.

Therefore, the magnesium alloy of the present invention adopts Zn, Ca, Mn, Ce as alloying elements, adopts lower alloying element content to reduce the influence of alloying elements solid solution in the magnesium matrix on the degree of lattice distortion, and ensures that the magnesium alloy has Good thermal conductivity and plastic processing performance, while reducing the cost of raw materials; in addition, stable atomic bonding can be formed between alloying elements, and precipitated in the form of precipitates, improving the strength of magnesium alloys, and obtaining low-cost, high-strength, high-thermal conductivity magnesium alloys.

The aforementioned low-cost, high-strength, and high-thermal conductivity magnesium alloy is characterized in that it consists of the following components by mass percentage: Zn 2.0%, Ca 0.4%, Mn 0.2%, and the rest are Mg and unavoidable impurities.

In addition, the present invention also discloses a method for preparing the above-mentioned low-cost, high-strength and high-thermal conductivity magnesium alloy, which is characterized in that the method includes the following steps:

Step 1. Preheating: According to the design composition of the target magnesium alloy, mix Mg, Zn, Mg-Ca master alloy, Mg-Mn master alloy and Mg-Ce master alloy, and preheat them at 300°C~400°C for 30 minutes;

Step 2. Melting and casting: under the protection of mixed gas, place the Mg preheated in step 1 in a resistance furnace and keep it warm at 700°C~720°C until it is completely melted, and then add step 1 in sequence at 730°C~760°C Zn, Mg-Ca master alloy, Mg-Ce master alloy and Mg-Mn master alloy preheated in medium, then add refining agent at 730℃ and stir evenly to remove surface scum, keep it for 20min~40min, and then Metal mold casting or semi-continuous casting is carried out at 700℃~720℃, and alloy ingots are prepared after casting;

Step 3. Homogenization treatment: under the protection of inert gas, heat the alloy ingot obtained in step 2 at 350°C~390°C for 8h~26h, then air cool to room temperature, and remove the surface oxide layer to obtain homogenization treatment alloy ingot;

Step 4. Extrusion deformation: preheat the homogenized alloy ingot obtained in step 3 at 330°C~380°C for 2 hours, and then extrude through the extrusion die at a speed of 0.1m/min~5m/min And extrude and air-cool to room temperature to obtain an extruded magnesium alloy plate;

Step 5, accumulative rolling deformation: preheat the extruded magnesium alloy sheet obtained in step 4 at 300°C~350°C for 30min, then roll at a rolling speed of 10m/min~30m/min and water-cool to room temperature, Obtain magnesium alloy plate;

Step 6, low-temperature annealing treatment: heat the magnesium alloy plate obtained in step 5 at 250° C. for 5 minutes to 20 minutes and water-cool to room temperature to obtain a low-cost, high-strength and high-thermal conductivity magnesium alloy.

The invention preheats the raw materials of the magnesium alloy so that the raw materials are fully dried, avoiding the reaction of the moisture in the raw materials with the Mg solution and even splashing to affect the smelting process, and at the same time reducing the temperature difference between other raw materials and the Mg solution formed by heat preservation and melting. Avoid burning on the surface when other raw materials are added due to large temperature differences, and then formulate the order of adding raw materials in turn according to the melting point and burning loss rate of each raw material alloy: usually the raw material alloy with low burning loss rate and lower melting point has a lower temperature in the Mg melt When the raw material alloy with high burning loss rate and high melting point is added when the Mg melt temperature is high or when the casting time is short, the burning loss of the raw material alloy can be effectively reduced, and then the refining agent is added to smelt and cast to obtain Alloy ingot: Homogenize the alloy ingot to reduce the segregation of solute elements in the alloy ingot, and at the same time dissolve part of the second phase back into the matrix, improving the formability of the alloy in the subsequent deformation process; and then sequentially Extrusion deformation and rolling deformation are carried out to further refine the grain size and improve the mechanical properties of magnesium alloys, and low-temperature annealing is carried out after rolling to obtain magnesium alloys, which promotes the occurrence of microstructure recovery in magnesium alloys, thereby reducing the The dislocation density improves the elongation and thermal conductivity of the magnesium alloy.

The above method is characterized in that the mixed gas in step 2 includes SF ₆ with a volume fraction of 0.1%-1%, and CO ₂ or N ₂ with a volume fraction of 99%-99.9%. A small amount of SF6 in the mixed gas of the present invention prevents the combustion of molten magnesium and protects the smooth progress of the magnesium alloy smelting process, while the _CO2 or _N2 gas that accounts for a large volume fraction plays the role of carrying current.

The above method is characterized in that the inert gas in step 3 is _N2 or Ar.

The above method is characterized in that the extrusion ratio used in the extrusion in step 4 is 16-32. By controlling the extrusion ratio, the strain energy is reduced, which ensures the effect of grain refinement, and at the same time avoids excessive pressure ratio, large extrusion force required for deformation, and increased friction during extrusion deformation, resulting in heat generation The increase, on the contrary, causes the crystal grains to grow due to the recovery phenomenon.

The above-mentioned method is characterized in that the cumulative reduction of the rolling described in step five is 60%-90%, the reduction of a single pass is 15%-30%, and after each pass is rolled at 300°C ~350°C heat preservation for 3 minutes and then the next rolling pass. Due to the good heat dissipation performance of magnesium alloy, the temperature drop of the plate is very fast during the rolling deformation process, resulting in the cracking of the plate during the rolling process. Therefore, in the multi-pass rolling process, it is necessary to re- Return to the furnace for heat preservation to ensure that the temperature of the rolled plate is within the predetermined rolling temperature range and ensure the smooth progress of rolling.

Compared with the prior art, the present invention has the following advantages:

1. The magnesium alloy of the present invention uses Zn and Ca as the main alloying elements, and the strength and plasticity of the magnesium alloy are improved by adding Zn for strengthening, and the addition of Zn and Ca at the same time is conducive to the formation of a stable Ca ₂ Mg ₆ Zn ₃ phase , which effectively reduces the influence of solid solution atoms Zn and Ca on the degree of Mg lattice distortion when added alone, thereby reducing the influence of solid solution atoms on the thermal conductivity of magnesium alloys, ensuring the thermal conductivity of magnesium alloys, and magnesium alloys It is composed of Zn, Ca, Mn elements and a small amount of rare earth Ce, and the cost of alloy raw materials is low.

2. In the magnesium alloy of the present invention, by adding Mn and Ce to refine the grain size, the mechanical properties of the magnesium alloy are improved, and at the same time, the precipitation of the Ca ₂ Mg _{6 Zn} ternary phase is promoted, which reduces the impact on the thermal conductivity of the magnesium alloy. Influence.

3. The preparation method of the present invention refines the grain size of the magnesium alloy and improves the comprehensive mechanical properties of the magnesium alloy by adopting the combined deformation of extrusion and rolling; after rolling, low-temperature annealing treatment is carried out to promote the microstructure of the magnesium alloy. The recovery occurs, thereby reducing the dislocation density in the structure and improving the elongation and thermal conductivity of the magnesium alloy. At the same time, the short-time annealing treatment ensures that the grains do not grow too much during the annealing process, thereby ensuring that the magnesium alloy remains Has a higher strength.

4. The plastic deformation processes such as extrusion and rolling involved in the preparation method of the present invention can be completed by general-purpose equipment, without the need for special transformation of the equipment, which reduces the additional preparation cost of transformation, and does not include long-term processing in the present invention. aging treatment, thereby reducing the preparation period and improving the production efficiency of the magnesium alloy.

5. By controlling the composition of the magnesium alloy and the preparation process of the magnesium alloy, the present invention effectively refines the crystal grains and obtains precipitated phases, reduces the influence on the thermal conductivity of the magnesium alloy while improving the strength of the magnesium alloy, and obtains a yield strength greater than 250MPa, High strength and high thermal conductivity magnesium alloy with tensile strength greater than 270MPa, elongation greater than 10%, and thermal conductivity at room temperature above 120W/(m·K).

The technical solutions of the present invention will be described in further detail below with reference to the drawings and embodiments.

Description of drawings

Fig. 1 is a flow chart of the preparation method of the low-cost, high-strength and high-thermal conductivity magnesium alloy of the present invention.

Fig. 2 is a microstructure diagram of the low-cost, high-strength and high-thermal conductivity magnesium alloy prepared in Example 3 of the present invention.

FIG. 3 is a microstructure diagram of the magnesium alloy prepared in Comparative Example 1 of the present invention.

FIG. 4 is a microstructure diagram of the magnesium alloy prepared in Comparative Example 2 of the present invention.

Fig. 5 is a graph showing tensile stress-strain curves of the low-cost, high-strength, high-thermal conductivity magnesium alloy prepared in Example 3 of the present invention and the magnesium alloy prepared in Comparative Examples 1-2.

Detailed ways

Example 1

The low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment is composed of the following components by mass percentage: Zn 1.6%, Ca 0.3%, Mn 0.2%, Ce 0.2%, and the rest is Mg and unavoidable impurities.

As shown in Figure 1, the preparation method of the low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment includes the following steps:

Step 1. Preheating: According to the design composition of the target magnesium alloy, Mg ingot with a mass purity of 99.99%, Zn ingot with a mass purity of 99.99%, Mg-30%Ca master alloy, Mg-5%Mn master alloy and Mg-30% The Ce master alloy is batched and placed in a resistance furnace for preheating at 300°C for 30 minutes;

Step 2, smelting and casting: under the protection of a mixed gas composed of 0.1% SF ₆ and 99.9% N ₂ by volume fraction, place the preheated Mg ingot in step 1 in a resistance furnace at 700 Keep warm at ℃ until completely melted, raise the temperature of the melt to 730℃, add the preheated Zn ingot and Mg-30%Ca master alloy in step 1 in sequence and keep warm until completely melted, then raise the temperature of the melt to 750℃, Add the preheated Mg-5%Mn master alloy and Mg-30%Ce master alloy in step 1 and keep it warm until completely melted, then lower the temperature to 730°C and add RJ-5 refining agent with 1% of the melt mass to evenly stir and remove The surface scum was left to stand for 20 minutes, and then semi-continuous casting was carried out at 700°C, and alloy ingots were prepared after casting;

Step 3, homogenization treatment: under the protection of Ar atmosphere, heat the alloy ingot obtained in step 2 at 390° C. for 8 hours, then air-cool to room temperature, and remove the surface oxide layer to obtain the alloy ingot after homogenization treatment;

Step 4, extrusion deformation: preheat the homogenized alloy ingot obtained in step 3 at 380° C. for 2 hours, and then extrude through an extrusion die at a speed of 5 m/min and an extrusion ratio of 32, And extrude and air-cool to room temperature to obtain an extruded magnesium alloy plate with a thickness of 5mm;

Step 5, cumulative rolling deformation: preheat the extruded magnesium alloy sheet obtained in step 4 at 350°C for 30 minutes, then roll at a rolling speed of 30m/min and water-cool to room temperature. The weight is 90%, the single-pass reduction is 20%, and after each rolling pass, it is kept at 350°C for 3 minutes before the next rolling pass to obtain a magnesium alloy plate with a thickness of 0.5mm;

Step 6. Low-temperature annealing treatment: heat the magnesium alloy sheet obtained in Step 5 at 250° C. for 5 minutes and water-cool to room temperature to obtain a low-cost, high-strength, high-thermal conductivity magnesium alloy.

Example 2

The low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment is composed of the following components by mass percentage: Zn 2.9%, Ca 0.8%, Mn 0.3%, Ce 0.4%, and the rest is Mg and unavoidable impurities.

As shown in Figure 1, the preparation method of the low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment includes the following steps:

Step 1. Preheating: According to the design composition of the target magnesium alloy, Mg ingot with a mass purity of 99.99%, Zn ingot with a mass purity of 99.99%, Mg-30%Ca master alloy, Mg-5%Mn master alloy and Mg-30% The Ce master alloy is batched and placed in a resistance furnace for preheating at 350°C for 30 minutes;

Step 2, smelting and casting: under the protection of a mixed gas composed of 1% SF ₆ and 99% CO ₂ by volume fraction, place the preheated Mg ingot in step 1 in a resistance furnace at 700 Keep warm at ℃ until completely melted, raise the temperature of the melt to 740℃, add the preheated Zn ingot and Mg-30%Ca master alloy in step 1 in sequence and keep warm until completely melted, then raise the temperature of the melt to 760℃, Add the preheated Mg-5%Mn master alloy and Mg-30%Ce master alloy in step 1 and keep it warm until completely melted, then lower the temperature to 730°C and add RJ-5 refining agent with 1% of the melt mass to evenly stir and remove The scum on the surface is left to stand for 40 minutes and then cooled to 720°C, poured into a steel mold for metal mold casting, and the alloy ingot is prepared after casting;

Step 3, homogenization treatment: under the protection of Ar atmosphere, place the alloy ingot obtained in step 2 in a tube furnace and keep it warm at 350°C for 26 hours, then air-cool to room temperature, and remove the surface oxide layer to obtain homogenization treatment After the alloy ingot;

Step 4. Extrusion deformation: preheat the homogenized alloy ingot obtained in step 3 at 330°C for 2 hours, and then extrude it through an extrusion die at a speed of 0.1m/min and an extrusion ratio of 16 , and extruded and air-cooled to room temperature to obtain an extruded magnesium alloy plate with a thickness of 5 mm;

Step 5, cumulative rolling deformation: preheat the extruded magnesium alloy sheet obtained in step 4 at 300°C for 30 minutes, then roll at a rolling speed of 10m/min and water-cool to room temperature, the cumulative rolling reduction The amount is 60%, and the single-pass reduction is 15%, and after each pass is rolled, it is kept at 300°C for 3 minutes before the next pass is rolled to obtain a magnesium alloy plate with a thickness of 2mm;

Step 6, low-temperature annealing treatment: heat the magnesium alloy sheet obtained in step 5 at 250° C. for 20 minutes and water-cool to room temperature to obtain a low-cost, high-strength, high-thermal conductivity magnesium alloy.

Example 3

The low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment is composed of the following components by mass percentage: Zn 2.0%, Ca 0.4%, Mn 0.2%, and the rest is Mg and unavoidable impurities.

As shown in Figure 1, the preparation method of the low-cost, high-strength and high-thermal conductivity magnesium alloy of this embodiment includes the following steps:

Step 1. Preheating: According to the design composition of the target magnesium alloy, Mg ingots with a mass purity of 99.99%, Zn ingots with a mass purity of 99.99%, Mg-30%Ca master alloy, and Mg-5%Mn master alloy are batched, and mixed Place in a resistance furnace and preheat at 350°C for 30 minutes;

Step 2, smelting and casting: under the protection of a mixed gas composed of 1% SF ₆ and 99% N ₂ by volume fraction, place the preheated Mg ingot in step 1 in a resistance furnace at 700 Keep warm at ℃ until completely melted, raise the temperature of the melt to 740℃, add the Zn ingot preheated in step 1, Mg-30%Ca master alloy in turn and keep warm until completely melted, then raise the temperature of the melt to 750℃, Add the preheated Mg-5%Mn master alloy in step 1 and keep it warm until it is completely melted, then lower the temperature to 730°C and add RJ-5 refining agent with 1% of the melt mass to stir evenly and remove the surface scum, and let it stand for 30 minutes After cooling down to 710°C, pour it into a steel mold for metal mold casting, and prepare an alloy ingot with a diameter of 60mm after casting;

Step 3. Homogenization treatment: under the protection of _N2 atmosphere, heat the alloy ingot obtained in step 2 at 380°C for 20 hours, then air-cool to room temperature, and remove the surface oxide layer to obtain the alloy ingot after homogenization treatment ;

Step 4. Extrusion deformation: preheat the homogenized alloy ingot obtained in step 3 at 350°C for 2 hours, and then extrude it through an extrusion die at a speed of 0.2m/min and an extrusion ratio of 20 , and extruded and air-cooled to room temperature to obtain an extruded magnesium alloy plate with a thickness of 5 mm;

Step 5, cumulative rolling deformation: preheat the extruded magnesium alloy sheet obtained in step 4 at 320°C for 30 minutes, then roll at a rolling speed of 20m/min and water-cool to room temperature, the cumulative rolling reduction The weight is 80%, the single-pass reduction is 20%, and after each rolling pass, it is kept at 320°C for 3 minutes before the next rolling pass to obtain a magnesium alloy plate with a thickness of 1mm;

Step 6, low-temperature annealing treatment: heat the magnesium alloy sheet obtained in step 5 at 250° C. for 10 minutes and water-cool to room temperature to obtain a low-cost, high-strength, high-thermal conductivity magnesium alloy.

Figure 2 is a microstructure diagram of the low-cost, high-strength, high-thermal conductivity magnesium alloy prepared in this example. Significant recrystallization occurs, making the magnesium alloy have both good strength and elongation.

Comparative example 1

The difference between this comparative example and Example 3 is that step 5 and step 6 are not carried out in the preparation method, and the extruded magnesium alloy plate obtained in step 4 is used as the product magnesium alloy.

FIG. 3 is a microstructure diagram of the magnesium alloy prepared in this comparative example. It can be seen from FIG. 3 that the metallographic structure of the magnesium alloy is a large number of recrystallized equiaxed grains.

Comparative example 2

The difference between this comparative example and Example 3 is that step 6 is not performed in the preparation method, and the magnesium alloy plate obtained in step 5 is used as the product magnesium alloy.

Figure 4 is the microstructure diagram of the magnesium alloy prepared in this comparative example. It can be seen from Figure 4 that the metallographic structure of the magnesium alloy is mainly composed of deformed grains. Compared with the magnesium alloy of Example 3, the crystal grains have a larger average grain size.

Comparative example 3

The difference between this comparative example and Example 3 is that the magnesium alloy is composed of the following mass percentages: Zn5.6%, Ca 0.4%, Mn 0.2%, and the rest are Mg and unavoidable impurities

The alloy ingot in Step 4 of the preparation process of this comparative example had obvious hot cracks during the extrusion process, and no testable extruded magnesium alloy sheet could be obtained.

The mechanical properties and thermal conductivity of the low-cost, high-strength and high-thermal conductivity magnesium alloys prepared in Examples 1 to 3 of the present invention and the magnesium alloys prepared in Comparative Examples 1 to 3 were tested, and the results are shown in Figure 5 and Table 1 below.

Combining Table 1 and Figure 5, it can be seen that compared with the magnesium alloy prepared by extrusion deformation in Comparative Example 1, it has the characteristics of high thermal conductivity but low strength, and the magnesium alloy prepared by extrusion combined with rolling deformation in Comparative Example 2 With high strength but low thermal conductivity, the magnesium alloys prepared in Examples 1 to 3 of the present invention all have the characteristics of high strength and high thermal conductivity simultaneously; meanwhile, combining Example 3 and Comparative Examples 1 to 2 By comparison, and in conjunction with Fig. 2 to Fig. 4, it can be known that the present invention adopts the process of extruding first and then rolling combined with low-temperature annealing treatment to effectively adjust the refined grain size, reduce the dislocation density, and improve the lightness of the magnesium alloy at the same time The thermal conductivity of the magnesium alloy is improved; comparing Example 3 with Comparative Example 3, it can be seen that the magnesium alloy of the present invention adopts a lower Zn content, which ensures that the alloy has good formability.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the invention still belong to the protection scope of the technical solution of the invention.

Claims (7)

1. The magnesium alloy with low cost, high strength and high heat conductivity is characterized by comprising the following components in percentage by mass: 1.6-2.9% of Zn, 0.3-0.8% of Ca, 0.2-0.3% of Mn, 0-0.4% of Ce, and the balance of Mg and unavoidable impurities.

2. The low-cost high-strength high-heat-conductivity magnesium alloy according to claim 1, which is characterized by comprising the following components in percentage by mass: zn 2.0%, ca0.4%, mn0.2%, and Mg as the rest.

3. A method of making the low cost, high strength, high thermal conductivity magnesium alloy of claim 1 or 2, comprising the steps of:

step one, preheating: according to the design components of the target magnesium alloy, mg, zn, mg-Ca intermediate alloy, mg-Mn intermediate alloy and Mg-Ce intermediate alloy are proportioned and preheated for 30min at 300-400 ℃;

step two, smelting and casting: under the protection of mixed gas, placing the Mg preheated in the step one into a resistance furnace, keeping the temperature at 700-720 ℃ until the Mg is completely melted, sequentially adding the Zn, the Mg-Ca intermediate alloy, the Mg-Ce intermediate alloy and the Mg-Mn intermediate alloy preheated in the step one at 730-760 ℃, adding a refining agent, uniformly stirring and removing surface scum, standing and keeping the temperature for 20-40 min, casting by a metal mold or semi-continuous casting at 700-720 ℃, and casting to prepare an alloy cast ingot;

step three, homogenizing: under the protection of inert gas, preserving heat for 8-26 hours at 350-390 ℃ for the alloy ingot obtained in the second step, then air-cooling to room temperature, and removing a surface oxide layer to obtain the homogenized alloy ingot;

step four, extrusion deformation: preheating the homogenized alloy cast ingot obtained in the step three at 330-380 ℃ for 2 hours, extruding at a speed of 0.1-5 m/min through an extrusion die, extruding and air-cooling to room temperature to obtain an extruded magnesium alloy plate;

step five, accumulating rolling deformation: preheating the extruded magnesium alloy plate obtained in the step four at 300-350 ℃ for 30min, rolling at a rolling speed of 10-30 m/min, and cooling to room temperature by water to obtain a magnesium alloy plate;

step six, low-temperature annealing treatment: and (3) preserving heat for 5-20 min at the temperature of 250 ℃ and cooling the magnesium alloy plate obtained in the step (V) to room temperature by water to obtain the low-cost high-strength high-heat-conductivity magnesium alloy.

4. The method according to claim 3, wherein the mixed gas in the second step includes SF having a volume fraction of 0.1% -1% ₆ And CO with the volume fraction of 99% -99.9% ₂ Or N ₂ 。

5. The method according to claim 3, wherein the inert gas in step three is N ₂ Or Ar.

6. The method according to claim 3, wherein the extrusion ratio used in the extrusion in the fourth step is 16 to 32.

7. A method according to claim 3, wherein the rolling in the fifth step has a cumulative rolling reduction of 60% -90%, a single rolling reduction of 15% -30%, and each rolling pass is followed by a 3min incubation at 300 ℃ -350 ℃ for a subsequent rolling pass.

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