阅读说明：本技术 一种高强度镁合金丝材及其制备方法 (High-strength magnesium alloy wire and preparation method thereof ) 是由 徐超 左静 王桂松 王晓军 施海龙 胡小石 赵德利 郭伟 耿林 于 2021-09-13 设计创作，主要内容包括：一种高强度镁合金丝材及其制备方法,涉及一种镁合金丝材及其制备方法,为了解决现有的镁合金成形性差,难以拉拔成丝的问题。丝材按质量百分比由1％～1.08％的Al、0.24％～0.3％的Ca、0.5％～0.68％的Mn和余量的Mg组成。方法：称取原料制备铸锭,均匀化退火,挤压成棒材,固溶后水冷；进行19道次的热拉拔,退火后再进行5道次热拉拔。本发明得到直径为1.6-3.8mm的丝材,塑性和韧性良好,抗拉强度达348-431MPa,屈服强度达300-394MPa,延伸率达4％-7％；拉拔过程中只进行一次中间退火,提高了镁合丝材的制备效率,降低了生产成本。本发明适用于制备高强度镁合金丝材。(A high-strength magnesium alloy wire and a preparation method thereof relate to a magnesium alloy wire and a preparation method thereof, and aim to solve the problems of poor formability and difficult wire drawing of the existing magnesium alloy. The wire consists of 1 to 1.08 percent of Al, 0.24 to 0.3 percent of Ca, 0.5 to 0.68 percent of Mn and the balance of Mg according to mass percentage. The method comprises the following steps: weighing raw materials, preparing an ingot, carrying out homogenizing annealing, extruding the ingot into a bar, and carrying out water cooling after solid solution; and carrying out 19-pass hot drawing, and carrying out 5-pass hot drawing after annealing. The invention obtains the wire with the diameter of 1.6-3.8mm, the plasticity and the toughness are good, the tensile strength reaches 348-; the intermediate annealing is only carried out once in the drawing process, so that the preparation efficiency of the magnesium alloy wire material is improved, and the production cost is reduced. The method is suitable for preparing the high-strength magnesium alloy wire.)

1. A high-strength magnesium alloy wire is characterized in that: the high-strength magnesium alloy wire consists of 1 to 1.08 percent of Al, 0.24 to 0.3 percent of Ca, 0.5 to 0.68 percent of Mn and the balance of Mg according to mass percentage.

2. The high strength magnesium alloy wire according to claim 1, wherein: the high-strength magnesium alloy wire consists of 1.08 percent of Al, 0.24 percent of Ca, 0.68 percent of Mn and the balance of Mg according to mass percentage.

3. A preparation method of a high-strength magnesium alloy wire is characterized by comprising the following steps: the preparation method of the high-strength magnesium alloy wire is carried out according to the following steps:

firstly, weighing pure magnesium, Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy as raw materials according to the mass ratio of each element of the high-strength magnesium alloy wire;

secondly, the crucible is placed in a heating furnace, and CO is introduced₂And SF₆Adjusting the furnace temperature to 760 ℃, adding pure magnesium into the crucible, preserving the temperature for 10min after the pure magnesium is completely melted, then reducing the furnace temperature to 740 ℃, sequentially adding Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy, and performing complete melting of one raw material and surface deslagging before adding new raw materials each time; after all the raw materials are melted, reducing the furnace temperature to 720 ℃, manually stirring for 5-8min,standing for 20min, and removing slag on the surface after standing; finally, immersing the crucible in water for cooling, and demolding to obtain an ingot;

thirdly, carrying out homogenizing annealing treatment on the ingot at 490-500 ℃ for 55-60 min, and carrying out water cooling; then extruding the cast ingot into a bar;

fourthly, carrying out solid solution on the extruded bar for 10-11 min at 490-500 ℃ in an argon atmosphere, and then carrying out water cooling;

fifthly, polishing the bar after solid solution, then continuously carrying out 19-pass hot drawing, and immediately cooling to room temperature after each hot drawing; annealing after the 19-pass hot drawing is finished; carrying out 5-pass hot drawing after annealing, and immediately cooling to room temperature after each hot drawing to finish the process;

in the hot drawing process, the area reduction rate of each pass is 10-20%, the drawing speed is 30mm/s, and the drawing temperature is 300-400 ℃.

4. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: in the first step, the mass fraction of Al in the Mg-Al alloy is 28-30 percent; the mass fraction of Ca in the Mg-Ca alloy is 13-15%; the mass fraction of Mn in the Mg-Mn alloy is 1.3-2.5%.

5. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: in the first step, the high-strength magnesium alloy wire consists of 1-1.08% of Al, 0.24-0.3% of Ca, 0.5-0.68% of Mn and the balance of Mg in percentage by mass.

6. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: second, SF in the mixed protective gas₆The volume percentage of (A) is 0.3-0.8%, and the rest is CO₂。

7. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: step three, the extrusion process comprises the following steps: the extrusion temperature is 330-350 ℃, the extrusion ratio is 20, the extrusion speed is 45-50 mm/s, and the extrusion outlet speed is 60 m/min.

8. The method for producing a high-strength magnesium alloy wire according to claim 7, wherein: step three, the extrusion process comprises the following steps: the extrusion temperature is 340 ℃, the extrusion ratio is 20, the extrusion speed is 45-50 mm/s, and the extrusion outlet speed is 60 m/min.

9. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: and step five, in the hot drawing process, the reduction rate of each pass is 15%, the drawing speed is 30mm/s, and the drawing temperature is 300-.

10. The method for producing a high-strength magnesium alloy wire according to claim 3, wherein: and fifthly, in the hot drawing process, the reduction rate of each pass is 15%, the drawing speed is 30mm/s, and the drawing temperature is 350 ℃.

Technical Field

The invention relates to a magnesium alloy wire and a preparation method thereof

Background

In recent years, rapid development of the automobile industry has made a great contribution to the world economy, but has brought about two serious social problems of environmental pollution and energy shortage. Therefore, the automobile industry needs to take a sustainable development path for energy conservation and emission reduction. The automobile reduces energy consumption and improves fuel economy through light weight of the automobile, and the automobile fuel is an important technology for promoting sustainable development of the automobile industry. The automobile wire harness accounts for 2% of the total mass of the automobile, and the space for arranging the automobile wire harness is smaller and smaller with the increase of the automobile electronic equipment, so the light weight of the automobile wire harness becomes more and more important.

The magnesium alloy is the lightest structural material applied to engineering at present, and the high-performance magnesium alloy wire has wide application prospect, such as being applied to automobile weight reduction, medical materials, welding wires and the like on automobile parts, and has great influence on the light weight of the automobile wire harness if the magnesium alloy is applied to the automobile wire harness. Currently, wires such as WE43 (magnesium alloy containing 4 wt.% of Y element and 3 wt.% of rare earth element), Mg-Gd-Y-Zn-Zr, and AZ31 (magnesium alloy containing 3 wt.% of Al element and 1 wt.% of Zn element) are the most studied, although the addition of rare earth element can improve the formability of magnesium alloy and improve the toughness of magnesium alloy, however, the commercial commercialization of rare earth magnesium alloy is hindered due to high cost. AZ31 was the most used aluminum alloy at present, but it did not reach the high strength required when making wire from it.

In the low-cost, high-strength and high-toughness wrought magnesium alloy without rare earth elements, the Mg-Al-Ca-Mn alloy becomes the wrought magnesium alloy with the best application prospect at present due to the advantages of high strength, good plasticity, good casting performance, good corrosion resistance and the like. However, since magnesium alloy itself is a hexagonal metal (HCP), the formability is limited, and drawing into a wire is difficult, and it is difficult to obtain a wire rod having both high strength and high formability.

Disclosure of Invention

The invention provides a high-strength magnesium alloy wire and a preparation method thereof, aiming at solving the problems that the existing magnesium alloy has poor formability and is difficult to draw into wires.

The high-strength magnesium alloy wire material consists of 1 to 1.08 percent of Al, 0.24 to 0.3 percent of Ca, 0.5 to 0.68 percent of Mn and the balance of Mg according to mass percentage.

Al: al is a main alloying element, and participates in solid solution strengthening and precipitation strengthening to improve the strength and corrosion resistance of the magnesium alloy. The tensile strength of the existing 'Mg-Al-Ca-Mn alloy' can reach 320MPa when the Al content reaches more than 2.7%, and in the invention, when the Al content is 1-1.08%, the tensile strength of the magnesium alloy is improved to 431MPa, and the ductility is good; after peak aging treatment, more Guinier-Preston (G.P) areas and nano Al are formed₂Ca phase, in Mg-Al-Ca-Mn alloy, region G.P and nano Al₂Ca has no influence on the relative elongation, and the elongation is slightly increased even after the aging treatment.

Ca: ca is an effective grain refiner, pinning grain boundaries due to the formation of Ca-containing intermetallic compounds at the grain boundaries. Meanwhile, Ca can improve the oxidation resistance and the flame resistance. Since the atomic radius of Ca is large, the addition of Ca can weaken the strength of the extrusion texture, indicating that Ca has similar behavior to rare earth elements when alloyed with Mg.

The content of Ca needs to be related to Al, and as the Ca/Al ratio increases, the second phase decreases, the recrystallized grain size decreases, the basal texture increases, and the like. The Ca/Al ratio of the selected material is smaller, and the addition of Ca element can form Al₂The Ca phase, Ca element segregates to the grain boundary, which is different from the Ca action effect in the existing 'Mg-Al-Ca-Mn alloy'. The Ca content of the invention is only 0.24-0.3%, the tensile strength can reach 348-431MPa, and the Ca content of the existing Mg-Al-Ca-Mn alloy can reach 320MPa when being more than 1.7%.

Mn: the Mn acts with Al to generate an Al-Mn phase pinning crystal boundary to inhibit the growth of crystal grains, meanwhile, the nano Al-Mn phase can improve the mechanical property of the Mg-Al-Ca series alloy, and the surface quality can be ensured when the Mn content is selected to be 0.5-0.68%.

The preparation method of the high-strength magnesium alloy wire is carried out according to the following steps:

firstly, weighing pure magnesium, Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy as raw materials according to the mass ratio of each element of the high-strength magnesium alloy wire;

secondly, the crucible is placed in a heating furnace, and CO is introduced₂And SF₆Adjusting the furnace temperature to 760 ℃, adding pure magnesium into the crucible, preserving the temperature for 10min after the pure magnesium is completely melted, then reducing the furnace temperature to 740 ℃, sequentially adding Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy, and performing complete melting of one raw material and surface deslagging before adding new raw materials each time; after all the raw materials are melted, reducing the furnace temperature to 720 ℃, manually stirring for 5-8min, standing for 20min, and then removing slag on the surface; finally, immersing the crucible in water for cooling, and demolding to obtain an ingot;

before smelting, polishing all raw materials to remove surface oxide skin; the inside of the crucible is ensured to be clean, and the influence of residual impurities on alloy components is avoided;

thirdly, carrying out homogenizing annealing treatment on the ingot at 490-500 ℃ for 55-60 min, and carrying out water cooling; then extruding the cast ingot into a bar;

fourthly, carrying out solid solution on the extruded bar for 10-11 min at 490-500 ℃ in an argon atmosphere, and then carrying out water cooling;

fifthly, polishing the bar after solid solution, then continuously carrying out 19-pass hot drawing, and immediately cooling to room temperature after each hot drawing; annealing after the 19-pass hot drawing is finished; carrying out 5-pass hot drawing after annealing, and immediately cooling to room temperature after each hot drawing to finish the process;

in the hot drawing process, the area reduction rate of each pass is 10-20%, the drawing speed is 30mm/s, and the drawing temperature is 300-400 ℃. The hot drawing process can prevent the wire from being broken; before hot drawing, the bar needs to be polished, and before drawing in each pass, the wire and the wire drawing die are lubricated by using a lubricant.

The principle and the beneficial effects of the invention are as follows:

1. the invention can obtain the wire with the diameter of 1.6-3.8mm, the tensile strength of the wire reaches 348-; the grain size of the wire is in submicron level; the intermediate annealing is only carried out once in the drawing process, so that the preparation efficiency of the magnesium alloy wire material is improved, and the production cost is reduced.

2. The magnesium alloy is in a HCP structure, the number of slip systems of the magnesium alloy is small under room temperature deformation, and a non-basal plane slip system is difficult to start, so that the magnesium alloy is difficult to deform at room temperature. The invention can improve the formability through hot working and alloy component regulation. The microstructure of the wire after hot processing is a double-peak microstructure, the tensile strength can be improved by forming a non-recrystallization area, and the deformation texture can be weakened by forming a recrystallization area, so that the plasticity of the material can be improved. The bimodal structure suppresses local strain in the unrecrystallized region by regulating strain distribution, thereby improving plastic deformation. In addition, non-basal plane slippage is activated due to thermal deformation, and the start of multi-linear slippage can coordinate the strain of the polycrystalline metal structural material, so that the plastic deformation capacity of the magnesium alloy is improved.

3. The alloy can realize Al and Ca co-segregation induced grain boundary pinning after 5-pass hot drawing, and the Al and Ca co-segregation induced grain boundary pinning can be reserved without annealing after the hot drawing, so that a dynamic recrystallization mechanism is influenced to weaken the deformation texture of the magnesium alloy. The large amount of crystal boundary and high-density dislocation promote solute elements to diffuse in the crystal boundary and dislocation boundary, so that large grains are changed into small grains, and submicron grains are formed. In addition to improving strength, refining grains typically at submicron levels can also result in good plasticity and toughness.

4. The high-strength magnesium alloy wire material obtained by the invention has the cost lower than WE43 and magnesium alloy containing rare earth elements such as Mg-Gd-Y-Zn-Zr and the like, and the strength reaches 431MPa and is better than AZ 31.

Drawings

FIG. 1 shows the results obtained in example 1Microstructure picture of the wire material;

FIG. 2 shows the results obtained in example 1Microstructure picture of the wire material;

FIG. 3 shows the results obtained in example 1A mechanical property diagram of the wire material;

FIG. 4 shows the results obtained in example 1ECCI pictures of wires;

FIG. 5 shows the results obtained in example 1TEM pictures of the wires.

Detailed Description

The technical scheme of the invention is not limited to the specific embodiments listed below, and any reasonable combination of the specific embodiments is included.

The first embodiment is as follows: the high-strength magnesium alloy wire material of the embodiment comprises, by mass, 1-1.08% of Al, 0.24-0.3% of Ca, 0.5-0.68% of Mn and the balance of Mg.

The embodiment has the following beneficial effects:

the method can obtain the wire with the diameter of 1.6-3.8mm, the tensile strength of the wire reaches 348-.

The high-strength magnesium alloy wire obtained by the embodiment has the advantages that the cost is lower than that of WE43 and magnesium alloy containing rare earth elements such as Mg-Gd-Y-Zn-Zr, the strength reaches 431MPa and is better than that of AZ 31.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the high-strength magnesium alloy wire consists of 1.08 percent of Al, 0.24 percent of Ca, 0.68 percent of Mn and the balance of Mg according to mass percentage.

The third concrete implementation mode: the preparation method of the high-strength magnesium alloy wire material of the embodiment is carried out according to the following steps:

firstly, weighing pure magnesium, Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy as raw materials according to the mass ratio of each element of the high-strength magnesium alloy wire;

secondly, the crucible is placed in a heating furnace, and CO is introduced₂And SF₆Adjusting the furnace temperature to 760 ℃, adding pure magnesium into the crucible, preserving the temperature for 10min after the pure magnesium is completely melted, then reducing the furnace temperature to 740 ℃, sequentially adding Mg-Al alloy, Mg-Ca alloy and Mg-Mn alloy, and performing complete melting of one raw material and surface deslagging before adding new raw materials each time; after all the raw materials are melted, reducing the furnace temperature to 720 ℃, manually stirring for 5-8min, standing for 20min, and then removing slag on the surface; finally, immersing the crucible in water for cooling, and demolding to obtain an ingot;

before smelting, polishing all raw materials to remove surface oxide skin; the inside of the crucible is ensured to be clean, and the influence of residual impurities on alloy components is avoided;

thirdly, carrying out homogenizing annealing treatment on the ingot at 490-500 ℃ for 55-60 min, and carrying out water cooling; then extruding the cast ingot into a bar;

fourthly, carrying out solid solution on the extruded bar for 10-11 min at 490-500 ℃ in an argon atmosphere, and then carrying out water cooling;

fifthly, polishing the bar after solid solution, then continuously carrying out 19-pass hot drawing, and immediately cooling to room temperature after each hot drawing; annealing after the 19-pass hot drawing is finished; carrying out 5-pass hot drawing after annealing, and immediately cooling to room temperature after each hot drawing to finish the process;

in the hot drawing process, the area reduction rate of each pass is 10-20%, the drawing speed is 30mm/s, and the drawing temperature is 300-400 ℃. The hot drawing process can prevent the wire from being broken; before hot drawing, the bar needs to be polished, and before drawing in each pass, the wire and the wire drawing die are lubricated by using a lubricant.

1. The method can obtain the wire with the diameter of 1.6-3.8mm, the tensile strength of the wire reaches 348-; the grain size of the wire is in submicron level; the intermediate annealing is only carried out once in the drawing process, so that the preparation efficiency of the magnesium alloy wire material is improved, and the production cost is reduced.

2. The magnesium alloy is in a HCP structure, the number of slip systems of the magnesium alloy is small under room temperature deformation, and a non-basal plane slip system is difficult to start, so that the magnesium alloy is difficult to deform at room temperature. The present embodiment can improve formability by hot working and alloy composition control. The microstructure of the wire after hot processing is a double-peak microstructure, the tensile strength can be improved by forming a non-recrystallization area, and the deformation texture can be weakened by forming a recrystallization area, so that the plasticity of the material can be improved. The bimodal structure suppresses local strain in the unrecrystallized region by regulating strain distribution, thereby improving plastic deformation. In addition, non-basal plane slippage is activated due to thermal deformation, and the start of multi-linear slippage can coordinate the strain of the polycrystalline metal structural material, so that the plastic deformation capacity of the magnesium alloy is improved.

3. The alloy of the embodiment can realize Al and Ca co-segregation induced grain boundary pinning after 5 times of hot drawing, and the Al and Ca co-segregation induced grain boundary pinning can be reserved without annealing after the hot drawing, so that a dynamic recrystallization mechanism is influenced to weaken the deformation texture of the magnesium alloy. The large amount of crystal boundary and high-density dislocation promote solute elements to diffuse in the crystal boundary and dislocation boundary, so that large grains are changed into small grains, and submicron grains are formed. In addition to improving strength, refining grains typically at submicron levels can also result in good plasticity and toughness.

4. The high-strength magnesium alloy wire obtained by the embodiment has the advantages that the cost is lower than that of WE43 and magnesium alloy containing rare earth elements such as Mg-Gd-Y-Zn-Zr, the strength reaches 431MPa and is better than that of AZ 31.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: in the first step, the mass fraction of Al in the Mg-Al alloy is 28-30 percent; the mass fraction of Ca in the Mg-Ca alloy is 13-15%; the mass fraction of Mn in the Mg-Mn alloy is 1.3-2.5%.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: in the first step, the high-strength magnesium alloy wire consists of 1-1.08% of Al, 0.24-0.3% of Ca, 0.5-0.68% of Mn and the balance of Mg in percentage by mass.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: second, SF in the mixed protective gas₆The volume percentage of (A) is 0.3-0.8%, and the rest is CO₂。

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: step three, the extrusion process comprises the following steps: the extrusion temperature is 330-350 ℃, the extrusion ratio is 20, the extrusion speed is 45-50 mm/s, and the extrusion outlet speed is 60 m/min.

The specific implementation mode is eight: the seventh embodiment is different from the seventh embodiment in that: step three, the extrusion process comprises the following steps: the extrusion temperature is 340 ℃, the extrusion ratio is 20, the extrusion speed is 45-50 mm/s, and the extrusion outlet speed is 60 m/min.

The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: and step five, in the hot drawing process, the reduction rate of each pass is 15%, the drawing speed is 30mm/s, and the drawing temperature is 300-.

The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: and fifthly, in the hot drawing process, the reduction rate of each pass is 15%, the drawing speed is 30mm/s, and the drawing temperature is 350 ℃.

Example 1:

in the embodiment, the Mg-1.08Al-0.24Ca-0.68Mn (wt.%) magnesium alloy is used for quickly preparing the high-strength magnesium alloy wire material through hot drawing, and the method is specifically completed according to the following steps:

turning the cast alloy ingot into a round bar ingot with the diameter of 43mm, carrying out hot extrusion on the round bar ingot into a bar with the diameter of 9.6mm, and then carrying out solid solution at 500 ℃ for 10 min;

step two, polishing the end part of the bar obtained in the step one until the end part can pass through a wire drawing die, lubricating the bar and the wire drawing die by using a lubricant, heating the wire drawing die to 400 ℃, then installing the bar on the wire drawing die, carrying out 19-pass hot drawing on the bar, immediately carrying out water cooling on the wire material after being discharged to room temperature, wherein the drawing speed is 30mm/s, and the drawing temperature is 370 ℃;

continuously carrying out hot drawing on each pass of wire diameter change: 9.00mm → 8.50mm → 8.00mm → 7.50mm → 7.00mm → 6.50mm → 6.00mm → 5.50mm → 5.00mm → 4.50mm → 4.00mm → 3.80mm → 3.50mm → 3.20mm → 3.00mm → 2.80mm → 2.60mm → 2.40mm → 2.20 mm;

step three, carrying out hot drawing on the step twoAnnealing the wire material at 400 deg.C for 10min, air cooling to room temperature, annealingThe average grain size of the wire was 4 μm (see FIG. 1);

step four, carrying out hot drawing on the wire for 5 times, wherein the hot drawing temperature is 300 ℃, the drawing speed is 30mm/s, the wire after being demoulded is immediately cooled to room temperature, and the diameter of the wire in each hot drawing time is changed: 2.00mm → 1.90mm → 1.80mm → 1.70mm → 1.60 mm; FIG. 2 can be seenThe average grain size of the wire is 0.47 mu m;the mechanical property chart of the wire is shown in FIG. 3, and it can be known from FIG. 3,the strength of the wire is as high as 431 MPa. FIG. 4 shows the results obtained in example 1ECCI pictures of wires; FIG. 4 can be seen that the combination of the simultaneous unrecrystallized and recrystallized regions constitutes a bimodal microstructure; FIG. 5 shows the results obtained in example 1TEM pictures of the wires. Fig. 5 shows that Al and Mn segregate in the grain boundaries.