阅读说明：本技术 电流辅助作用下高强塑性镁合金薄板的制备装置及方法 (Device and method for preparing high-strength plastic magnesium alloy sheet under current assistance ) 是由 聂慧慧 梁伟 刘群峰 李线绒 郑留伟 于 2021-07-13 设计创作，主要内容包括：本发明目的在于提供一种可以获得强度高、塑性好的镁合金薄板的电流辅助作用下高强塑性镁合金薄板的制备装置及方法,属于有色金属材料塑性变形及应用的技术领域,本发明在脉冲电流辅助作用下对轧制或挤压的镁合金薄板进行余弦微弯,随后将变形后的镁合金薄板放置在限制宽度的模具中进行压平,迫使镁合金薄板发生整体压缩变形以激发拉伸孪生变形系统启动,充分发挥脉冲电流的电致塑性效应以及促进拉伸孪晶形核的作用,进一步提高拉伸孪晶体积分数,在拉伸孪晶切割晶粒与脉冲电流共同诱导再结晶的作用下,得到主要由再结晶和拉伸孪晶组成的混合组织,最终获得强度高、塑性好的镁合金薄板。(The invention aims to provide a device and a method for preparing a high-strength plastic magnesium alloy sheet under the current auxiliary action of the magnesium alloy sheet with high strength and good plasticity, belonging to the technical field of plastic deformation and application of non-ferrous metal materials Magnesium alloy sheet with good plasticity.)

1. A preparation facilities of high strength plasticity magnesium alloy sheet under current auxiliary action which characterized in that: comprises a furnace box, a control system, an open-close type bending die, an open-close type constraint straightening die and a pulse power supply for producing high-frequency current;

an upper pressure head and a lower pressure head are symmetrically arranged at the upper end and the lower end of the furnace box, the upper pressure head and the lower pressure head are fixed through a top seat and a base which are positioned at the outer side of the furnace box respectively, a graphite backing plate is arranged at the bottom of the upper pressure head, the other ends, opposite to the upper pressure head and the lower pressure head, of the upper pressure head are connected with an upper electrode and a lower electrode respectively, one ends of the upper electrode and the lower electrode are connected with the positive electrode and the negative electrode of a pulse power supply respectively through wires, an open-close type bending die or an open-close type constraint straightening die are positioned between the graphite backing plate and the lower pressure head, thermocouple jacks are respectively arranged on the open-close type bending die and the open-close type constraint straightening die, and thermocouples are arranged in the thermocouple jacks; the control system is respectively connected with the pulse power supply, the upper electrode, the lower electrode, the thermocouple and the furnace box through leads.

2. The device for preparing the high-strength plastic magnesium alloy sheet under the current assistance according to claim 1, is characterized in that: the open-close type bending die comprises an upper die I and a lower die I, wherein a wavy cavity is formed between the upper die I and the lower die I.

3. The device for preparing the high-strength plastic magnesium alloy sheet under the current assistance according to claim 2, is characterized in that: the open-close type constraint straightening die comprises an upper die II and a lower die II, a rectangular cavity is arranged between the upper die II and the lower die II, and baffles are arranged at two ends of the lower die II respectively.

4. The device for preparing the high-strength plastic magnesium alloy sheet under the current assistance according to claim 3, is characterized in that: and the thermocouple jacks are respectively positioned on the lower die I and the lower die II.

5. A preparation method of a high-strength plastic magnesium alloy sheet under the current assistance action is characterized by comprising the following steps: the method comprises the following steps:

firstly, selecting a magnesium alloy sheet according to a die, and placing the magnesium alloy sheet in an open-close type bending die for assembly;

secondly, placing the assembled parts between an upper electrode and a lower electrode under the action of high-frequency pulses, electrifying, heating a furnace box and simultaneously applying a load to carry out bending deformation on the magnesium alloy sheet;

and thirdly, placing the bent and deformed magnesium alloy sheet in an open-close type constraint straightening die for assembly, placing the assembled part between an upper electrode and a lower electrode under the action of high-frequency pulses for electrifying, heating a furnace box and applying a load at the same time, and constraining and straightening the magnesium alloy sheet.

6. The method for preparing the high-strength plastic magnesium alloy sheet under the current assistance according to claim 5, is characterized in that: in the second step, the temperature of the furnace box is 200 ℃, the pressure in the furnace box is lower than the atmospheric pressure, the applied load pressure is 1-3MPa, and the pressure applying time is 5-20 min.

7. The method for preparing the high-strength plastic magnesium alloy sheet under the current assistance according to claim 5, is characterized in that: in the third step, the temperature of the furnace box is 200 ℃, the pressure in the furnace box is lower than the atmospheric pressure, the applied load pressure is 1-3MPa, and the pressure applying time is 5-20 min.

Technical Field

The invention belongs to the technical field of plastic deformation and application of non-ferrous metal materials, and particularly relates to a device and a method for preparing a high-strength plastic magnesium alloy sheet under the current assistance effect.

Background

The magnesium alloy is the lightest metal structure material in the current practical application, has the advantages of small density, high specific strength and specific stiffness, good heat transfer property and the like, and has wide application prospect in the fields of automobiles, aerospace navigation instruments, 3C product shells and the like. However, magnesium alloy stamping blank sheets are mostly prepared by rolling or extrusion methods, so that the texture of the basal plane is obvious, and the anisotropy of the structure and the performance is obvious, which causes that the strength of the magnesium alloy sheet is not high and the plastic forming performance is poor.

The conventional strong plastic deformation modes such as equal channel extrusion, cumulative rolling, high-pressure torsion and the like can only improve the strength. The external electric field can improve the plastic deformation capacity of the metal material and reduce the residual stress, and is currently applied to the plastic deformation process to omit the subsequent heat treatment process. Therefore, the method for simultaneously improving the strength and the plastic forming performance of the magnesium alloy sheet is an effective method for simultaneously improving the strength and the plastic forming performance of the magnesium alloy sheet while refining the crystal grains.

Disclosure of Invention

The invention aims to provide a device and a method for preparing a high-strength plastic magnesium alloy sheet under the current assistance effect, and finally the magnesium alloy sheet with high strength and good plasticity is obtained.

The invention adopts the following technical scheme:

a device for preparing a high-strength plastic magnesium alloy sheet under the current assistance effect comprises a furnace box, a control system, an open-close type bending die, an open-close type constraint straightening die and a pulse power supply for producing high-frequency current;

an upper pressure head and a lower pressure head are symmetrically arranged at the upper end and the lower end of the furnace box, the upper pressure head and the lower pressure head are fixed through a top seat and a base which are positioned at the outer side of the furnace box respectively, a graphite backing plate is arranged at the bottom of the upper pressure head, the other ends, opposite to the upper pressure head and the lower pressure head, of the upper pressure head are connected with an upper electrode and a lower electrode respectively, one ends of the upper electrode and the lower electrode are connected with the positive electrode and the negative electrode of a pulse power supply respectively through wires, an open-close type bending die or an open-close type constraint straightening die are positioned between the graphite backing plate and the lower pressure head, thermocouple jacks are respectively arranged on the open-close type bending die and the open-close type constraint straightening die, and thermocouples are arranged in the thermocouple jacks; the control system is respectively connected with the pulse power supply, the upper electrode, the lower electrode, the thermocouple and the furnace box through leads.

The open-close type bending die comprises an upper die I and a lower die I, wherein a wavy cavity is formed between the upper die I and the lower die I.

The open-close type constraint straightening die comprises an upper die II and a lower die II, a rectangular cavity is arranged between the upper die II and the lower die II, and baffles are arranged at two ends of the lower die II respectively.

And the thermocouple jacks are respectively positioned on the lower die I and the lower die II.

A preparation method of a high-strength plastic magnesium alloy sheet under the current assistance effect comprises the following steps:

firstly, selecting a magnesium alloy sheet according to a die, and placing the magnesium alloy sheet in an open-close type bending die for assembly;

secondly, placing the assembled parts between an upper electrode and a lower electrode under the action of high-frequency pulses, electrifying, heating a furnace box and simultaneously applying a load to carry out bending deformation on the magnesium alloy sheet;

and thirdly, placing the bent and deformed magnesium alloy sheet in an open-close type constraint straightening die for assembly, placing the assembled part between an upper electrode and a lower electrode under the action of high-frequency pulses for electrifying, heating a furnace box and applying a load at the same time, and constraining and straightening the magnesium alloy sheet.

Further, in the second step, the temperature of the furnace box is 200 ℃, the pressure in the furnace box is lower than the atmospheric pressure, the applied load pressure is 1-3MPa, and the pressure applying time is 5-20 min.

Further, in the third step, the temperature of the furnace box is 200 ℃, the pressure in the furnace box is lower than the atmospheric pressure, the applied load pressure is 1-3MPa, and the pressure applying time is 5-20 min.

The invention has the following beneficial effects:

the invention aims at the problems of lower strength and poor plastic forming performance of the magnesium alloy sheet at room temperature, provides a method for preparing the magnesium alloy sheet with high strength and plasticity by forcing the magnesium alloy sheet to generate integral compression deformation in a die under the auxiliary action of pulse current, fully exerting the functions of stretching twin crystal cutting crystal grains and inducing recrystallization together with the pulse current, obtaining a mixed structure mainly comprising recrystallization and stretching twin crystal, and finally synchronously improving the strength and the plasticity of the magnesium alloy sheet.

Drawings

FIG. 1 is a diagram of a deformation preparation state of a method for manufacturing a high-strength plastic magnesium alloy sheet under the assistance of current provided by an embodiment of the invention;

FIG. 2 is a deformation state diagram of a method for manufacturing a high-strength plastic magnesium alloy sheet under the assistance of current provided by an embodiment of the invention;

FIG. 3 is a diagram of a straightening preparation state of a method for manufacturing a high-strength plastic magnesium alloy sheet under the assistance of current provided by an embodiment of the invention;

fig. 4 is a straightening state diagram of a method for preparing a high-strength plastic magnesium alloy sheet under the current assistance effect provided by the embodiment of the invention.

Fig. 5 is a comparison graph of an original structure and a deformed structure of a magnesium alloy sheet under the current assistance provided by an example of the invention, wherein (a) is the original structure graph, and (b) is the deformed structure graph.

Fig. 6 is a mechanical property curve chart of the magnesium alloy sheet before and after deformation under the current assistance provided by the embodiment of the invention.

Wherein: 1-an upper electrode; 2-a top seat; 3-a furnace box; 4, an upper pressure head; 5-a graphite backing plate; 6-upper die II; 7-lower die II; 8-thermocouple jack; 9-pressing head; 10-a thermocouple; 11-a base; 12-a lower electrode; 13-a pulsed power supply; 14-a display; 15-a control box; 16-power switch button; 17-press control button; 18-temperature control button; 19-current adjustment button; 20-voltage adjustment button; 21-frequency adjustment button; 22-upper mould I; 23-lower die I; 24-magnesium alloy sheet with bending deformation; 25-straightened magnesium alloy sheet.

Detailed Description

The invention is further explained with reference to the accompanying drawings.

As shown in the figure, the preparation method of the high-strength plastic magnesium alloy sheet under the current assistance effect comprises the following steps:

(1) selecting a magnesium alloy sheet with a proper size according to a die, and placing the magnesium alloy sheet in a bending die for assembly;

(2) placing the assembled parts between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulses, electrifying, heating and applying load simultaneously, and performing bending deformation on the magnesium alloy sheet;

(3) and similarly, placing the magnesium alloy sheet in a straightening die for assembly, placing the assembled part between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulses, electrifying, heating and applying load simultaneously, and constraining and straightening the magnesium alloy sheet.

The size of the magnesium alloy plate in the step (1) is 32mm multiplied by 26mm multiplied by 1mm, the manufacturing material of the open-close type press bending die is conductive graphite, a cavity is wave-shaped, and the wave curve equation is Y = -2cos (pi/20) x;

placing the assembled part between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulse, electrifying, heating and simultaneously applying load, and performing bending deformation on the magnesium alloy sheet, wherein the temperature in the furnace is 200 ℃, the pressure in the furnace is lower than the atmospheric pressure, the pressure is 1-3MPa, and the pressure application time is 5-20 min;

and (3) placing the magnesium alloy sheet in a straightening die for assembly, placing the assembled part between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulses, electrifying, heating and simultaneously applying load, constraining the magnesium alloy sheet in the straightening furnace to have the temperature of 200 ℃, the pressure in the furnace lower than the atmospheric pressure, the pressure of 1-3MPa, and the pressure applying time of 5-20 min.

A device for preparing a high-strength plastic magnesium alloy sheet under the current assistance effect comprises a furnace box 3, a control system 15, an open-close type bending die, an open-close type constraint straightening die and a pulse power supply 13 for generating high-frequency current.

The stove case 3 is including relative last pressure head 4 and lower pressure head 9 that sets up, it has graphite backing plate 5 to go up pressure head 4 and lower pressure head 9 centre, it is connecting respectively to go up pressure head 4 and lower pressure head 9, it is fixed by footstock 2 and base 11 respectively to go up pressure head 4 and lower pressure head 9, it links to each other with pulse power supply 13 through the wire to go up electrode 1 and lower electrode 12, it links to each other with control system through wire and lower electrode 12 to go up electrode 1, stove case 3 links to each other with control system through the wire.

The control system is provided with a display 14 for displaying the current, the temperature and the loading pressure of the furnace box 3, a power switch button 16, a press machine control button 17, a temperature control button 18, a current adjusting button 19, a voltage adjusting button 20 and a frequency adjusting button 21.

A die placing space is formed between the upper pressing head 4 and the lower pressing head 9; the open-close type bending die comprises an upper die I22 and a lower die I23, a die cavity is wavy, and the curve equation of the die cavity is Y = -2cos (pi/20) x; the open-close type constraint straightening die comprises an upper die II 6 and a lower die II 7, and a die cavity is rectangular.

Furthermore, the open-close type bending die is made of graphite materials; the open-close type restraint straightening die is made of graphite materials.

Examples

In this example, the annealed AZ31 magnesium alloy sheet was subjected to the electric current machining according to the method and apparatus described above using the annealed AZ31 magnesium alloy sheet as an experimental subject. The size of the open-close type bending die is 32mm multiplied by 26mm multiplied by 20 mm, and the surface roughness Ra of the die cavity is 0.08-0.16 mu m; the size of the open-close type constraint straightening die is 60mm multiplied by 50mm multiplied by 34mm, and the surface roughness Ra of the die cavity is 0.08-0.16 mu m; the length of the magnesium alloy plate in the Rolling Direction (RD) is 26mm, the length of the magnesium alloy plate in the Transverse Direction (TD) is 32mm, and the thickness of the magnesium alloy plate is 1 mm; the method comprises the following specific steps:

(1) magnesium alloy sheets were cut to a size of 32mm by 26mm by 1 mm.

(2) And (5) polishing, namely polishing and flattening all the surfaces of the magnesium alloy plate.

(3) And assembling the magnesium alloy thin plate in a bending die.

(4) And placing the assembled parts between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulses, electrifying, heating and applying load to carry out bending deformation on the magnesium alloy sheet.

Opening a furnace chamber, placing a die and a graphite pad between an upper pressure head and a lower pressure head, sequentially arranging a bending die and a graphite backing plate on the lower pressure head, adjusting the positions of the graphite backing plate and the upper pressure head to press the graphite backing plate and fix the whole, and closing the furnace chamber.

Secondly, the temperature detection is realized by connecting a thermocouple in the furnace with a temperature control system, and the real-time temperature is displayed in a display, so that the temperature in the furnace can be monitored in real time.

And thirdly, turning on a power switch button of the control system, adjusting a temperature adjusting button of the control system, and raising the temperature in the furnace from room temperature to 200 ℃ for 5 min.

Turning on the high-frequency current power supply, and regulating the current control button and the voltage control button to control the current and the voltage.

And sixthly, starting a pressure motor control system, and applying pressure to the bending die through an upper electrode and an upper pressure head, wherein the pressure intensity is 2 MPa, and the pressure time is 5 min.

And seventhly, closing the high-frequency current power supply, closing the pressure motor control system, cooling to room temperature along with the furnace, opening the furnace box, taking out the mold, and taking out the pressed and bent magnesium alloy plate from the mold.

(5) The method comprises the steps of polishing and flattening all surfaces of the bent magnesium alloy sheet, wherein the dimensions are 28mm multiplied by 26mm multiplied by 1mm, placing the magnesium alloy sheet in constraint for assembly, placing the assembled parts between an upper pressure head electrode and a lower pressure head electrode under the action of high-frequency pulse for electrifying, heating and applying load simultaneously, and constraining and straightening the magnesium alloy sheet.

Opening a furnace chamber, placing a mold and a graphite backing plate between an upper pressure head and a lower pressure head, wherein the lower pressure head is sequentially provided with a straightening mold and the graphite backing plate, adjusting the positions of the graphite backing plate and the upper pressure head to press the graphite backing plate and fix the whole, and closing the furnace chamber.

Secondly, the temperature detection is realized by connecting a thermocouple in the furnace with a temperature control system, and the real-time temperature is displayed in a display, so that the temperature in the furnace can be monitored in real time.

And thirdly, turning on a power switch button of the control system, adjusting a temperature adjusting button of the control system, and raising the temperature in the furnace from room temperature to 200 ℃ for 5 min.

Turning on the high-frequency current power supply, and regulating the current control button and the voltage control button to control the current and the voltage.

And sixthly, starting a pressure motor control system, and applying pressure to the straightening die through an upper electrode and an upper pressure head, wherein the pressure intensity is 2 MPa, and the pressure time is 5 min.

And seventhly, closing the high-frequency current power supply, closing the pressure motor control system, cooling along with the furnace to room temperature, opening the furnace box, taking out the mold, and taking out the pressed magnesium alloy plate from the mold.

As can be seen from fig. 5 and 6: the original magnesium alloy sheet material has extremely uneven grain size, mainly consists of large grains and a small amount of fine grains and twin crystals. A large amount of stretching twin crystals appear after deformation, the initial large crystal grains in the magnesium alloy are cut by the twin crystals, and the crystal grain refining effect is obvious. Thus, the strength and plasticity of the deformed sheet material are significantly improved compared to the original sheet material.