A method for composite processing of a magnesium alloy sheet

Abstract

The application discloses a kind of magnesium alloy plate composite processing method, mainly including the following steps: A, smelting and semi-continuous casting out the magnesium alloy bar of diameter Φ130mm-160mm;B, to ingot is carried out homogenization annealing treatment, process is: 350-420 ℃ after 16-50h heat preservation, take out air cooling;C, the ingot billet after homogenization annealing, blanking;Before extrusion, the billet and die are kept at 250-350 ℃ for 1-3h;After heat preservation, carry out width expansion extrusion, and extrusion ratio is 8-16, and the plate material with cross section width of 160-200mm and thickness of 7-14mm is extruded from die mouth;When extruding, the advancing speed of hydraulic rod is 0.5-3.5mm / s;Plate material is air-cooled after extrusion;D, after preheating at 280-320 ℃ for 20-30 minutes, carry out single direction rolling deformation with pass deformation amount of 20-30%, until thickness is reduced to 3.4-5.8mm;E, after rolling, carry out annealing at 280-320 ℃ for 10-20 minutes.The mechanical property of Mg alloy component prepared by the application is weak in anisotropy, and the forming problem of magnesium alloy plate anisotropy can be well solved, and the comprehensive mechanical property is excellent.

Description

TECHNICAL FIELD

[0001] The application relates to a magnesium alloy plate processing method, in particular to a composite processing method for reducing the anisotropy of the plate. BACKGROUND

[0002] Magnesium alloy is widely used in the fields of aerospace and automobile manufacturing due to its high specific strength, high specific stiffness, good corrosion resistance and excellent thermal conductivity. Rolling is the most conventional plastic processing method for producing magnesium alloy plates, but due to the crystal structure characteristics of magnesium alloy, specific texture is easily formed in the rolling process, which seriously affects the mechanical properties of the rolled plate and restricts the application range of the magnesium alloy plate.

[0003] At present, although methods such as asynchronous rolling and cross rolling have been proposed to reduce the anisotropy of the magnesium alloy plate, these methods are not only complex and costly, but also cannot well solve the problem. It is urgent to invent an efficient and convenient processing method to reduce the anisotropy of the magnesium alloy plate, produce high-toughness quasi-isotropic magnesium alloy plates, broaden the application range of the magnesium alloy and exert the advantages of the magnesium resources in China. SUMMARY

[0004] The application provides a composite processing method for reducing the anisotropy of a magnesium alloy plate.

[0005] A composite processing method for a magnesium alloy plate, characterized in that the magnesium alloy has a mass percentage composition of Al: 3.0-9.0%, Zn: 1.0-2.5%, Mn: 0.1-0.8%, and the rest is Mg and non-removable impurities, and the processing method comprises the following steps.

[0006] A, melting and semi-continuous casting a magnesium alloy rod with a diameter of 130-160 mm;

[0007] B, performing homogenization annealing treatment on the cast ingot;

[0008] C, transporting and cutting the ingot after the homogenization annealing, to obtain a rod with a diameter of 120-150 mm; before extrusion, the rod and the die are kept at 250-350 DEG C for 1-3 h; after the keeping, the rod is loaded into an extrusion cylinder for width expansion extrusion, and the extrusion ratio is 8-16; the plate with a cross-sectional width of 160-200 mm and a thickness of 7-14 mm is extruded from the die mouth;

[0009] D, performing single-direction rolling deformation with a deformation amount of 20-30%, the rolling passes are more than two, the rolling direction is parallel to the extrusion direction, and the thickness is reduced to 3.4-5.8 mm;

[0010] E. annealing at 280-320℃ for 10-20 minutes after rolling.

[0011] Preferably, in step B, the homogenization annealing process is: holding at 350-420℃ for 16-50h, and then taking out the blank for air cooling.

[0012] Preferably, in step C, the pushing speed of the hydraulic rod during extrusion is 0.5-3.5mm / s; and the plate is air cooled after extrusion.

[0013] Preferably, in step D, before rolling, the plate is preheated at 280-320℃ for 20-30 minutes.

[0014] After step E, the plate has a room temperature yield strength≥220MPa, a tensile strength≥320MPa, an elongation≥12.0%, and the absolute value of the strength deviation in different directions is less than 15MPa, and the absolute value of the elongation deviation is less than 2%.

[0015] In the above scheme, the purpose of homogenizing the semi-continuous ingot is to dissolve the eutectic phase as much as possible, remove the casting residual stress, and thus improve the plastic forming ability of the ingot blank. The ingot blank after homogenization annealing is subjected to horizontal forward width extrusion, so as to promote the flow of metal along the width direction of the plate during deformation. The specific texture (grain preferred orientation) formed promotes the strength of the extruded plate in the width direction to be superior to that in the extrusion direction, and fine-grained structure is obtained to improve the comprehensive mechanical properties and secondary forming ability of the alloy. Subsequently, the strength in the rolling direction (i.e. the original extrusion direction) is improved during rolling, and the superposition of extrusion and rolling finally realizes the weakening of the anisotropy of the plate. Through the scientific integration of extrusion, rolling and annealing processes, a high-strength and high-toughness quasi-isotropic magnesium alloy plate is prepared.

[0016] Compared with the prior art, the present application has the following advantages: simple process, low cost. It can well solve the forming problem of the anisotropy of the magnesium alloy plate and has excellent comprehensive mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the optical microstructure photo of the rolled plate of Example 1;

[0018] Figure 2 is the pole figure and grain orientation diagram of the rolled plate of Example 1;

[0019] Figure 3 is the optical microstructure photo of the rolled plate of Example 2;

[0020] Figure 4 is the pole figure and grain orientation diagram of the rolled plate of Example 2;

[0021] Figure 5is the pole figure and schematic diagram of grain orientation of the rolling plate of Comparative Example 1;

[0022] Figure 6 is the pole figure and schematic diagram of grain orientation of the rolling plate of Comparative Example 2;

[0023] Figure 7 is the pole figure and schematic diagram of grain orientation of the rolling plate of Comparative Example 3. DETAILED DESCRIPTION

[0024] The present application is made by adjusting the processing parameters, and a large number of comparative experiments are made. The following examples are used to further illustrate the present application. These examples are used to illustrate the present application, but are not a limitation of the present application. Improvements to the present application process under the concept of the present application are within the scope of the present application.

[0025] Example 1

[0026] An alloy rod with a diameter of Φ160 mm is smelted and semi-continuously cast, and the mass percentage content of the alloy is Mg-4.8Al-2.4Zn-0.5Mn. The ingot is subjected to homogenization annealing treatment, and the process is 380℃ for 40h, and then air cooling. The ingot billet after homogenization annealing is transported and cut, and a rod with a diameter of Φ150 mm is obtained. The rod and the mold are kept at 280℃ for 2h. After the end of the heat preservation, the rod is loaded into the extrusion cylinder for width expansion extrusion, and the extrusion ratio is 12.1. A plate with a cross-sectional width of 175 mm and a thickness of 9.5 mm is extruded from the mold opening, and the pushing speed of the hydraulic rod during extrusion is 2mm / s. After the plate is extruded, it is air cooled. After preheating at 300℃ for 25 minutes, one-way rolling deformation with a deformation amount of 22% is carried out, a total of 2 passes, and the rolling direction is parallel to the extrusion direction, until the thickness is reduced to 5.8mm. After rolling, annealing is carried out at 320℃ for 12 minutes. The room temperature tensile mechanical properties of the obtained plate along the length (ED) and width (TD) directions are listed in Table 1, and the optical microstructure photos of the obtained plate are shown in FIG. 1, and the pole figure and schematic diagram of grain orientation of the rolling plate are shown in FIG. 2. Figure 1 Figure 2

[0027] Example 2

[0028] ​​An alloy bar with a diameter of Φ130 mm was smelted and semi-continuously cast, and the mass percentage content of the alloy was Mg-9.0Al-2.5Zn-0.8Mn. The ingot was subjected to homogenization annealing treatment, the process was 420 ℃ for 16 h, and then air cooling was performed. The ingot billet after homogenization annealing was cut and blanked to obtain a bar with a diameter of Φ120 mm. The bar and the die were kept at 350 ℃ for 1 h. After the end of the heat preservation, the bar was loaded into the extrusion cylinder for width expansion extrusion, and the extrusion ratio was 8. A plate with a cross-sectional width of 180 mm and a thickness of 14 mm was extruded from the die, the pushing speed of the hydraulic rod during extrusion was 0.5 mm / s, and the plate was air cooled after extrusion. After preheating at 320 ℃ for 20 minutes, one-way rolling deformation with a pass deformation of 20% was performed, a total of 4 passes, and the rolling direction was parallel to the extrusion direction, until the thickness was reduced to 5.7 mm. After rolling, annealing was performed at 320 ℃ for 10 minutes. The room temperature tensile mechanical properties of the plate along the length (ED) and width (TD) directions are listed in Table 1, and the optical microstructure of the plate is shown in FIG. 1. Figure 3 , and the pole figure and grain orientation diagram of the plate are shown in FIG. 2. Figure 4 .

[0029] Example 3

[0030] An alloy bar with a diameter of Φ160 mm was smelted and semi-continuously cast, and the mass percentage content of the alloy was Mg-3.0Al-1.0Zn-0.1Mn. The ingot was subjected to homogenization annealing treatment, the process was 350 ℃ for 50 h, and then air cooling was performed. The ingot billet after homogenization annealing was cut and blanked to obtain a bar with a diameter of Φ150 mm. The bar and the die were kept at 250 ℃ for 3 h. After the end of the heat preservation, the bar was loaded into the extrusion cylinder for width expansion extrusion, and the extrusion ratio was 16. A plate with a cross-sectional width of 180 mm and a thickness of 7 mm was extruded from the die, the pushing speed of the hydraulic rod during extrusion was 3.5 mm / s, and the plate was air cooled after extrusion. After preheating at 280 ℃ for 30 minutes, one-way rolling deformation with a pass deformation of 30% was performed, a total of 2 passes, and the rolling direction was parallel to the extrusion direction, until the thickness was reduced to 3.4 mm. After rolling, annealing was performed at 280 ℃ for 30 minutes. The room temperature tensile mechanical properties of the plate along the length (ED) and width (TD) directions are listed in Table 1.

[0031] Comparative Example 1

[0032] A Φ160 mm diameter alloy rod was smelted and semi-continuously cast, with the alloy having a mass percentage content of Mg-4.8Al-2.4Zn-0.5Mn. The ingot was subjected to homogenization annealing treatment, with a process of 380°C for 40h, and then taken out and air-cooled. The ingot blank after homogenization annealing was skived and cut, to obtain a Φ150 mm diameter rod. The rod and the die were kept at 280°C for 2h. After the end of the heat preservation, the rod was loaded into the extrusion cylinder for extrusion (without width expansion), with an extrusion ratio of 15.7, to extrude a plate with a cross-sectional width of 135mm and a thickness of 9.5mm from the die mouth, with a hydraulic ram advancing speed of 2mm / s during extrusion, and the plate was air-cooled after extrusion. After preheating at 300°C for 25 minutes, one-way rolling deformation was performed with a pass deformation of 22%, for a total of 2 passes, with the rolling direction parallel to the extrusion direction, until the thickness was reduced to 5.8mm. Annealing was performed at 320°C for 12 minutes after rolling. The room temperature tensile mechanical properties of the plate along the length (ED) and width (TD) directions are listed in Table 1, and the pole figure and grain orientation diagram of the obtained rolled plate are shown in Figures 1 and 2. Figure 5 .

[0033] Comparative Example 2

[0034] A Φ160 mm diameter alloy rod was smelted and semi-continuously cast, with the alloy having a mass percentage content of Mg-4.8Al-2.4Zn-0.5Mn. The ingot was subjected to homogenization annealing treatment, with a process of 380°C for 40h, and then taken out and air-cooled. The ingot blank after homogenization annealing was skived and cut, to obtain a Φ150 mm diameter rod. The rod and the die were kept at 280°C for 2h. After the end of the heat preservation, the rod was loaded into the extrusion cylinder for width expansion extrusion, with an extrusion ratio of 12.1, to extrude a plate with a cross-sectional width of 175mm and a thickness of 9.5mm from the die mouth, with a hydraulic ram advancing speed of 2mm / s during extrusion, and the plate was air-cooled after extrusion. After preheating at 300°C for 25 minutes, one-way rolling deformation was performed with a pass deformation of 10%, for a total of 2 passes, with the rolling direction parallel to the extrusion direction, until the thickness was reduced to 7.7mm. Annealing was performed at 320°C for 12 minutes after rolling. The room temperature tensile mechanical properties of the plate along the length (ED) and width (TD) directions are listed in Table 1, and the pole figure and grain orientation diagram of the obtained rolled plate are shown in Figures 1 and 2. Figure 6 .

[0035] Comparative Example 3

[0036] The alloy bar with a diameter of Φ130 mm is smelted and semi-continuously cast, and the mass percentage content of the alloy is Mg-9.0Al-2.5Zn-0.8Mn. The ingot is subjected to homogenization annealing treatment, and the process is 420 ℃ for 16 h, and then the ingot is taken out and air-cooled. The ingot billet after homogenization annealing is transported and cut, and the bar with a diameter of Φ120 mm is obtained. The bar and the die are kept at 350 ℃ for 1 h. After the keeping, the bar is loaded into an extrusion cylinder for width expansion extrusion, and the extrusion ratio is 8. The plate with a cross-sectional width of 180 mm and a thickness of 14 mm is extruded from the die, and the pushing speed of the hydraulic rod during the extrusion is 0.5 mm / s. After the plate is extruded, the plate is air-cooled. After being preheated at 340 ℃ for 20 minutes, the plate is subjected to unidirectional rolling deformation with a deformation amount of 20%, and the rolling direction is parallel to the extrusion direction, and the thickness is reduced to 5.7 mm after 4 passes. After rolling, the plate is annealed at 320 ℃ for 10 minutes. The room temperature tensile mechanical properties of the plate along the length (ED) and width (TD) directions are listed in Table 1, and the pole figure and the grain orientation diagram of the plate are shown in Figures 1 and 2. Figure 7 .

[0037] Table 1 Mechanical properties of magnesium alloys in examples and comparative examples

[0038]

[0039] From Figure 1 , Figure 3 it can be seen that after the width expansion extrusion and rolling composite forming according to the present application, the plate has small grain size and full recrystallization, which lays a microstructure foundation for excellent comprehensive mechanical properties. In addition, from Figure 2 , Figure 4 it can be known that after the composite forming according to the present application, the plate has typical basal texture characteristics, and the pole point does not deviate from the normal direction (ND) of the plate surface, which can significantly reduce the mechanical property anisotropy of the plate when the plate is stretched along different directions of the plate surface.

[0040] In combination with Figure 2 and Figure 5 , compared with Comparative Example 1 and Example 1, the width expansion extrusion is used in Example 1, and part of the metal will flow along the transverse direction (TD) during the extrusion, so that the mechanical properties of the extruded plate in the TD direction are improved, and the subsequent rolling process is better for improving the mechanical properties in the ED direction, so that the mechanical property anisotropy of the plate after the composite forming is small. However, the width expansion extrusion is not performed in Comparative Example 1, so that the mechanical properties of the extruded plate in the extrusion direction (i.e. the ED direction) are better than those in the TD direction, and the subsequent rolling process further improves the strength in the ED direction, so that the final plate exhibits strong anisotropy.

[0041] In combination with Figure 2 and Figure 6Comparative Example 1 and Comparative Example 2, the rolling pass deformation in Comparative Example 2 is less than the value defined in the claims of the present application, and insufficient rolling deformation results in that the rolled plate fails to form the texture characteristics shown in Figure 2 , the corresponding pole figure and the grain orientation diagram Figure 6 still have the texture component with the basal plane parallel to ND caused by the width expansion extrusion, and the effect of the rolling deformation on the strength improvement of the ED direction is poor, finally resulting in that the TD direction strength is obviously superior to the ED direction, the plate anisotropy is obvious, and the TD direction elongation is less than 12.0%.

[0042] In combination with Figure 4 and Figure 7 , Comparative Example 2 and Comparative Example 3, the preheating temperature before rolling in Comparative Example 3 is too high, the rolling texture will be weakened, resulting in that the rolled plate fails to form the texture characteristics shown in Figure 4 , the corresponding pole figure and the grain orientation diagram Figure 7 still have the texture component with the basal plane parallel to ND caused by the width expansion extrusion, and the effect of the rolling deformation on the strength improvement of the ED direction is still insufficient, finally resulting in that the TD direction strength is obviously superior to the ED direction, the plate anisotropy is obvious, and the TD direction elongation is also less than 12.0%.

[0043] The embodiments of the present application are described above in combination with the drawings, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative but not limiting, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection scope of the present application.

Claims

1. A method of compound processing of a magnesium alloy sheet material, characterized by: The magnesium alloy has the following mass percentage components: Al: 3.0-9.0%, Zn: 1.0-2.5%, Mn: 0.1-0.8%, and the rest is Mg and non-removable impurities, and the preparation process comprises the following steps: A. Smelting and semi-continuous casting a magnesium alloy rod with a diameter of Φ130mm-160mm; B. Homogenizing annealing the ingot; C. Carrying the homogenizing annealed ingot billet and blanking to obtain a rod with a diameter of Φ120mm-150mm; before extrusion, the rod and the die are kept at 250-350℃ for 1-3h; after the keeping, the rod is loaded into an extrusion cylinder for width expansion extrusion with an extrusion ratio of 8-16, and a plate with a cross-sectional width of 160-200mm and a thickness of 7-14mm is extruded from the die; before rolling, the plate is preheated at 280-320℃ for 20-30 minutes; D. Single-direction rolling deformation with a deformation amount of 20-30%, rolling passes are more than twice, the rolling direction is parallel to the extrusion direction, and the thickness is reduced to 3.4-5.8mm; E. Annealing the plate at 280-320℃ for 10-20 minutes after rolling.

2. The composite processing method of the magnesium alloy plate according to claim 1, characterized in that, in step B, the homogenizing annealing process is: keeping at 350-420℃ for 16-50h, and then taking out and air cooling.

3. The composite processing method of the magnesium alloy plate according to claim 1, characterized in that, in step C, the pushing speed of the hydraulic rod during extrusion is 0.5-3.5mm / s; and the plate is air cooled after extrusion.

4. The composite processing method of the magnesium alloy plate according to claim 1, characterized in that, after step E, the plate has a room temperature yield strength of ≥220MPa, a tensile strength of ≥320MPa, and an elongation of ≥12.0% in the transverse and longitudinal directions, and the absolute value of the strength deviation in different directions is less than 15MPa, and the absolute value of the elongation deviation is less than 2%.

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