CN114214551B - A kind of preparation method of low anisotropy high plasticity magnesium alloy - Google Patents

Abstract

The invention discloses a preparation method of a low-anisotropy high-plasticity magnesium alloy, which comprises the steps of carrying out homogenization, hot extrusion and one-time cold rolling treatment along the extrusion direction on a Mg-Zn-Ce ternary alloy cast ingot in sequence to obtain the low-anisotropy high-plasticity magnesium alloy. Wherein, the extruded magnesium alloy blank is of a bimodal texture type, and the annealed magnesium alloy is of a ring texture type. The anisotropy of the mechanical property of the wrought magnesium alloy can be effectively weakened only by one-time cold rolling and 1-time annealing in the whole rolling forming process, the prepared high-plasticity magnesium alloy has excellent performance, particularly has higher plasticity along the rolling direction and the direction vertical to the rolling direction and basically keeps consistent, the plasticity is up to 43 percent, the anisotropy of the magnesium alloy can be effectively weakened while the plasticity of the alloy is improved, the subsequent large deformation and cold processing are facilitated, the potential of the magnesium alloy as an engineering component material is greatly improved, and the engineering field of possible application of the magnesium alloy is expanded.

Description

A kind of preparation method of low anisotropy and high plasticity magnesium alloy

technical field

The invention relates to the field of manufacture of magnesium alloy materials, in particular to a preparation method of a low anisotropy and high plasticity magnesium alloy.

Background technique

As a green light metal structural material in the 21st century, magnesium alloys have made outstanding contributions to energy conservation, emission reduction and environmental protection. Compared with cast magnesium alloys, wrought magnesium alloys have a wider range of applications. However, due to the lower crystal symmetry of magnesium, the It is easy to produce deformation texture during the deformation process, resulting in obvious plastic anisotropy, which limits its further deformation processing. Therefore, the preparation of high-plastic magnesium alloys with low anisotropy is of great strategic significance for promoting the large-scale application of wrought magnesium alloys.

At present, there are a variety of processes to eliminate the anisotropy of magnesium alloys at home and abroad, such as asynchronous rolling, equal diameter angle rolling, cross rolling and unidirectional repeated bending deformation, etc., but these methods are relatively complex and technically difficult. High, unable to produce large-scale bulk materials. The multi-directional forging process is repeated upsetting and elongation of magnesium alloy billets from different directions. After each pass of deformation, it is returned to the furnace for annealing. The purpose is to reduce residual stress and refine grains through static recrystallization to improve plasticity. Control the holding time well to prevent serious grain growth. Because the grain refinement increases the surface area of the grain boundary, the "grain boundary sliding deformation mechanism" accounts for a large enough amount in the total deformation, except for the basal plane slip and Beyond twinning, the slip of a large number of grain boundaries coordinates the deformation, thereby weakening the texture. Therefore, multi-directional forging can effectively weaken the "mechanical property anisotropy" of deformed magnesium alloys as a blanking method, and it is also a commonly used method now. However, in the process of multi-directional forging, it is necessary to strictly control the amount of deformation, and adopt multi-pass commutation forging with small deformation amount to ensure the formability and mechanical properties of the material while avoiding the formation of strong basal texture, which leads to complex process and technical requirements. Staff requirements are high. It is precisely because most of the cast magnesium alloys have poor room temperature plasticity, which is not conducive to one-time large plastic deformation during the rolling process, so there is no report on the realization of low anisotropy of magnesium alloys by one-step cold rolling.

SUMMARY OF THE INVENTION

In view of the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a preparation method of a low-anisotropy and high-plasticity magnesium alloy, so as to solve the problem that the existing method has complicated processes, requires multi-directional forging, and is relatively technically difficult. higher issues.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: a preparation method of a low anisotropy and high plasticity magnesium alloy, comprising the following steps:

1) homogenizing the magnesium alloy ingot, air-cooling to room temperature, to obtain a magnesium alloy billet, and the magnesium alloy is a Mg-Zn-Ce ternary alloy;

2) Preheat the homogenized magnesium alloy billet to 450-460°C, then put it into an extrusion cylinder for hot extrusion in an extruder, and the obtained extruded magnesium alloy billet exhibits a bimodal texture type;

3) The extruded billet is subjected to one pass of cold rolling along the extrusion direction, and the pass reduction is 5-20%, and then annealed to obtain a ring-shaped texture type of the magnesium alloy, which is the low isotropic Anisotropic high plasticity magnesium alloy.

In this way, excessive deformation in a single pass will form a strong basal texture during the forging process, resulting in obvious anisotropy in the mechanical properties of the product, and at the same time increasing the risk of ingot cracking. Too low deformation is easy to cause excessive grain growth and affect the mechanical properties of the product.

Preferably, the magnesium alloy includes the following components by mass percentage: 0.5-3% of Zn, 0.1-0.5% of Ce, and the rest are magnesium and irremovable impurity elements.

Preferably, the homogenization treatment is maintained at 470-480° C. for 18-19 hours.

Preferably, the reduction amount of the one-stage cold rolling is 8%.

Preferably, the reduction amount of the one-stage cold rolling is 19%.

Preferably, the hot extrusion temperature is 420-450°C.

Preferably, the extrusion speed is 1-2 mm/min, and the extrusion ratio is 28-30:1.

Preferably, the annealing temperature is 350-360° C., and the time is 1-2 h.

Another object of the present invention is to provide a low anisotropy and high plasticity magnesium alloy prepared by the above method.

Another object of the present invention is to provide the application of the above-mentioned low anisotropy and high plasticity magnesium alloy in engineering structural materials.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention selects the Mg-Zn-Ce ternary alloy as the raw material. After the optimized extrusion process, the magnesium alloy shows a bimodal texture type, and after the optimized cold rolling annealing process, the magnesium alloy shows a ring texture type. Among them, relatively low deformation of the pass is adopted, and the deformation of the pass is controlled within 5-20%, so as to avoid the formation of strong basal texture during the deformation process, and at the same time to ensure that the entire rolling forming process only needs to be carried out once. Cold rolling and one-time annealing can effectively weaken the anisotropy of mechanical properties of the deformed magnesium alloy, and solve the problems of complicated process and high technical difficulty of the existing method.

2. The high plasticity magnesium alloy prepared by the present invention has excellent properties, especially the plasticity along the rolling direction and perpendicular to the rolling direction is relatively high and basically consistent, up to 42%, which can effectively weaken the plasticity of the alloy while improving the plasticity. The anisotropy of magnesium alloys is beneficial to subsequent large deformation and cold working, which greatly enhances their potential as engineering component materials, expands the engineering field of magnesium alloys' possible applications, and also provides research on high plasticity and low anisotropy magnesium alloys. It provides a theoretical basis and is of great significance.

3. The equipment used in the present invention is simple, the content of alloy elements is low, the cost is low, the processing technology is simple and convenient to operate, and it is easy to industrialize large-scale production.

Description of drawings

FIG. 1 is the pole figure of the as-extruded state (a) and the annealed state (b) of the magnesium alloy prepared in Example 3. FIG.

FIG. 2 is a strain curve diagram of tensile mechanical properties at room temperature of the magnesium alloy prepared in Example 3. FIG.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples.

One, a kind of preparation method of low anisotropy high plasticity magnesium alloy

Example 1

1) Select a magnesium alloy ingot Mg-1%wtZn-0.3%wtCe ternary alloy, homogenize it at 480°C for 18h, and air-cool it to room temperature to obtain a magnesium alloy billet.

2) Preheat the homogenized magnesium alloy billet to 450-460°C, and then put it into the extrusion cylinder for hot extrusion in the extruder, the extrusion temperature is 450°C, the extrusion ratio is 30:1, and the extrusion After pressing, the blank is 56mm wide and 3mm thick.

3) The extruded billet is subjected to one pass of cold rolling along the extrusion direction, the pass reduction is 5%, and then annealed, the annealing temperature is 350 ° C, and the annealing time is 1h, which is the low anisotropy and high. Plastic magnesium alloy.

The magnesium alloy obtained in this example has an ultimate tensile strength at room temperature along the RD (rolling direction) direction of 239 MPa, a tensile elongation after fracture of 32.6%, and a room temperature ultimate tensile strength along the TD (longitudinal direction of the rolled piece) direction of 256 MPa. The elongation after breaking was 23.2%.

Example 2

1) Select a magnesium alloy ingot Mg-1%wtZn-0.3%wtCe ternary alloy, homogenize it at 480°C for 18h, and air-cool it to room temperature to obtain a magnesium alloy billet.

2) Preheat the homogenized magnesium alloy billet to 450-460°C, and then put it into the extrusion cylinder for hot extrusion in the extruder, the extrusion temperature is 450°C, the extrusion ratio is 30:1, and the extrusion ratio is 30:1. After pressing, the blank is 56mm wide and 3mm thick.

3) The extruded billet is subjected to one pass of cold rolling along the extrusion direction, the pass reduction is 8%, and then annealed, the annealing temperature is 350 ° C, and the annealing time is 1h, which is the low anisotropy and high. Plastic magnesium alloy.

The magnesium alloy obtained in this example has an ultimate tensile strength at room temperature along the RD (rolling direction) direction of 233 MPa, a tensile elongation after fracture of 42.2%, and a room temperature ultimate tensile strength along the TD (longitudinal direction of the rolled piece) direction of 245 MPa. The elongation after breaking was 37.2%.

Example 3

1) Select a magnesium alloy ingot Mg-1%wtZn-0.3%wtCe ternary alloy, homogenize it at 480°C for 18h, and air-cool it to room temperature to obtain a magnesium alloy billet.

2) Preheat the homogenized magnesium alloy billet to 450-460°C, and then put it into the extrusion cylinder for hot extrusion in the extruder, the extrusion temperature is 450°C, the extrusion ratio is 30:1, and the extrusion After pressing, the blank is 56mm wide and 3mm thick.

3) The extruded billet is subjected to one pass of cold rolling along the extrusion direction, the pass reduction is 19%, and then annealed, the annealing temperature is 350 ° C, and the annealing time is 1h, which is the low anisotropy and high. Plastic magnesium alloy.

The magnesium alloy obtained in this example has an ultimate tensile strength at room temperature along RD (rolling direction) of 228 MPa, a tensile elongation after fracture of 41.6%, and an ultimate tensile strength at room temperature along the TD (longitudinal direction of the rolled piece) direction of 221 MPa, and the tensile strength is 221 MPa. The elongation after breaking was 45.4%.

EBSD observation and analysis were carried out on the magnesium alloys in the extrusion state and rolling annealing state in this example, and the results are shown in FIG. 1 .

It can be seen from FIG. 1 that the extruded magnesium alloy billet of the present invention exhibits a bimodal texture type, and the rolled and annealed magnesium alloy exhibits a ring texture type.

The low anisotropy and high plasticity magnesium alloy prepared in this example was tested for tensile mechanical properties at room temperature, and the results are shown in FIG. 2 .

It can be seen from FIG. 2 that the average elongation after fracture of the magnesium alloy obtained by the present invention is as high as 43%, and the anisotropy is low.

To sum up, the high plasticity magnesium alloy prepared by the present invention has excellent properties, especially the plasticity along the rolling direction and perpendicular to the rolling direction is relatively high and basically consistent, up to 43%. This is due to the fact that when the hexagonal close-packed magnesium alloy is deformed at room temperature, the basal plane slip has the lowest critical shear stress so that it dominates the plastic deformation process, and the as-extruded magnesium alloy exhibits deflection along the ED. When rolling along the extrusion direction, the Schmidt factor of the basal plane slip shows a maximum value, which is very beneficial to the basal plane slip, so that a large one-time cold rolling can be carried out. Sufficient dislocation density and strain energy are stored to allow static recrystallization of the alloy during subsequent annealing. In addition, the Mg-Zn-Ce alloy has a preferential growth of the TD texture component during the static recrystallization process, while retaining part of the RD texture component while increasing the proportion of the TD texture component, making it possible to increase the proportion of the TD texture component during the first annealing process. The annular texture is then achieved. Therefore, the present invention only needs to perform one cold rolling and one annealing in the whole rolling forming process, so that the mechanical property anisotropy of the deformed magnesium alloy can be effectively weakened.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (6)

1. The preparation method of the low-anisotropy high-plasticity magnesium alloy is characterized by comprising the following steps of:

1) Homogenizing a magnesium alloy ingot, and cooling the magnesium alloy ingot to room temperature by water to obtain a magnesium alloy blank, wherein the magnesium alloy comprises the following components in percentage by mass: 0.5 to 3 percent of Zn, 0.1 to 0.5 percent of Ce, and the balance of magnesium and non-removable impurity elements;

2) Preheating the magnesium alloy blank subjected to homogenization treatment to 450-460 ℃, then putting the magnesium alloy blank into an extrusion cylinder, and carrying out hot extrusion on the magnesium alloy blank in an extrusion machine to obtain an extruded magnesium alloy blank with a bimodal texture type;

3) Carrying out one-time cold rolling on the extruded blank along the extrusion direction, wherein the pass reduction is 5-20%, and then carrying out annealing treatment to obtain the magnesium alloy which is in a ring texture type, namely the low-anisotropy high-plasticity magnesium alloy;

the homogenization treatment is carried out at 470 to 480 ℃ for 18 to 19h; the hot extrusion temperature is 420 to 450 ℃, the extrusion speed is 1 to 2mm/min, and the extrusion ratio is 28 to 30:1; the annealing temperature is 350-360 ℃, and the time is 1-2h.

2. The method for preparing the low-anisotropy high-plasticity magnesium alloy according to claim 1, wherein the reduction amount of the single-pass cold rolling is 8%.

3. The method for preparing the low-anisotropy high-plasticity magnesium alloy according to claim 1, wherein the reduction amount of the one-pass cold rolling is 19%.

4. The method for preparing the magnesium alloy with low anisotropy and high plasticity as claimed in claim 1, wherein the extruded magnesium alloy billet is 54 to 56mm wide and 2 to 3mm thick.

5. A magnesium alloy with low anisotropy and high plasticity prepared by the method as claimed in any one of claims 1 to 4.

6. The use of the low-anisotropy high-plasticity magnesium alloy according to claim 5 in engineering structural materials.

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