阅读说明：本技术 一种控制铝基复合材料晶须定向排布的锻造方法 (forging method for controlling directional arrangement of aluminum matrix composite whiskers ) 是由 徐文臣 徐佳炜 单德彬 靳学泽 杨国静 于 2019-09-06 设计创作，主要内容包括：本发明提供了一种控制铝基复合材料晶须定向排布的锻造方法,属于等温锻造技术领域。本发明所述的锻造方法包括以下步骤：对铝基复合材料铸坯的轴向和径向进行近等温交替镦粗；每次镦粗的压下量为15％～35％；所述近等温交替镦粗过程中始终保持径向一致。本发明对铝基复合材料铸坯的轴向和径向进行近等温交替镦粗,使得材料中晶须伴随着基体变形流动改变排布,镦粗过程中,由于始终保持镦粗的径向一致,晶须主要沿着未经过锻造的方向排列,从而实现定向排布；通过控制每次镦粗的压下量,保证坯料在锻造过程中不会出现开裂等缺陷,且可实现较大尺寸锻件的晶须定向排布设计,提高特定方向的弹性模量,以改善其承载性能。(The invention provides a forging method for controlling directional arrangement of whiskers of an aluminum-based composite material, belonging to the technical field of isothermal forging. The forging method comprises the following steps: carrying out near isothermal alternative upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction; the reduction of each upsetting is 15 to 35 percent; the radial consistency is always kept in the process of the near isothermal alternative upsetting. The method carries out near isothermal alternative upsetting on the axial direction and the radial direction of the aluminum matrix composite casting blank, so that the arrangement of whiskers in the material is changed along with the deformation and the flow of a matrix; by controlling the reduction of each upsetting, the blank is ensured not to have the defects of cracking and the like in the forging process, the directional distribution design of the whiskers of the large-size forging can be realized, and the elastic modulus in a specific direction is improved so as to improve the bearing performance of the forging.)

1. A forging method for controlling directional arrangement of aluminum matrix composite whiskers is characterized by comprising the following steps: carrying out near isothermal alternative upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction; the reduction of each upsetting is 15 to 35 percent independently; the radial consistency is always kept in the process of the near isothermal alternative upsetting.

2. The forging method as recited in claim 1, wherein the total number of upsetting is 6 to 12.

3. The forging method as recited in claim 2, wherein a cumulative nominal strain after the near-isothermal alternating upsetting is 1.5 to 3.0.

4. The forging method as recited in claim 1, wherein the aluminum-based composite material is a silicon carbide whisker-reinforced aluminum-based composite material or an aluminum borate whisker-reinforced aluminum-based composite material.

5. The forging method as recited in claim 4, wherein the volume fraction of whiskers in the aluminum matrix composite material is 15 to 30%, and the length of whiskers is 10 to 60 μm.

6. The forging method as recited in claim 1 or 4, wherein the aluminum-based composite material ingot is cylindrical.

7. The forging method as recited in claim 1, wherein the apparatus used for the near-isothermal alternative upsetting is a press, and a reduction rate of an anvil on the press is 6 to 15 mm-s ^-1.

8. The forging method as recited in claim 7, wherein the upper and lower anvils of the press are heated to a temperature 0 to 20 ℃ lower than that of the cast slab of the aluminum matrix composite material before the near-isothermal alternate upsetting.

9. The forging method as recited in claim 8, wherein the temperature of the aluminum matrix composite material ingot is 410 to 480 ℃.

10. the forging method as recited in claim 1, further comprising, after the near-isothermal alternating upsetting, air-cooling the upset aluminum matrix composite material to room temperature.

Technical Field

The invention relates to the technical field of isothermal forging, in particular to a forging method for controlling directional arrangement of whiskers of an aluminum-based composite material.

Background

The metal matrix composite material has great application potential in manufacturing light-weight high-performance components due to excellent properties (such as low density, high specific strength and specific rigidity, excellent wear resistance and the like). Among a plurality of metal matrix composite materials, the aluminum matrix composite material is the most widely used one, mainly because the aluminum alloy is a face-centered cubic structure, has 12 slip systems, has good ductility and toughness, has the advantages of low price, easy processing and the like, and the aluminum matrix composite material is gradually applied to the fields of aerospace and the like at present.

The aluminum-based composite material prepared by adopting the extrusion casting method has the casting defects of looseness, holes and the like, different whisker lengths, irregular orientation, less whisker agglomeration, narrow-strip-shaped holes between partial whiskers and a matrix and the like, cannot prepare an aluminum-based composite material finished product meeting the requirements on the appearance size, the mechanical property and the like at one time, and needs to be subjected to secondary processing. In the secondary processing method of the cast aluminum-based composite material, the thermoplastic deformation can forge loose and hole defects, refine crystal grains and uniformly distribute whiskers, thereby improving the mechanical property of the composite material, and the secondary processing method is widely applied. In addition, for the whisker reinforced aluminum matrix composite, the directional arrangement of the whiskers is helpful for improving the mechanical property of the component in a specific direction and meeting the service requirement of the component under a specific condition. The existing common thermoplastic deformation method is a hot extrusion method, and the whiskers can be directionally arranged along the extrusion direction by adopting a hot extrusion process on an as-cast blank, but the extrusion process has the disadvantages of complex die and high cost, and a large-tonnage extruder is usually required for a large-section blank, so that the equipment cost is high.

Disclosure of Invention

The invention aims to provide a forging method for controlling the directional arrangement of whiskers of an aluminum-based composite material, which is simpler and lower in cost compared with a hot extrusion process.

In order to achieve the above object, the present invention provides the following technical solutions:

The invention provides a forging method for controlling directional arrangement of whiskers of an aluminum-based composite material, which comprises the following steps of: carrying out near isothermal alternative upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction; the reduction of each upsetting is 15 to 35 percent independently; the radial consistency is always kept in the process of the near isothermal alternative upsetting.

Preferably, the total number of upsetting is 6 to 12.

Preferably, after the near isothermal alternating upsetting, the accumulated nominal strain is 1.5-3.0.

Preferably, the aluminum matrix composite is a silicon carbide whisker reinforced aluminum matrix composite or an aluminum borate whisker reinforced aluminum matrix composite.

Preferably, the volume fraction of the whiskers in the aluminum matrix composite material is 15-30%, and the length of the whiskers is 10-60 μm.

Preferably, the aluminum matrix composite casting blank is cylindrical.

preferably, when the near isothermal alternative upsetting is carried out, the adopted equipment is a press, and the pressing speed of an upper anvil of the press is 6-15 mm s ^-1.

Preferably, before the near isothermal alternative upsetting, the upper anvil and the lower anvil of the press are heated to be 0-20 ℃ lower than the temperature of the aluminum matrix composite casting blank.

preferably, the temperature of the aluminum matrix composite casting blank is 410-480 ℃.

Preferably, after the near isothermal alternative upsetting, the upsetting obtained aluminum matrix composite material is cooled to room temperature by air.

The invention provides a forging method for controlling directional arrangement of whiskers of an aluminum-based composite material, which comprises the following steps of: carrying out near isothermal alternative upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction; the reduction of each upsetting is 15-35%, and the radial consistency is always kept in the process of the near isothermal alternating upsetting. The method carries out near isothermal alternative upsetting on the axial direction and the radial direction of the aluminum matrix composite casting blank, so that the arrangement of whiskers in the material is changed along with the deformation and the flow of a matrix; by controlling the reduction of each upsetting, the blank is ensured not to have the defects of cracking and the like in the forging process, the directional arrangement design of the whiskers of the large-size forging can be realized, and the elastic modulus in a specific direction is improved, so that the bearing performance of the aluminum matrix composite material is improved.

drawings

FIG. 1 is a schematic view of a forging method according to the present invention;

FIG. 2 is a photograph of an aluminum-based composite material blank before forging and after forging in accordance with example 1;

FIG. 3 is a scanning metallographic photograph showing a section of the aluminum matrix composite YOZ of example 1 at 5000 times before forging;

FIG. 4 is a scanning metallographic photograph showing a section of the forged aluminum matrix composite YOZ at 5000 times in example 1;

FIG. 5 is a graph of the tensile true strain in the Y-direction and the Z-direction of the two-way forging of the aluminum matrix composite of example 1;

FIG. 6 is an aluminum matrix composite forging prepared in example 2;

FIG. 7 is a graph of the true tensile strain in the Y-direction and Z-direction of the two-way forging of the aluminum matrix composite of example 2.

Detailed Description

The invention provides a forging method for controlling directional arrangement of whiskers of an aluminum-based composite material, which comprises the following steps of: carrying out near isothermal alternative upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction; the reduction of each upsetting is 15 to 35 percent independently; the radial consistency is always kept in the process of the near isothermal alternative upsetting.

In the invention, the near isothermal alternative upsetting means that the aluminium matrix composite material casting blank is subjected to two-way alternative upsetting in the axial direction and a certain radial direction under the near isothermal condition, and the near isothermal condition means that the temperature of the aluminium matrix composite material casting blank is approximately equal to the temperature of a pressed piece contacted with the aluminium matrix composite material casting blank.

In the present invention, the aluminum matrix composite is preferably a silicon carbide whisker reinforced aluminum matrix composite or an aluminum borate whisker reinforced aluminum matrix composite; the volume fraction of the whiskers in the aluminum matrix composite material is preferably 15-30%, the length of the whiskers is preferably 10-60 mu m, more preferably 20-60 mu m, and even more preferably 30-60 mu m. The invention has no special requirements on the composition of the aluminum-based material in the aluminum-based composite material, and the aluminum-based material with the composition is well known to those skilled in the art. In the present invention, the shape of the aluminum-based composite material ingot is preferably cylindrical. The invention preferably prepares the aluminum-based composite material casting blank by an extrusion casting process. The extrusion casting process conditions of the invention have no special requirements, and the extrusion casting process conditions well known in the art can be adopted. In the embodiment of the invention, the whisker preform is preferably preheated, then an aluminum alloy melt (i.e. an aluminum-based material melt) is cast, and after the aluminum alloy melt is maintained under a certain pressure for a certain time, an aluminum-based composite material casting blank is obtained. The source of the whisker preform is not particularly required, and the whisker preform can be prepared according to a method known in the field. In the invention, the pressure for pressure maintaining is preferably 40-60 MPa, and the time for pressure maintaining is preferably 20-30 min.

The method preferably adopts a press to carry out alternate upsetting on the aluminum matrix composite casting blank in the axial direction and the radial direction, the reduction rate of an upper anvil of the press is preferably 6-15 mm s ^-1, more preferably 8-12 mm s ^-1, and a lower anvil of the press is preferably fixed in the upsetting process.

Before the near isothermal alternative upsetting, the upper anvil and the lower anvil of the press are preferably heated to be 0-20 ℃ lower than the temperature of the aluminum matrix composite casting blank, and more preferably 0-10 ℃ lower than the temperature of the aluminum matrix composite casting blank. In the invention, the temperature of the aluminum-based composite material casting blank is preferably 410-480 ℃, and the heat preservation time after the temperature reaches the specified temperature is preferably 60-150 min, and further preferably 80-120 min. The invention has no special requirements on the heating modes of the aluminum matrix composite casting blank and the upper anvil and the lower anvil, and the heating mode which is well known by the technical personnel in the field can be adopted. Because the aluminum-based composite material casting blank is heated and then transferred between the upper anvil and the lower anvil for forging, part of heat is dissipated in the transfer process, and in order to keep the temperature of the aluminum-based composite material casting blank consistent with the temperature of the upper anvil and the lower anvil as far as possible, the temperature of the aluminum-based composite material casting blank is set to be 0-20 ℃ higher than the temperature of the upper anvil and the lower anvil.

Meanwhile, the reduction speed of the upper anvil is high, so that the target reduction can be achieved before the temperature of the aluminum-based composite material casting blank is obviously reduced, the forging process can be completed in a short time, and the temperature of the upper anvil and the temperature of the lower anvil are approximately the same as the temperature of the aluminum-based composite material casting blank in the forging process. The invention adopts a forging mode of near isothermal, thereby avoiding the performance reduction of the blank caused by uneven temperature and uneven deformation flow of the casting blank due to temperature reduction.

in the invention, when the near isothermal alternative upsetting is carried out, the reduction of each upsetting is independently 15-35%, preferably 20-30%; the total upsetting times are preferably 6-12 times, and more preferably 6-9 times; after the near isothermal alternating upsetting, the accumulated nominal strain is preferably 1.5 to 3.0, and more preferably 1.8 to 2.5. In the present invention, the cumulative nominal strain refers to the cumulative sum of the reduction per upset in both the axial and radial directions. The reduction per upset referred to in the present invention means reduction relative to the thickness of the cast slab before the next upset, and for example, when the height of the slab before the upset is 10cm and the height after the upset is 8cm, the reduction is 20%.

the forging method of the present invention will be described with reference to fig. 1 as an example. The method comprises the steps of firstly upsetting along the axial direction (namely the Z direction) of an aluminum-based composite material casting blank, wherein the reduction along the axial direction is 15-35%, then upsetting along the radial direction (namely the X direction) is 15-35%, then upsetting along the axial direction (namely the Z direction) is 15-35%, then upsetting along the same radial direction (namely the X direction) is 15-35%, and finally upsetting along the X direction is 15-35%, and the upsetting and the aluminum-based composite material casting blank alternately until the required accumulated nominal strain is achieved.

The method carries out near isothermal alternative upsetting on the aluminum matrix composite material in the axial direction and the radial direction, keeps the radial consistency all the time in the upsetting process, leads the whiskers in the material to change the arrangement along with the deformation and the flow of the matrix, and leads the whiskers to be mainly arranged along the direction which is not forged in the upsetting process, thereby realizing the directional arrangement; when forged as shown in FIG. 1, the whiskers are mainly arranged in the Y direction; the invention can prevent the blank from cracking and other defects in the forging process by controlling the reduction of each upsetting in the range, can realize the oriented arrangement design of the whiskers of the forging with larger size, and improves the elastic modulus in a specific direction so as to improve the bearing performance of the forging.

After the alternating upsetting is completed, the invention preferably further comprises air cooling the composite material obtained by upsetting to room temperature.

the forging method for controlling the orientation arrangement of the whiskers of the aluminum-based composite material provided by the invention is described in detail below with reference to the following examples, but the method is not to be construed as limiting the scope of the invention.