CN111926271A

CN111926271A - Processing method for improving in-plane isotropy of aluminum matrix composite

Info

Publication number: CN111926271A
Application number: CN202010892803.8A
Authority: CN
Inventors: 赵乃勤; 戎旭东; 何春年; 师春生; 刘恩佐; 赵冬冬
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2020-11-13

Abstract

The invention relates to a processing method for improving in-plane isotropy of an aluminum matrix composite, which comprises the following steps: (1) machining a sample to be rolled; (2) orthogonal rolling deformation: and (3) placing the block to be rolled in a liquid nitrogen environment for heat preservation for a period of time, performing primary rolling along one direction, placing the sample in the liquid nitrogen environment again for heat preservation for a period of time after rolling, tilting for 90 degrees in the horizontal direction, then performing rolling, keeping the single rolling amount unchanged, and repeating the steps in such a circulating way until the total rolling amount of the sample is 50-70%. (3) And annealing the rolled sample.

Description

Processing method for improving in-plane isotropy of aluminum matrix composite

Technical Field

The invention relates to a processing method for improving in-plane isotropy of an aluminum-based composite material by using a low-temperature orthogonal rolling-annealing process, belonging to the technical field of preparation of metal-based composite materials.

Background

The aluminum-based composite material has the advantages of high specific strength and specific modulus, good electric and heat conductivity and the like, and has wide application requirements in the fields of aerospace and civil use. Composite materials prepared by casting or powder metallurgy methods generally have the disadvantage of low compactness, and therefore the mechanical properties are further improved by extrusion or rolling. However, the deformation process can increase the strength, but also results in severe anisotropy of the material, i.e. along the deformation direction, the tensile strength of the composite material is significantly increased, and the plastic deformability is reduced. Taking the in-situ alumina reinforced aluminum alloy matrix composite prepared by the powder metallurgy method as an example, the particles or grains of the composite after hot extrusion and deformation are elongated into fiber shape along the extrusion direction (as shown in figure 1 (a)), and the texture orientation is obvious (as shown in figure 1 (b)). In practical engineering application, except for special components, the material structure performance is required to be uniform and stable, which puts higher requirements on the processing deformation process.

Disclosure of Invention

Aiming at the defect that the anisotropy of the mechanical property in the surface of the processed composite material is obvious, the invention aims to provide a novel process of low-temperature orthogonal rolling-annealing treatment, which is used for improving the isotropy of the composite material. The technical scheme is as follows:

a processing method for improving the in-plane isotropy of an aluminum matrix composite comprises the following steps:

(1) machining a sample to be rolled;

(2) cross rolling deformation

And (3) placing the block to be rolled in a liquid nitrogen environment for heat preservation for a period of time, performing primary rolling along one direction, placing the sample in the liquid nitrogen environment again for heat preservation for a period of time after rolling, tilting for 90 degrees in the horizontal direction, then performing rolling, keeping the single rolling amount unchanged, and repeating the steps in such a circulating way until the total rolling amount of the sample is 50-70%.

(3) And annealing the rolled sample.

Preferably, in the step (2), the amount of single rolling is 5-10% of the total thickness of the sample. The total pricking amount of the sample is 50-70%. In the step (3), the annealing temperature is 80-150 ℃, and the annealing treatment time is 1-2 h.

Low temperature cross rolling-annealing mechanism:

after the unidirectional rolling treatment, the particles or grains of the composite material are elongated along the rolling direction, and the sample is tilted by 90 degrees before the next rolling, so that the microstructure of the composite material can be stretched along the vertical direction of the previous rolling direction, and the uniform deformation of the microstructure is ensured as much as possible. Meanwhile, the cold-working deformation mode is rolled at low temperature, so that a large amount of deformation energy and dislocation are accumulated in a composite material sample. After the subsequent annealing treatment, the composite material is fully recrystallized, so that the composite material with excellent density and uniform and stable tissue is obtained.

The rolling process provided by the invention can effectively improve the defects of the in-plane microstructure and the anisotropy of mechanical properties of the composite material. Compared with the existing hot working process, the composite material processed by the method has greatly improved tissue uniformity, and meanwhile, for the processed sample, tensile samples are respectively taken along the directions of 0 degree, 45 degrees and 90 degrees in the processing direction in a plane, and the tensile result shows that the composite material has better isotropy (the difference of the tensile strength of the samples with different orientations is less than 25MPa, and the difference of the elongation at break is less than 1%).

Drawings

FIG. 1 microstructure of extruded composite material (a) scanning the image shows particles and grains as fibers along the extrusion direction; (b) an orientation profile;

FIG. 2 is a flow chart of a low temperature cross rolling process;

FIG. 3 is a microstructure of the composite after low temperature cross rolling-annealing treatment;

FIG. 4 is a graph of tensile properties of composites of different orientations in-plane after low temperature cross rolling-annealing treatment.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting.

Example 1

The powder metallurgy sintered composite material is subjected to wire cutting processing, and the size of a sample to be rolled is 20mm x 10mm x 4 mm. After heat preservation is carried out for 10min in a liquid nitrogen environment, rolling is carried out along the length direction of the sample, and the single rolling amount is 5%. And tilting the rolled sample by 90 degrees along the horizontal direction, and then performing the second pass of rolling, wherein the rolling amount is also 5 percent, and the total rolling amount circulated until the sample is 50 percent. Annealing at 120 deg.C for 1.5 h. The process flow of the low temperature cross rolling is shown in fig. 2. The microstructure morphology is shown in fig. 3, and the grain boundaries or grain boundaries of the sample are nearly equiaxed (fig. 3(a)), while the different grains do not exhibit a distinct preferred orientation (fig. 3 (b)). Three groups of samples which are 0 degrees, 45 degrees and 90 degrees with the initial rolling direction are respectively taken on a horizontal plane for tensile property test of the rolled sample, the mechanical property is shown as figure 4, the difference of the tensile strength in different directions is less than 25MPa, and the difference of the elongation at break is less than 1%.

Example 2

The powder metallurgy sintered composite material is subjected to wire cutting processing, and the size of a sample to be rolled is 20mm x 20mm x 5 mm. After heat preservation is carried out for 10min in a liquid nitrogen environment, rolling is carried out along the length direction of the sample, and the single rolling amount is 5%. And (3) tilting the rolled sample by 90 degrees along the horizontal direction, preserving heat in liquid nitrogen for 10min, and then performing second-pass rolling, wherein the rolling amount is also 5 percent, and the process is circulated until the total rolling amount of the sample is 50 percent. Annealing at 120 ℃ for 2 h. And (3) respectively taking three groups of samples which are 0 degrees, 45 degrees and 90 degrees with the initial rolling direction on a horizontal plane after the rolling to perform tensile property test.

Example 3

The powder metallurgy sintered composite material is subjected to wire cutting processing, and the size of a sample to be rolled is 15mm x 15mm x 4 mm. After heat preservation is carried out for 10min in a liquid nitrogen environment, rolling is carried out along the length direction of the sample, and the single rolling amount is 6%. And (3) tilting the rolled sample by 90 degrees along the horizontal direction, preserving heat in liquid nitrogen for 10min, and then performing second-pass rolling, wherein the rolling amount is also 6 percent, and the process is circulated until the total rolling amount of the sample is 60 percent. Annealing at 120 deg.C for 1.5 h. And (3) respectively taking three groups of samples which are 0 degrees, 45 degrees and 90 degrees with the initial rolling direction on a horizontal plane after the rolling to perform tensile property test.

Example 4

The powder metallurgy sintered composite material is subjected to wire cutting processing, and the size of a sample to be rolled is 10mm x 10mm x 4 mm. After heat preservation is carried out for 10min in a liquid nitrogen environment, rolling is carried out along the length direction of the sample, and the single rolling amount is 5%. And (3) tilting the rolled sample by 90 degrees along the horizontal direction, preserving heat in liquid nitrogen for 10min, and then performing second-pass rolling, wherein the rolling amount is also 5 percent, and the process is circulated until the total rolling amount of the sample is 60 percent. Annealing at 120 ℃ for 2 h. And (3) respectively taking three groups of samples which are 0 degrees, 45 degrees and 90 degrees with the initial rolling direction on a horizontal plane after the rolling to perform tensile property test.

Claims

1. A processing method for improving the in-plane isotropy of an aluminum matrix composite comprises the following steps:

(1) machining a sample to be rolled;

(2) cross rolling deformation

(3) And annealing the rolled sample.

2. The processing method according to claim 1, wherein in the step (2), the amount of single rolling is 5-10% of the total thickness of the sample.

3. The process of claim 1, wherein in step (2), the total rolling amount of the sample is 50 to 70%.

4. The processing method according to claim 1, wherein in the step (3), the annealing temperature is 80 to 150 ℃ and the annealing treatment time is 1 to 2 hours.