CN101333583A - A kind of preparation method of fine-grained superplastic material with short process - Google Patents

Abstract

Disclosed is a process for preparing short process fine crystalline superplasticity materials, which is characterized in that: cast alloy is used as a starting material for carrying out the agitation and friction processing after the homogenization heat treatment, and a bulky, loose and uneven cast structure is changed into an even and compact fine crystalline superplasticity structure.

Description

A kind of preparation method of fine-grained superplastic material with short process

Technical field:

The invention relates to metal materials, and in particular provides a preparation method of a short-flow fine-grained superplastic material, which is suitable for processing aluminum alloys, magnesium alloys, zinc alloys, and copper alloys.

Background technique:

Superplasticity has gradually developed into a mature overall industrial component forming process, which is widely used in automotive, aviation and other industrial fields. Traditionally, the preparation of fine-grain superplastic aluminum alloys adopts thermomechanical processing methods, involving overaging treatment, multi-pass warm rolling, recrystallization treatment and other processes, which are complicated and costly.

Friction stir processing is a new plastic processing technology for metal materials developed on the basis of the basic principles of friction stir welding. Compared with other plastic processing techniques, the friction stir processing process is simple, and the microstructure can be refined in one step. Using this technology, fine-grained superplastic structures have been obtained in several commercial aluminum alloys, and good superplastic properties have been obtained. .

In the early research work, the rolling plate or extruded plate was used as the starting material of friction stir processing (ActaMaterialia, vol.50, No.17(2002) p.4419-4430), and the process was complicated and the cost was high. In order to simplify the processing procedure, the researchers tried to directly use the cast alloy as the starting material, and directly transformed the coarse cast structure into a fine-grained superplastic structure through friction stir processing, and achieved good superplastic properties (ScriptaMaterialia, vol. 50, No.7 (2004) p.931-935). However, it should be pointed out that due to the obvious composition segregation and microstructure inhomogeneity in alloy castings, not only the processing performance of the alloy is poor, but also it is difficult to achieve complete homogenization of composition and microstructure in one-step friction stir processing.

Invention content:

The purpose of the present invention is to provide a short-flow process fine-grained superplastic material preparation method, which is suitable for processing aluminum alloys, magnesium alloys, zinc alloys, and copper alloys.

The invention provides a method for preparing a short-flow fine-grained superplastic material, which is characterized in that: the as-cast alloy is used as the starting material, and after homogenization heat treatment, friction stir processing is carried out, and the coarse, loose and uneven casting The organization transforms into a uniform, dense fine-grained superplastic structure.

In the method for preparing the short-flow fine-grained superplastic material of the present invention, after the alloy is cast and formed, the friction stir processing is performed after homogenizing heat treatment at a temperature of (0.7-0.85) T _m for 10-24 hours, and the processing tool speed is 400-1500 rpm /min, travel speed 50-400mm/min.

The present invention proposes a new short-flow fine-grained superplastic material preparation method, using as-cast alloy as the starting material, firstly performing homogenization heat treatment to improve the composition segregation and structure inhomogeneity of the casting, and then performing friction stir processing. The coarse casting structure is transformed into a fine-grained superplastic structure, and a new method of casting + homogenization heat treatment + friction stir processing is established. Compared with the rolling (extrusion)+friction stir processing method, the process of the present invention significantly shortens the preparation process of fine-grained superplastic materials and reduces manufacturing costs; compared with the casting+friction stir processing method, the inventive method can prepare A more uniform fine-grained superplastic material significantly improves the superplastic properties of the material. Therefore, there is reason to believe that this new fine-grained superplastic material preparation process will have broad industrial application prospects in the superplastic forming of high-strength alloys.

Detailed ways:

Example 1

Using an 8 mm thick 7075 aluminum alloy as-cast plate, after homogenization annealing at 460 ° C for 24 hours, then friction stir processing, under the processing parameters of tool speed 1200 rpm and travel speed 100 mm / min, the obtained grain Uniform fine-grained structure with a grain size of 3 microns. The superplastic tensile test shows that good superplastic properties are obtained in the temperature range of 350-470°C, and there is no abnormal grain growth at 470°C, and 700% superplasticity can still be obtained. The maximum superplasticity is 1050%, achieved at 450°C and a high strain rate of 1× ^10-2 s ^-1 .

Comparative example 1

Using 8 mm thick 7075 aluminum alloy as-cast plate for direct friction stir processing, under the parameters of tool speed 1200 rpm and travel speed 100 mm/min, a fine-grained structure with an average grain size of 3-5 microns was obtained, but the The particle size and second phase particle distribution are not very uniform. The superplastic tensile test shows that the processed 7075 aluminum alloy obtains superplasticity in the temperature range of 400-450°C, and the superplasticity disappears due to abnormal grain growth due to uneven structure above 450°C. The maximum superplasticity is 600%, achieved at 450°C and a high strain rate of 1× ^10-2 s ^-1 .

Example 2

Using a 6 mm thick 2024 aluminum alloy as-cast plate, perform homogenization annealing at 490°C for 12 hours and then perform friction stir processing. The grain size is obtained under the parameters of tool speed 500 rpm and travel speed 100 mm/min Uniform fine-grained structure of 4.5 microns. The maximum superplasticity achieved is 450%, achieved at 430 °C and a strain rate of 3 × ^10-3 s ^-1 .

Comparative example 2

Using a 6mm thick 2024 aluminum alloy as-cast plate, friction stir processing was carried out under the parameters of the tool speed of 500 rpm and the travel speed of 100 mm/min. After processing, the grain size and the distribution of the second phase particles were not very uniform. The grain size is approximately 5-7 microns. The maximum superplasticity achieved is 300%, achieved at 430 °C and a strain rate of 3 × ^10-3 s ^-1 .

Example 3

Use a 6 mm thick Mg-Zn-Y-Zr as-cast plate, perform homogenization annealing at 420°C for 10 hours, and then perform friction stir processing, under the parameters of tool speed 600 rpm and travel speed 100 mm/min A uniform fine-grained structure with a grain size of 5 microns was obtained. The maximum superplasticity achieved is 550%, achieved at 450 °C and a strain rate of 3 × ^10-3 s ^-1 .

Comparative example 3

Using a 6 mm thick Mg-Zn-Y-Zr as-cast plate, friction stir processing was performed under the parameters of tool speed 600 rpm and travel speed 100 mm/min, the grain size and second phase particle distribution after processing were not Very uniform, with an average grain size of approximately 5-7 microns. The maximum superplasticity achieved is 400%, achieved at 450 °C and a strain rate of 3 × ^10-3 s ^-1 .

Example 4

Using a 5 mm thick Zn-22Al as-cast plate, conduct a homogenization annealing treatment at 200°C for 8 hours and then perform friction stir processing. The grain size is obtained under the parameters of tool speed 500 rpm and travel speed 100 mm/min Uniform fine-grained structure of 3 microns. A superplasticity of 350% was achieved at 160 °C and a strain rate of 1×10 ^-3 s ^-1 .

Comparative example 4

Using a 5 mm thick Zn-22Al as-cast plate, friction stir processing was performed under the parameters of tool speed 500 rpm and travel speed 100 mm/min. After processing, the grain size distribution was not very uniform, and the average grain size was about 3-5 microns. A superplasticity of 240% was achieved at 160 °C and a strain rate of 1×10 ^-3 s ^-1 .

Claims (3)

1. A method for preparing a short-flow fine-grained superplastic material, characterized in that the process is as follows: after the alloy is cast and formed, homogenization heat treatment is carried out to improve component segregation and structural inhomogeneity, and the homogenization heat treatment temperature is (0.7-0.85) T _m , where T _m is the melting temperature of the material in Kelvin, for 10-24 hours; then friction stir processing. 2. According to claim 1, the preparation method of the short-flow fine-grained superplastic material is characterized in that the friction stir processing parameters are as follows: the speed of the processing tool is 400-1500 rpm, and the travel speed is 50-400 mm/min. 3. The short-process fine-grained superplastic material preparation method according to claim 1, characterized in that said alloys include aluminum alloys, magnesium alloys, zinc alloys, and copper alloys.