Study On Preparation Of Fine Grain Pure Copper By Shear-rolling And Heat Treatment

Performance of metal material and its grain size have close immanent connection. the smaller the grain size is, the higher the mechanical properties of material such as strength, hardness, and plasticity will be. So the grain refinement has drawn wide attention from domestic and foreign material science researchers. So far, it has made great progress in theory and industrial application, and has formed a variety of methods of preparing ultrafine-grained materials, of which the most widely used one is severe plastic deformation, mainly including accumulative equal channel angular pressing, roll-bonding, high pressure torsion and cyclic extrusion-compression. However, due to the small size of the deformation device, it is difficult to realize the scale of production. This paper carried out an exploratory study, for material shear deformation with shear deformation devices of independent research and development, and also studied how deformation at different shear angles will affect the rate of composite average grain size of materials.This paper selected the pure copper strip with thickness of4mm, and purity of99.9%as the sample deformation material. Firstly, it will be reduced in thickness to1.58mm by rolling deformation, then the strip material will get shearing deformation. The main results are as follows:(1) The best heat treatment system of the pure copper strip is340℃×7min. There is a great impact of annealing temperature on the microstructure of pure copper, under the same annealing time, the higher the heat treatment temperature is, the faster grain growth, and the final average grain size increase. If the temperature is higher than340℃, the grain will grow too fast, the final grain size will be coarse. When it is lower than300℃, the grain will grow slowly, the grain morphology and size will not change significantly.(2) The average grain size of pure copper strip will reach minimum after six times of shear-rolling deformation at50°, and the strip sections perpendicular to the rolling direction, the strip sections parallel to the rolling direction, and the strip section parallel to the rolling direction are respectively8.04μm,10.34μm and8.65μm in the minimum average grain size.(3) The average grain size of pure copper strip will reach minimum after nine times of shear-rolling deformation at60°, and the strip sections perpendicular to the rolling direction, the strip sections parallel to the rolling direction, and the strip section parallel to the rolling direction are respectively3.81μm,5.04μm and3.53μm. in the minimum average grain size.(4) The bigger the shear angle is, the faster the magnitude decreasing rate of the grain size will be. The average grain size shows a certain declining rate along with the increase of deformation times, and the rate of size reduction will be lessened with the increase of deformation times. Before the fifth avenue of50°deformation, the magnitude of the dimensional changes obvious, From the beginning of the sixth channel, the size did not change significantly, from the eighth avenue of60°deformation, the size did not change significantly.