Roll Preparation Of Ultrafine Grained Copper Process On The Basis Of Research

Moderate refinement of grain is an effective method to enhance service and shaping properties. ARB(accumulative roll-bonding) is one of the most promising industrial techniques that can refine conventional grain size to submicrometer or nanometer level. Recently, it has become the hotspot of research. Systemic research was investigated about ARB of pure Cu in this paper, including the comparison of ARB and asynchronous-ARB roll ing , the effects of all kinds of technical factors on the microstructures and properties of matial-such as true strain, anneal temperature and time.Systemic study has been doae by three different experiments. Micros--tructures was observed and physical properties was test in each exper-iment. Firstly the fact -which the lower anneal temperature is and the more true strain is, the thinner crystalline grain is - was founded from the result of ARB experiment by SEM observation, EBSD analyses and micro hardness test. Secondly, based on last experiment asynchronous-ARB exper-iment had been done with some parameters of technics changed as following: lowering anneals temperature in lower passes and rising anneal tempera -ture with shortening anneal time in higher passes. The results of samples treated by asynchronous-ARB technics revealed that σ_b δ% and micro hardness had been enhanced notably, but at the same time σ₀.2 and σ₀.2/ σ_b are as low as normal pure Cu untreated. Finally nonanneal continual ARB experiment had been done to verify whether" lower σ₀.2 σ₀.2/σ_b was affected by anneal or not. Results of this experiment are exiting that all physical properties are much higher than those treated by conventional technics. And Critical Accumulate deformation amount was considered to appear at third pass, where physical properties of samples reached Maximum and could not increase even HpformRtion continuing.Experiment conclusion revealed thai ARB and asynchronous-ARB can thincrystalline grain and improve properties of material in effect; Processing after critical accumulate deformation amount can not improve properties of material but reduce them; Anneal in middle passes can strongly affect o02, o 02/a h of samples. It can be inferred from result of experiment that the mechanism of "strengthen by crystalline grain thinning* be only valid within the specific limits, after the crystalline grain is thinning to certain extent, it be unable to make the intensity of material improved even continue processing. We discussed it with the view that "crystalline grain distortion can be saturated *.