X-ray diffraction analysis of aluminium containing Al_8Fe_2Si processed by equal channel angular pressing

摘要

A 99.1 percent aluminium with initial grain size of approx 85 mu m was deformed by equal channel angular (ECA) pressing. The sample undergoes an effective strain of 1.07 N by N passes through the die. The material contains a low volume fraction of Al_8Fe_2Si precipitates located essentially at the grain boundaries. The analysis of the X-ray diffraction peaks showed a significant broadening, which was related to grain refinement and lattice distortions. The crystallite size, calculated using the Haider-Wagner method, reached 225 nm after two passes and did not subsequently change. A decrease of the lattice parameter was also observed after ECA pressing. This is due to a partial dissolution of the precipitates. The microstructure was stable up an annealing of 200 deg C due to the precipitates which delay the diffusion process. The annealing of the ECA pressed samples up to 400 deg C leads to a decrease in the X-ray diffraction peaks broadening and an increase of the lattice parameter. This is due to grain growth.