X-ray diffraction analysis of aluminium containing Al8Fe2Si processed by equal channel angular pressing

A 99.1% aluminium with initial grain size of similar to 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 Al8Fe2Si 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 Halder-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 degrees C due to the precipitates which delay the diffusion process. The annealing of the ECA pressed samples up to 400 degrees 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. (c) 2006 Elsevier B.V. All rights reserved.