Microband formation in cyclic extrusion compression of aluminum

The influence of very large deformations on the properties and microstructu res of Al99.95 and Al99.992 is investigated. The very large deformations ar e imposed by the cyclic extrusion-compression (CEC) method, which combines extrusion and compression processes. It is found that above true strains of 4 and 8 respectively, the compression proof stresses of Al99.992 and Al99. 95 stabilize. The property stabilization appears to result from the increas ing incidence of microbands which leads to the final constancy of the micro structure parameters. The homogeneous chess-board like microstructure forms during the deformation by the CEC method, as the result of rearrangement o f microstructure by the mutually crossing microbands leading to the final d ominance of persistent macro shear bands. (C) 1998 Canadian Institute of Mi ning and Metallurgy. Published by Elsevier Science Ltd. All rights reserved .