Influence of channel angle on the development of ultrafine grains in equal-channel angular pressing

Equal-channel angular pressing provides a convenient procedure for introducing an ultrafine grain size into a material. Using samples of pure Al, rests were conducted to determine the influence of the channel angle phi, defined as the angle of intersection of the two channels within the die, on the subsequent microstructure attained by pressing. Experiments were performed using dies having channel angles from 90 to 157.5 degrees. The results show that an ultrafine microstructure of essentially equiaxed grains, separated by high angle grain boundaries, is achieved only when a very intense plastic strain is imposed on the sample in each passage through the die as when using a die having a channel angle of phi close to 90 degrees (C) 1998 Acta Metallurgica Inc.