HOT FORMABILITY OF AN A12009 20SIC(W) COMPOSITE SHEET/

Although high-strain-rate superplasticity of metal-matrix composites ( MMCs) has attracted much research attention in the last decade, most r esearchers still use uni-axial tensile tests to investigate the formab ility of MMCs. In this paper, a new fully-computer-controlled superpla stic bulge tester has been developed to study the hot formability of a n aluminum-matrix composite sheet under complex stress states. Thin 20 vol.% SiC whisker-reinforced 2009 aluminum sheets (2009Al/20SiC(w)) w ith thicknesses of 2.0 and 2.3 mm were bulged at a constant polar stra in-rate of 2.0 x 10(-1) s(-1) and at a optimum temperature of 808 K in elliptical dies with aspect ratios of 1:1, 4:3, 2:1. 8:3 and 4:1. The forming-limit diagram of the MMC was determined for the first time. I t was shown that the forming limits increases with increasing sheet th ickness, and that the general shape of the curve is different from tha t of conventional forming-limit curves. (C) 1998 Elsevier Science S.A.