THERMAL CYCLING PROCESSES IN METAL-MATRIX COMPOSITES

Aluminium-matrix composites have attracted considerable academic and i ndustrial attention in recent years, where modulus increases of 100% a nd strength increases of 60% over conventional metal alloys have been reported, Further, the emphasis on the use of recyclable and environme ntally-friendly materials has lent support to the aluminium industries vis-a-vis other materials. The high specific strength and modulus mak es this class of materials highly desirable for the aerospace and tran sport industries. Aluminium-matrix composites are, however, inherently brittle, thus making superplastic forming an alternate and attractive option. In this work, a study of the behaviour of AA6061 reinforced w ith alumina particles produced by casting and extrusion, under the act ion of strain control and thermal cycling conditions, is presented. Co mparisons are made with unreinforced AA6061 matrix, and also with the same composite re-extruded to obtain finer grain sizes. Elongations ob tained via thermal cycling are compared with those from room temperatu re and isothermal testing. The work also looks at the differences in c ycling at different frequencies, range and rate, for the AA6061 matrix composites. (C) 1997 Published by Elsevier Science S.A.