1990 Volume 40 Issue 12 Pages 885-890
Aluminum matrix composites preforms containing silicon carbide whiskers (SiCw) were fabricated by reactive low pressure plasma spraying, to form aluminum nitrides (AlN) in the plasma flame. SiCw distribution was nearly uniform in the sprayed preform. The alignment of SiCw in the preform was improved from 3-dimensional to planar random by hot-forging at 873K with 196MPa. However, the average length of SiCw, which was 15μm as recieved, was shortened to 6μm through the processing. Reactive low pressure plasma spraying gave a formation of approximately 2vol% AlN, as a secondary reinforcement, with chamber pressure of 13.3kPa. The hot-forged hybrid MMCs showed higher tensile strengths compared to those without AlN. Aluminum powder size affected the SiCw distribution in the sprayed preform, and also finer matrix powder was of advantage to forming more AlN and strengthening the MMCs. Reactive low pressure plasma spraying with nitrogen and hydrogen mixed plasma gas contributed to more AlN formation due to higher plasma flame temperature. Such an improved processing for strengthening can be applied to aluminum alloy matrix composites.
