Superplasticity in an aluminum alloy 6061/Al(2)O(3)p composite

The superplasticity of an Al(2)O(3)p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special therm omechanical processing or hot rolling, simple hot extrusion has been employ ed to obtain a fine grained structure before superplastic testing. Superpla stic tensile tests were performed at strain rates ranging from 10(-2) to 10 (-4) s(-1) and at temperatures from 833 to 893 K. A maximum elongation of 2 00% was achieved at a temperature of 853 K and an initial strain rate of 1. 67x10(-3) s(-1). The highest value obtained for the strain rate sensitivity index (m) was 0.32. Differential scanning calorimeter was used to ascertai n the possibility of any partial melting in the vicinity of optimum superpl astic temperature. These results suggested that no liquid phase existed whe re maximum elongation was achieved and deformation took place entirely in t he solid state.