STUDY OF THE RESIDUAL-STRESS IN COLD-ROLLED 7075-AL-SIC WHISKER-REINFORCED COMPOSITES BY X-RAY AND NEUTRON-DIFFRACTION

Many surface treatment techniques are used to improve the mechanical b ehavior of metal matrix composites (MMC) under dynamic loading. Mill m achining, shot-peening, hammering, and cold-rolling are the four techn iques commonly used. In this paper, we study the effect of the surface treatment with the cold-rolled technique on the residual stresses in an aluminum alloy 7075 reinforced with 27% vol fraction SiC whiskers. The techniques used to measure the residual stresses are X-ray and neu tron diffraction methods. Neutron diffraction is a nondestructive tech nique that allows one to evaluate the residual stresses in both the Al matrix and the SiC whiskers. The X-ray technique was used to evaluate the residual stresses at the surface of the composite material. The r esults show us that the cold-rolled treatment induced a steep stress g radient near the surface. The comparison of using the two different me asuring techniques will be discussed.