Determination of Thermally and Mechanically Induced Internal Stresses in Metal-Matrix Composites by X-Ray Methods

Abstract

AbstractIn this study the progression of thermally and mechanically induced internal strains (stresses) in metal-matrix composites was investigated by X-ray methods. The materials studied were whisker-reinforced 2124 Al-SiC(w) and 6061 Al- SiC(w) composites. X-ray diffractometry was used to measure thermally induced stresses on samples cycled from ambient to 280°C. Significant variations in residual stress values were observed in the matrix depending on the location and direction of the measurements with respect to the whisker orientation. The determined stress states of the as-processed and the thermally cycled samples were evaluated with continuum models. The microstrains in composites induced during processing and tensile loading were also investigated by nondestructive means. Individual grains of the matrix were analyzed by rocking-curve measurements using a modified X-ray doublecrystal diffractometer. The relationship between the plastic deformation induced by applied loads and the progression of the microstrain/excess-dislocation values was determined.