STUDY ON THE RELATIONSHIP BETWEEN THERMAL EXPANSION BEHAVIOR AND INTERNAL STRESSES OF AN SiC WHISKER REINFORCED COMPOSITE

This paper deals with the relationship between thermal expansion behaviors and internal stresses of SiC_W/Al composites quenched from 600℃ by water and annealed from 600℃ with a cooling rate of 1℃/min. The results show that the dislocation density, residual tensile stress in the matrix and yield strength of the quenched composite are larger than those of the annealed composite. There are two peaks on the curve of the coefficients of thermal expansion (CTE) vs heating temperature of the quenched composite. The first peak appears at about 80℃, and the second one appears at 245℃, and the latter is much higher than the former. But only one peak appears at 80℃ on the curve of the CTEs vs temperature of the annealed composite, and the peak is smaller than the first one of the quenched specimen. The CTE of the annealed specimen increases with temperature increasing gradually. The first peak on the curve of CTE vs temperature is the result of relaxation of the residual tensile stress in the matrix, while the second one is a signal of the relaxation rate of the compressive stress in the matrix of the composite.