ANALYSIS OF THERMAL RESIDUAL-STRESSES IN UNIDIRECTIONALLY ALIGNED SICW AL-ALLOY MATRIX COMPOSITES BY X-RAY-DIFFRACTION/

In aluminum alloy matrix composites reinforced with unidirectionally a ligned SiC whisker, thermal residual stresses should be induced anisot ropically in the composite due to the difference in the coefficients o f thermal expansion between the matrix and whisker during quenching fr om high temperatures. The magnitude of thermal residual stresses in th e matrix and whisker in various heat treated composites was investigat ed by X-ray diffraction method at triaxial stress states. Principal st ress components (sigma(11), sigma(22), sigma(33)) induced in the water -quenched composites are high tensile stress stales in the matrix and compressive in the SIC whisker. On the other hand, the shear residual stresses to (sigma(12),sigma(23),sigma(31)) are almost zero. The tensi le residual stress of the whisker axial direction (sigma(11)) in the c omposites is the largest value, and it agrees well with the tensile yi eld strength of the extrusion direction in the water-quenched SiCw/Al alloy composites. The tensile residual stresses of the composites rest ored at room temperature after cooling the water-quenched composites d own to the liquid nitrogen temperature decrease remarkably compared to those of the water-quenched composites.