Effects of heat treatment on the thermal expansion behavior of SiC whisker reinforced aluminum composite

The thermal expansion behaviors of commercially-available SiC whisker reinforced pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors were greatly affected by heat treatment. To explain the results, the microstructures and thermal mismatch stresses in the matrix of the composite were examined by the transmission electron microscope and X-ray diffraction, respectively. The results show that the dislocation density and thermal mismatch stresses in the matrix of the composites water-quenched from 600°C are much higher than those of the composite slowly cooled from 600°C. The analysis suggests that the coefficients of thermal expansion (CTE) are closely related to the change of thermal mismatch stresses and the yield strength of the matrix of the composite. The comparison of the coefficients of thermal expansion between experiments and calculations suggests that the temperature behaviors of CTE of SiC/Al composite agree better with those of Kerner's model within lower temperature range.