Quenching and thermal cycling effects in a 1060-Al matrix-10vol.%Al₂O₃ particulate reinforced metal matrix composite

In this study, the effects of quenching and thermal cycling on a 1060-Al matrix-10vol.%Al₂O₃ particulate reinforced composite were investigated. A rapid increase in the flow stress with increasing quenching temperature was found to result from solution hardening of the matrix due to solutionizing of reaction products and impurities. The matrix chemistry plays an important role in the strengthening of commercially pure Al matrix composites, although the effect of impurities or alloying elements is usuaally considered to be insignificant in commercially pure aluminum. The cooling rate was found to have no significant influence on the density of dislocations generated by the mismatch in thermal expansion coefficient. Dislocations were observed to be more homogeneously distributed near interface regions compared with matrix regions well away from particles. The dislocations punched out from the interface are thought to be distributed rather randomly so as to screen the thermal residual stress developed by the mismatch in thermal expansion coefficient. Thermal cycling of the composite was found to promote the formation of more stable dislocation tangles and cells.