In situ Al 2O 3 particle-reinforced Al and Cu matrix composites synthesized by displacement reactions

Abstract

An innovative in situ reaction technique is developed for the synthesis of Al 2O 3/Al and Al 2O 3/Cu composites. This technique provides a new approach overcoming the problems of loss and agglomeration of reinforcement particles when the particles are added directly into their matrixes by a conventional ex situ technique. The experimental results have shown that the presence of network Al(Cu)–CuAl 2 eutectic, which is detrimental not only to the fracture toughness, but also to the stability of the microstructure, can be reduced from the final product by introducing two or more oxides into the synthesis. Moreover, the network CuAl 2 phase can be eliminated entirely only by changing Al matrix into Cu matrix when Al amount is not excess in the Al–CuO preforms. The mechanisms of formation or absence of Al(Cu)–CuAl 2 eutectic in the Al 2O 3/Al and Al 2O 3/Cu composites are explained based upon thermodynamics of the systems. The modification of the microstructures in the in situ synthesis Al 2O 3/Al, Al 2O 3/Al–Si–Cu, Al 2O 3/Al–Si–Cu–Mn and Al 2O 3/Cu composites can be understood in the light of thermodynamics.