AL-SIC INTERFACE STRUCTURE STUDIED BY HREM

A comparison is made between the two well-known aluminium alloys 2014 and 6061, cold pressed from powder and subsequently extruded, with and without a reinforcement of 30 wt% alpha-SiC particulates. The former one has a strength of 550 MPa and a strain at fracture of 1% while the latter one has a more moderate strength of 415 MPa but a fracture strain of 4%. A high resolution electron microscopy study of the Al SiC interface indicates that proper wetting is achieved in both alloys. A preferred orientation relationship is observed in the 6061 SiC combination: (0001)SiC//{111}Al; [2110BARBAR]SiC//[110]Al. When the (0001)SiC is not parallel to the interface, a stepped interface is observed with the 6061 alloy, with one part of the step parallel to the SiC basal plane and one type of the Al octahedral planes and the other part parallel to another type of Al octahedral planes. In the 2014 alloy the steps seem to be less pronounced probably due the processing route.