Microstructure and mechanical properties of a spray deposited SiCp/Al composite processed by hot extrusion and equal channel angular pressing

An ultrahigh strength silicon carbide particle reinforced aluminium matrix composite (SiCp/Al), in which the volume of SiC particles was similar to 15% and the initial size was similar to 10 mu m, was prepared using a spray deposition technique, and then hot extrusion and equal channel angular pressing (ECAP) were performed on the composite to investigate the evolution of microstructures and mechanical properties. Microstructural observations revealed that homogeneous equiaxed grains were obtained and the grain size was reduced from similar to 3.0 mm to similar to 400 nm after four passes of ECAP using route B-c. SiC particles were broken from similar to 10 to similar to 2 mu m sized fragments by the huge shear stress, and many cavities between the broken SiC particles developed; these cavities derived from the broken SiC particles were filled with the Almatrix. Following T6 heat treatment (comprising solution heat treatment and then artificial aging), the microstructure of the equal channel angular pressed SiCp/Al composite showed a very high stability; the tensile strength, yield strength, modulus and elongation of the composite were 770.0 MPa, 575.0 MPa, 106.6 GPa and 7.4% respectively.