Impression creep behavior of extruded Mg-SiCp composites

Impression creep experiments were performed on pure magnesium and its composites reinforced with 5, 7.5, 10 and 15 vol% of 10-μm SiCp fabricated by powder metallurgy and extrusion processes. Tests were conducted on planes perpendicular to the extrusion direction, in the temperature range 423-473 K and under stress level in the range 150-250 MPa. Analysis of data showed that for all loads and temperatures magnesium reinforced with 10 vol% SiCp had the lowest creep rates, and thus, the highest creep resistance among all materials tested. The improved properties of the composite materials were discussed based on various strengthening mechanisms. The stress exponents of 7.0-7.9 and activation energies of about 90 kJ mol-1, which are close to that for dislocation-pipe diffusion in Mg, were almost the same for all tested materials. These creep parameters imply that the dominant creep mechanism could be dislocation climb controlled by pipe diffusion.