Mechanical properties of SiC particle–AZ31B magnesium alloy machined chips composites prepared by hot extrusion after ECAP

Abstract

Wear resistance and mechanical properties of hot extruded AZ31B/SiC particle composite, where the hot extrusion billets were processed by ECAP, were investigated. Uniform dispersion of SiC particles was observed after extrusion for the mean particle size of 1.2∼11 μm constituting 0 to 6% volume fraction of SiC particle content, where the particles had been thinly adhered to the surface of the machined chips of ECAP-hot extrusion samples before extrusion. However, when the SiC particle size is under 3 μm, the aggregates at the triple junction of the interfaces of the machined chips could not be decomposed and dispersed. To solve this problem, hot extrusion was carried out using various cold green compacts prepared by repetitive ECAP processed up to 7 times. As a result, refinement of grain size was obtained for the ECAP extruded materials by decomposition and dispersion of the SiC particles with increase in the ECAP frequency. Consequently, it was possible to obtain the composite of AZ31 magnesium base alloy machined chip and SiC particle which contains almost uniformly dispersed SiC particles. Furthermore, the average grain diameter of the matrix was very much refined to approximately 2 μm, and σB, σ0.2 were also improved. Frictional wear test shows that abrasion resistance was further improved for N=7 extruded materials than N=4 samples due to more homogeneous mixing of the SiC particles as well as decomposition and dispersion of the aggregates.