Microstructure evolution and tensile behavior of MgAlB4w/Al composites at high temperatures

Abstract Aiming at developing high temperature resistance aluminum matrix composites for both structural and functional purposes, the novel MgAlB4 whisker reinforced Al matrix composites with directional distributed reinforcement were fabricated using powder metallurgy followed by hot extrusion. The microstructure characterization demonstrated that Al grains exhibited a distinct Al texture and MgAlB4 whiskers aligned along the extrusion direction in the as-extruded composites. The high temperature tests indicate that UTS of the 20 wt% MgAlB4w/Al composite at 200 °C and 300 °C can reach up to 266 MPa and 166 MPa, respectively, with a CTE of 23.7 × 10−6 K−1 at 300 °C. The whiskers distributed within the grains have a pinning effect on the dislocation movement and the whiskers distributed on the grain boundaries impede the grain boundaries sliding and migration. Additionally, the failure behavior changes from MgAlB4 whiskers fracture to interfacial debonding of MgAlB4w-Al matrix as the temperature increases.