Influence of Al4C3 nanophase on structural stability and mechanical properties of Al-Al4C3 composites after thermal exposure

摘要

The Al-Al4C3 metal matrix composite (MMC) reinforced by Al4C3 nanoparticles was produced by a powder metallurgy route. Well-dispersed coherent Al4C3 phase was formed during the fabrication process, which guarantees good interface bonding and thus results in good mechanical properties. Yield strength (YS) for materials strengthened by 1 wt.% of C reached 275 MPa, ultimate tensile strength (UTS) 295 MPa and elongation (A) 14%, which means that this material can compete with Al matrix strengthened by comparable amount of carbon nanotubes (CNTs/Al). To analyse the thermal stability, the Al-Al4C3 composite was exposed to a temperature of 250 degrees C, 500 degrees C and 620 degrees C for 5 hours with subsequent gradual furnace cooling to room temperature. The composite exhibits high structural stability (the subgrains size after thermal treatment at 250 degrees C was similar to 0.82 mu m and did not change to a temperature of 500 degrees C) with preserved mechanical properties up to 500 degrees C. After thermal exposing to 620 degrees C, the subgrains size increased, by almost twice the initial value (similar to 1.93 mu m) and degradation of substructure was observed, but the material maintained good YS (similar to 220 MPa) and UTS (similar to 245 MPa) values. The structural and mechanical properties of the composite, even after thermal treatment, are significantly determined by the Al4C3 phase created "in situ". Thus, we suggest that Al-Al4C3 composites might be a good alternative, depending on the application purpose, to CNTs/Al composites.