Influence of Al4C3nanophase on structural stability and mechanical properties of Al-Al4C3composites after thermal exposure

Abstract

The Al-Al4C3metal matrix composite (MMC) reinforced by Al4C3nanoparticles was produced by a powder metallurgy route. Well-dispersed coherent Al4C3phase 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-Al4C3composite was exposed to a temperature of 250 °C, 500 °C and 620 °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 °C was ∼0.82 μm and did not change to a temperature of 500 °C) with preserved mechanical properties up to 500 °C. After thermal exposing to 620 °C, the subgrains size increased, by almost twice the initial value (∼1.93 μm) and degradation of substructure was observed, but the material maintained good YS (∼220 MPa) and UTS (∼245 MPa) values. The structural and mechanical properties of the composite, even after thermal treatment, are significantly determined by the Al4C3phase created “in situ”. Thus, we suggest that Al-Al4C3composites might be a good alternative, depending on the application purpose, to CNTs/Al composites.