Densification, microstructure and properties of mechanically alloyed and hot-pressed Cu–15 wt% Al alloy

Abstract

In the present work, hot press of Cu–15 wt% Al alloys was carried out in a vacuum environment at a sintering temperature of 500 °C for 30 min with varying pressure (100–500 MPa) to densify the alloys. Both the density and hardness of Cu alloys were significantly increased with increasing the hot press pressure. A maximum density of ~ 94.5% ρth (theoretical density) and microhardness of ~ 6.2 GPa was achieved for Cu–Al alloy after hot press at 500 °C with 500 MPa pressure application. The XRD, SEM-EDS analysis confirms the presence of solid solution α (Cu0.78Al0.22) and γ (Cu9Al4) inermetallic phases in the sintered samples. Maximum hardness of 7.88 GPa and elastic modulus of 177.35 GPa was measured for Cu–Al alloy using nano-indentation test. It must be noted that so far in the literature a maximum hardness of 4.9 GPa was reported for Cu-based materials. The alloy was also measured with a moderately high compressive yield strength (1019 MPa), compressive strength (1106 MPa), and a reasonable amount of strain (6.6%). The wear tests revealed that the Cu–15 Al alloy hot pressed at 500 MPa pressure can exhibit better wear properties. Low coefficient of friction (COF) of 0.15 and wear rate of 0.71 × 10−5 mm3/N-m was observed at a sliding speed of 0.25 m/s and high COF of 0.20 and wear rate of 4.33 × 10−5 mm3/N-m were noted with further increasing the sliding speed (1.25 m/s). Further microstructural characterization of worn surfaces reveals abrasion wear as the major dominant wear mechanism. The present work clearly demonstrates the use of a high amount of hot press pressure in achieving good sinter density for Cu–15 wt% Al alloys with superior hardness, better wear and compressive strength properties.