Nanoindentation and isothermal compression behaviour of Al–4Cu–Ni composites

Abstract

The present investigation explores the nanoindentation and isothermal compression behaviour of Al–4Cu-xNi (x = 2, 4, 6, 8 and 10 wt%) Aluminium matrix composites produced by pressureless sintering technique. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses of sintered samples reveal the presence of core-shell type Al3Ni and Al3Ni2 intermetallic formation at the interface between Ni particulates and the Al–Cu matrix. Nanoindentation study shows hardness of 1.55 ± 0.15, 4.65 ± 0.44, 21.02 ± 0.42, 13.17 ± 0.13, 5.53 ± 0.89, 6.28 ± 0.19, 8.39 ± 0.14 GPa corresponding to α-Al matrix, Ni, Al3Ni2, Ni and Al3Ni2 interface, Al3Ni, and their respective interface. The composite containing 10 wt % Ni possesses the highest yield strength at room temperature. At 200 °C it could retain 54 % of its room temperature strength (91 MPa). The HR-TEM analysis shows that particulate and precipitation hardening was the predominant mechanisms during the initial stage of an isothermal compression. However, as the compression progressed, the pinning effect, dynamic recovery (DRV), and work hardening mechanisms became active. According to the current study findings, interface qualities substantially impact composite performance at both room temperature and elevated temperatures. The creation of strong intermetallic compounds (Al3Ni2 and Al3Ni) due to an intensive endothermic interaction between the Al and Ni particles is linked to this effect.