Densification behaviour and the effect of heat treatment on microstructure, and mechanical properties of sintered nickel-based alloys

The present work focused on the densification behaviour and heat treatment effect on the mechanical properties of spark plasma sintered Ni–Fe–Al–Cr alloys. Five initial alloys were prepared by mixing of elemental compositions of each alloy followed by sintering. The five alloys, Ni–30Fe–20Cr, Ni–30Fe–15Cr–5Al, Ni–30Fe–10Cr–10Al, Ni–30Fe–5Cr–15Al, and Ni–30Fe–20Al, were sintered at sintering temperature of 950 °C, pressure of 50 MPa, heating rate of 150 °C/min, and at a holding time of 10 min and heat-treated. Microstructure and mechanical properties of the sintered alloys were investigated prior to and after heat treatment by scanning electron microscopy (SEM) and a Future-tech Vickers microhardness tester respectively. Results showed that the relative density of the alloys increases as the aluminium content increases. The microhardness increases at 800 °C for 2 h ageing time and decreases after prolonged ageing. Therefore, optimum strengthening of sintered nickel alloys can be obtainable within short duration of ageing as prolonged results in adverse hardness values.