Optimization of process parameters for the development of Ni–Al-Ti-Mn-Co-Fe–Cr high entropy alloy system via spark plasma sintering

Abstract

A novel equal atomic Ni–Al-Ti-Mn-Co-Fe–Cr high entropy alloy (HEA) was developed via the spark plasma sintering (SPS) process. This study investigates the influence of the sintering parametric processes, which consist of the sintering temperature (ST) and heating rate (HR) at constant pressure and dwelling time (DT) on the Microhardness (MH) and relative density (RD) of the developed HEA. Response surface methodology (RSM) was used to develop a predictive model. The design of experiment (DOE) approach was adopted to reduce the number of experiments and eliminate trial by error. ST and HR were considered model variables in developing the model. The user-defined design (UDD) under RSM was used to predict the optimal sintering parameters, and an experiment was conducted to validate the result. The result indicates that ST and HR play a significant role in achieving high densification and hardness. The developed alloy shows the highest MH value of 136.3 HV at 850 °C and an HR of 100 °C/min. Equally, the least crystallite size of 2.05 µm was realized at the maximum ST. However, the modeling response suggested that full densification of about 99% can be achieved at an ST of 850 °C, a pressure of 50 MPa, a DT of 5 min, and an HR of 100 °C/min.