Microstructural and nanoindentation study of spark plasma sintered high entropy alloy reinforced aluminium matrix composites

In this study, Spark Plasma Sintering (SPS) also known as a field-assisted technique was employed in the fabrication of high entropy alloy (HEA) reinforced aluminium matrix composites (using 5, 7 and 10 wt% HEA as the reinforcement in the composites); and conventional methods were employed to determine the relative density and microhardness; while nanoindentation technique was employed to determine the nanohardness, modulus of elasticity and nanoindentation depth of the sintered samples. Calculation Phase Diagram (CALPHAD) software, Thermocalc was employed in the prediction of the phases present in the HEA, while XRD was used in the confirmation of the phases. The phase analysis showed that BCC, FCC, and laves are the phases present in the fabricated HEA while the microstructural analysis showed that interdiffusion layers were formed; and atomic precipitation that resulted in the formation of new phases occurred during sintering. The microhardness, nanohardness, and modulus of elasticity of the sintered HEA-reinforced Al matrix composites increase with an increase in the wt% of HEA such that as little as 5 wt% HEA addition resulted in a 102.8 % increment in microhardness, while the densification and indentation depth were discovered to decrease with an increase in the wt% of HEA."