AA7075/HEA composites fabricated by microwave sintering: Assessment of the microstructural features and response surface optimization

Abstract

Aluminium 7075 (AA7075) is a desirable grade of aluminium alloy highly sought after for its high strength-to-weight ratio. In this study, AA7075/Fe1.2CrZnCuAlTi0.8 (HEA) composites were prepared by microwave sintering, and a response surface methodology (RSM) was employed in the experimental design and analysis of the results. The variable input factors for a constant dwell time of 20 min are HEA dosage (5 wt%, 10 wt%, and 15 wt%), compaction pressure (20 MPa, 60 MPa, and 100 MPa), and sintering temperature (300 °C, 450 °C, and 600 °C). The properties examined were tensile strength, elastic modulus, elongation, microhardness, flexural strength, and impact strength. The outcome showed that 5 wt%, 10 wt%, and 15 wt% played an important role in the microstructural evolution of the composites for all temperature ranges. The XRD analysis detects the presence of α-aluminium, BCC phase, MgZn2, Al7Cu2Fe, and Al9Co2 phases as the sintering temperature increases. ANOVA results indicated that the input factors and their interactions played a major role in the responses. The surface plots revealed that 5 wt% – 10 wt% HEA reinforcement and 300 °C–450 °C sintering temperature improved the responses, whereas 10 wt% – 15% and 450 °C–600 °C were detrimental to the properties of the sintered composites. 20 MPa–100 MPa displayed favourable contribution on all response parameters. From the analysis, the optimum input combinations for achieving the desired strength enhancement in Fe1.2NiCrCoAlTi0.8 particles (HEAp) reinforced AA7075 alloy are 11.7% HEA, 75.2 MPa pressure, and 447.7 °C sintering temperature.