Correlations among microstructure, crystallographic texture and mechanical properties of AA7475-T7/SiC/Al2O3 surface composite fabricated via FSP

Abstract

In this study, AA7475-T7/SiC/Al₂O₃ hybrid surface composites (HSCs) were fabricated via friction stir processing (FSP) by using different rotational speeds of 900 rpm, 1100 rpm and 1300 rpm, and different reinforcement combinations of SiC and Al₂O₃ by vol%. These composites are recognized as S1 (900 rpm, 7 % SiC and 13 % Al₂O₃), S2 (1100 rpm, 13 % SiC and 7 % Al₂O₃) and S3 (1300 rpm 10 % SiC and 10 % Al₂O₃). Composite (S3) emerged as the best composite, achieving the highest ultimate tensile strength (UTS) of 656 ± 5.81 MPa, a highest microhardness of 281 ± 2.93 Hv with a minimum residual stress of −80 ± 5.0 MPa as supported by tensile test, Vickers hardness test and Chromium X-ray tube test respectively. The microscopic observations revealed that S3 consisted of highly refined grains with an average grain size (AGS) of 3.17 ± 0.09 µm, a high fraction (90.20 %) of the high-angle grain boundaries along with B and C major shear texture components as evident by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) analyses. Overall, the study demonstrates the strategy of selection of FSP rotational speed and reinforcement combination to develop the desired mechanical properties in AA7475-T7 based hybrid composite.