Effects of Multi-Directional Forging on the Microstructure and Mechanical Properties of an AZ80/SiC Nanocomposite

AZ80-1.5 Vol.% SiC nanocomposite was produced by the stir-casting method. The cast specimens were annealed and subjected to multi-directional forging (MDF) for up to 8 passes at 250 °C. Shear punch test (SPT), Vickers microhardness test, and uniaxial tension test were employed to evaluate the mechanical properties of nanocomposite before and after MDF process. Microstructural studies showed that the average grain structure was refined and the grain size distribution became more uniform after all MDF passes. The most pronounced grain refinement was obtained after eighth passes of MDF, where the average grain size of the unprocessed material was reduced from 31.4 to 4.9 µm. Based on the results of shear punch test (SPT), both shear yield stress (SYS) and ultimate shear strength (USS) of the nanocomposite were significantly improved after eight passes of the MDF process. The values of SYS and USS in the unprocessed specimen were 123.7 and 158.9 MPa, respectively, which increased to 164.6 and 194.1 MPa after eight MDF passes. Processing by MDF resulted in the enhancement of microhardness, strength, and ductility of the nanocomposite. After 8 MDF passes, improvements of 22.4, 48.1, 45.2, and 8.5% were obtained for the microhardness, TYS, USS, and elongation, respectively. The mechanisms of these improvements were discussed based on the microstructural features of the material.