Aligned TiB whiskers in TiB/Ti6Al4V composites manipulated by spark plasma sintering and hot extrusion: In-situ rotation and strengthening mechanism

Abstract

In this work, 3.5 vol% TiB/Ti6Al4V composites with aligned TiB whiskers are synthesized by spark plasma sintering-hot extrusion (SPSHE). The effects of deformation temperature and deformation amount on the microstructure evolution and tensile properties are systematically investigated in composites. The results suggest that the dispersion of TiB whiskers is gradually improved with the deformation increasing from 30%, 50%–70%. TiB whiskers obtain a highly consistent orientation as the composite is deformed by 70%. The multiplication of more dislocations induced by TiB whiskers provides the driving force for dynamic recovery and dynamic recrystallization of the composite during SPSHE. In addition, the matrix microstructure of the composite is composed of α phase, β phase and interface L phase. The interface L phase decreases the mean free path of dislocation slip and improves the strength of the composite manipulated by SPSHE. The tensile strength (1294 ± 20 MPa) and elongation (5.0% ± 0.5%) of the composite with a deformation amount of 70% at 950 °C are well combined. According to the analysis results of the microstructure and fracture, the strengthening mechanism of the composite is the TiB load transfer strengthening effect and the matrix strengthening effects including interface L phase strengthening, fine grain strengthening, substructure strengthening and texture strengthening.