Microstructures and mechanical properties of (TiBw+Ti5Si3)/TC11 composites fabricated by hot isostatic pressing and subjected to 2D forging

In this study, microstructures and mechanical properties of (TiBw+Ti5Si3)/TC11 composites fabricated by hot isostatic pressing and 2D forging were investigated. A α + β titanium alloy TC11 (Ti-6.4Al-3.5Mo-1.4Zr-0.25Si) was used as a matrix material. The TiB2 addition corresponding to 5.0 and 3.5 vol% of TiBw and the Si addition corresponding to 2.0, 4.0 and 6.0 vol% of Ti5Si3 were used as additives to the TC11 titanium alloy. TiBw and Ti5Si3 reinforced TC11 titanium matrix composites were fabricated by hot isostatic pressing and 2D forging in the α + β temperature field at T = 980 °C. The microstructure of the as-forged composites was composed of nanoscale Ti5Si3 particle within the β-phase and TiBw around TC11 matrix particle. The TiBw reinforcer tend to be distributed along the stretching deformation direction. Compared with the TC11 matrix alloy, the strength of the (2Ti5Si3 +5TiBw)/TC11 composite after 2D forging at room temperature increased by about 90 MPa due to the fine-grain strengthening of the α-phase, the precipitation strengthening of the nanoscale Ti5Si3 silicide, and the load transfer efficiency of TiBw. The main failure mechanism of the composites at room temperature is fracture of TiBw followed by ductile failure of the matrix. (2Ti5Si3 +5TiBw)/TC11 is thought as the optimal choice for engineering application, which UTS and El. at 600 °C are 851 MPa and 11%, respectively, and corresponding values of parameters at 750 °C are 385 MPa and 21%, respectively. Compared to the maximum service temperature 500 °C of TC11 alloy, the service temperature of (2Ti5Si3 +5TiBw)/TC11 composite can be improved by over 100 °C while retaining the similar tensile strength and elongation.