Plastic deformation-induced improved mechanical and thermal properties in hot-forged SiC-TiC composite

Abstract

A novel SiC-20 vol% TiC composite prepared via a two-step sintering technique using 6.5 vol% Y2O3-Sc2O3-MgO exhibited high deformation (60 %) on hot forging attributed to the high-temperature plasticity of TiC (ductile to brittle transition temperature ∼800 °C) and fine-grained microstructure (∼276 nm). The newly developed SiC-TiC composite exhibited a ∼2-fold increase in nominal strain as compared to that of monolithic SiC. The plastic deformation caused by grain-boundary sliding in monolithic SiC was supplemented by the plastic deformation of TiC in the SiC-TiC composite. The hot-forged composite exhibited anisotropy in its microstructure and mechanical and thermal properties due to the preferred alignment of α-SiC platelets formed in situ. The relative density, flexural strength, fracture toughness, and thermal conductivity of the composite increased from 98.4 %, 608 MPa, 5.1 MPa‧m1/2, and 34.6 Wm−1 K−1 in the as-sintered specimen to 99.9 %, 718–777 MPa, 6.9–7.8 MPa‧m1/2, and 54.8–74.7 Wm−1 K−1, respectively, on hot forging.