Microstructure and Mechanical Properties of Bimodal Heterogeneous Tibw/Tc4 Composites with High Strength and Toughness

Abstract

Heterostructure has been improved to improve the comprehensive performance of materials. In this work, bimodal heterogeneous TiBw/TC4 composites with fine-grained TC4 (FG) as the main matrix plus different contents of uniformly distributed coarse-grained TC4 (CG) zone were successfully prepared by two-step low-energy ball milling and vacuum hot-pressing sintering (HPS). TiBw is dispersed in the FG zone and distributed in a near-circular shape at the CG boundaries. At the same time, compared with homogeneous composite (TMC0), the introduction of CG can also refine matrix grains, which is beneficial to the improvement of comprehensive mechanical properties. The optimized heterogeneous TMC has a 10 wt.% of CG, whoes tensile strength is 1129.5 ± 8.2 MPa and elongation is 4.3 ± 0.3%. Compared with TC4 matrix, it has increased by 17.2% and 38.7%, respectively. Compared with TMC0, the average tensile strength did not decrease while the elongation increased by 377.8%. The fracture toughness is 37.9 ± 1.7 MPa·[[EQUATION]], which is 67.0% higher than that of TMC0. Back stress strengthening, plastic deformation in the CG zone, and failure of TiBw are the key in delaying the cracking of heterogeneous TMCs and improve the mechanical properties.

Keywords: Titanium matrix composites, powder metallurgy, Heterogeneous structure, Strengthening and toughening