Roles of reinforcements in twin nucleation and nano-α precipitation in the hybrid TiB/TiC-reinforced titanium matrix composites during high-temperature fatigue

Abstract

Almost no studies have been carried out on the roles of reinforcements in the microstructural evolution of the titanium matrix composites (TMCs) during high-temperature fatigue. In this paper, short TiB fibers and TiC particles enhanced the dislocation accumulation in the primary α and β phases, and we found a new phenomenon in which {101¯2} deformation twins nucleated at two interfaces: the α/β interface and the reinforcement/matrix interface. Dislocations can decompose into twinning dislocations due to the local stress concentration and result in twin nucleation. Moreover, under thermal activation, dislocations act as channels for rapid diffusion of elements (V, Al and O), resulting in numerous nano-α phases precipitating in the β phase, increasing the local stress concentration at primary α/β interface, which was conducive to twin nucleation. Our work helps further clarify the roles of reinforcements and to supplement the mechanism underlying TMC fracture during high-temperature fatigue.