Effect of cyclic heat treatment on the microstructures and mechanical properties of Ti–Si alloys

Abstract

Abstract Samples of Ti-8Si, Ti-13.67Si and Ti-23Si (at.%) alloys treated using different cyclic heat treatment processes have been investigated using X-ray diffraction, optical microscopy and scanning electron microscopy. The microstructures, Vickers hardnesses and compressive properties of the as-cast and annealed samples are compared. For the Ti-8Si and Ti-23Si alloys, only the eutectic microstructure in the as-cast alloy is obviously altered after annealed at 900 °C (where β-Ti is stable) for 20 min and then cooled in air with six cyclic treatments, or firstly treated at 900 °C (where β-Ti is stable) for 20 min followed by quenching in air, and then treated at 700 °C (where α-Ti is stable) for 40 min followed by cooling in furnace, with six cycles) cyclic heat treatment. The microstructure of Ti-13.67Si alloy changes from the features of clubbed and larger sized Ti5Si3 grains to finer grain size during different cyclic heat treatment. Vickers hardness of all alloys is significantly increased in the cyclic processing. For the Ti-23Si alloys, particles in the eutectic structure of as-cast alloy were spheroidized after cyclic heat treatment, resulting in increasing of both Vickers hardness and compressive properties.