Positive effect of hydrogen on interface of in situ synthesized Ti-6Al-4V matrix composites

Abstract

This paper presented another methodology, melt hydrogenation (melting alloys in gas mixture of argon and hydrogen), to produce in situ synthesized Ti-6Al-4V matrix composites (TMCs) with quality interface after hot deformation. Microstructure results of as cast TMCs indicated hydrogen didn’t obviously change morphology of interface, but induced more TiBw whiskers with higher length-diameter ratio, which was attributed to hydrogen improving growth rate of TiBw whiskers by accelerating atomic diffusion. After hot compression, experimental results indicated proper content of hydrogen addition decreased the flowing stress of both matrix and TMCs, and eliminated most cracks and holes along the interface, quality interface without defects was attributed to improvement on flowing ability of matrix alloy. The positive effect of hydrogen on interface was explained by hydrogen induced softening on matrix alloy. Electron back-scatter diffraction (EBSD) images indicated hydrogen increased softer β phase content which was favor to fill up the defects caused by crush of ceramic particles. And hydrogen promoted discontinuous dynamic recrystallization (DRX) by accelerating migration of grain boundaries which ended up at the interface, and then eliminated defects caused by disharmonious motion between ceramic particles and matrix.