Effect of hydrogen on microstructure evolution and tensile properties of TC21 alloy

Hydrogen can be used as a temporary element to refine microstructure and improve workability of titanium alloys. In this article, the influence of hydrogen on the microstructure evolution and tensile properties of TC21 alloy is investigated. The microstructure observation reveals that the FCC hydrides δ precipitate firstly at the grainboundaries of primary α phases in TC21 alloy with hydrogen contents above 0·319 wt-%. These hydrides which block the grains deformation reduce both the strength and ductility at room temperature. With increasing hydrogen contents, the elevated temperature strength decreases first and then increases, while the ductility behaves the contrary. These are resulted from the interaction of hydrogen induced softening and hardening.