Effect of Hydrogen on Phase Transformation, Thermal Deformation Behavior, and Forming Limit of TC2 Alloy

Abstract

The present study investigates the effect of hydrogen addition (0-0.44 wt%) on the phase transformation, thermal deformation behavior, and forming limit of TC2 alloy. The α þ β ! β phase transformation point decreases with an increase in the hydrogen content. When the hydrogen content was 0.44%, the α þ β ! β phase transformation point is 720 C, a decrease of more than 200 C compared with the 0H alloy. The optimal hydrogen content is 0.18 wt %, as determined by tensile testing. The ultimate tensile stress of the 0.18H alloy measured at 600 C and a 0.001 s À1 strain rate is 11% lower than that of the 0H alloy, whereas the elongation percentage is 41.5% higher. The results indicate that hydrogen promotes the slip deformation and the dynamic recrystallization of the α phase of the alloy. The forming limit diagrams (FLDs) of the 0H and 0.18H alloys are obtained by bulge testing. The forming limit of the 0.18H alloy is significantly higher than that of the 0H alloy. The FLD 0 value of the 0.18H alloy (0.230) is approximately 16% higher than that of the 0H alloy (0.199), indicating that a 0.18 wt% hydrogen content can effectively improve the plasticity of TC2 alloy.