2006 年 70 巻 7 号 p. 579-585
Effect of oxygen on phase stability and elastic deformation behavior after cold working of Ti-Nb-Ta-Zr-O alloys were investigated by employing tensile test, microstructure observations, in-situ XRD analysis, and electrical resistivity measurements. The specimens were Ti-36%Nb-2%Ta-3%Zr-0.35%O (mass%) alloy (Gum Metal) and the reference alloys having lower and higher oxygen contents (from 0.07% to 0.93%) than that in Gum Metal. Pseudo-elastic deformation with rearrangements of α″ variants was observed in the specimen with 0.07% oxygen content. As the oxygen content was increased, the generation of α″ was suppressed and yield strength was increased. The elastic behavior in Gum Metal with 0.35% oxygen content showed non-linearity, with the slope of the stress-strain curve in the elastic region continuously decreasing with stress increase. In-situ XRD measurements during tensile loading in Gum Metal showed that all β peaks shift monotonically to higher 2θ angles with increasing tensile strain up to 2.7%. This result indicates that elastic behavior in Gum metal is not accompanied by phase transformation, such as stress-induced α″. The higher oxygen content alloy with 0.93% had linear elastic deformation behavior and a yield strength of about 1600 MPa. Additionally, the starting temperature of athermal ω formation was lowered with increasing oxygen and cold working.