日本金属学会誌

J. Japan Inst. Metals, Vol. 70, No. 7 (2006),
pp. 579-585

Effect of Oxygen on Phase Stability and Elastic Deformation Behavior in Gum Metal

Tadahiko Furuta1, Shigeru Kuramoto1, Chen Rong1, Junghwang Hwang1, Kazuaki Nishino1, Takashi Saito1 and Masahiko Ikeda2

1Toyota Central R&D Labs., Inc., Nagakute, Aichi 480-1192
2Department of Materials Science and Engineering Faculty of Engineering, KANSAI University, Suita 564-8680

Abstract:

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.


(Received 2006/3/17)

Keywords:

beta-titanium, titanium-niobium-tantalum-zirconium-oxygen, phase-stability, non-linear elasticity, effect of oxygen, electrical resistivity


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