焼入れTi-V合金の電気比抵抗と組織に及ぼす酸素量の影響

Abstract

Specific resistivity values of Ti-V alloys previously measured by the present authors were slightly different from those reported by Ho and Collings. Such difference may be attributed to different impurity content, especially oxygen, in the samples. The present study was undertaken to elucidate an effect of addition of oxygen on the specific resistivity and the hardness for three series of the alloys, Ti-10 to 40%V, Ti-20%V and Ti-30%V quenched from temperatures of β phase range. Phase constitution at the RT was confirmed by X-ray diffraction.The following results were obtained:(1) X-ray phase constitution of Ti-V-0.3%O alloys showed no remarkable difference from previous alloy series containing about 0.1%O. Lower end of V content range showing nagative temperature dependence were lowered by addition of 0.3%O than previous alloy containing 0.1%O. Oxygen addition always increased the ρ values.(2) Excepting 15%V, oxygen addition increased hardness. In 20%V alloys, hardening was smaller than other alloys, suggesting that an athermal ω volume fraction existing at RT was decreased by the oxygen addition.(3) In the Ti-20%V-Y%O alloys containing more than 0.2%O, ρLN/ρRT became larger than unity, and temperature of ρ maximum on ρ-T curve was lowered with increasing oxygen content.(4) The oxygen addition to Ti-30%V alloy showed a less drastic influence on ρ-T curve than the case of Ti-20%V alloy. Temperature coefficient of resistivity decreased with oxygen content, and a minimum of ρ appeared at 240 K by addition of 1.05%O.(5) These observations indicate that starting and finishing temperatures of the athermal ω formation are lowered with increasing oxygen content.The difference in measured resistivity values reported by individual investigators may be explained by the difference in oxygen content.