超塑性加工に適した Ti 合金の設計

概要

論文の詳細を見る
Using four kinds of α+β titanium alloys (Ti-Al-V-Sn-Zr-Mo-Cr-Fe system), the effects of test temperature and volume fraction of α phase on superplastic properties were investigated. (1) Total elongation of each alloy was more than 400% in the temperature range between 1023K and 1123K at the strain rate of 6.7×10^<-4>s^<-1>. Maximum flow stress increased with decreasing temperature rapidly in the temperature range lower than 1073K. From these results, the temperature range between 1073K and 1123K was considered to be suitable for superplastic forming of these alloys at the strain rate of 6.7×10^<-4>s^<-1>. (2) The effects of test temperature and volume fraction of α phase on the strain rate sensitivity, m, were examined by multiple regression analysis. Following regression equation was obtained. m=-17.128(〓-1.095)^2-0.514(V_α-0.426)^2+0.422 〓 : Test temperature K×10^<-3>, V_α : Volume fraction of α phase From this equation, titanium alloys whose volume fraction of α phase is 0.426 at the temperature of 1095K are considered to give the maximum m value and the best superplastic properties at a strain rate of 6.7×10^<-4>s^<-1>. (3) α phase was formed at the surface of specimen due to the reaction with oxygen during high temperature tensile test in an argon atmosphere. Such α phase was expected to be detrimental for superplastic forming and to reduce ductility of the material.
1988-01-01