| 摘要 |
PURPOSE:To attain grain refining in a base phase and to allow superplasticity capable of providing large deformation with minimal stress to appear by finely precipitating alpha-phase at a temp. not higher than isothermal working temp. before applying isothermal working to a preworked beta titanium alloy. CONSTITUTION:Preworking is applied at >= about 70% draft to a beta titanium alloy at a temp. in the temp. region where working is relatively easy and an alpha-phase is hardly precipitated and then to precipitation treatment at a temp. in the (alpha+beta) two-phase region between about 400 deg.C and the beta-transformation point, by which the alpha-phase is precipitated finely and uniformly. Then, isothermal working is exerted at a temp. not lower than the precipitation temp. and between about 650 deg.C and the beta-transformation point, by which superior superplasticity can be allowed to appear in the beta titanium alloy. By this method, total elongation can be improved as compared with the conventional hot working and isothermal working. As a result, the variety of design can be provided while making the most of transfer characteristics and diffusion joining property. |
