1971 Volume 35 Issue 2 Pages 97-102
The effect of Zr addition (0∼40 wt%) on the stability of a metastable beta titanium alloy, Ti-15 wt%Mo, was investigated. The measurement of the mechanical properties in various annealing conditions revealed that the stability of Ti-15Mo-Zr alloy changed abruptly at about 5%Zr.
When the alloys containing less than 5%Zr were slow-cooled from the beta region, hardening and embrittlement due to the decomposition of beta was remarkable, and when quenched, a low yield/tensile strength ratio was shown because of martensitic strain transformation.
On the other hand, the mechanical properties of the alloys containing more than 5%Zr did not depend on the rate of cooling from the beta region, and the alloys were stable mechanically and thermally. The TTT diagram obtained by an automatic transformation apparatus and the changes in the mechanical properties during aging showed that Zr in a meta-stable beta alloy, Ti-15Mo, suppresses and retards the omega precipitation. The beta stabilizing power of Zr which was calculated from the slope of β⁄α+β solvus in the Ti-Zr equiliblrium diagram was weak, but the above-mentioned beta stabilizing effect of Zr in the Ti-15Mo alloy was as strong as that of Mo.