Mechanical Properties of Ti-Mn-Al-Fe Alloys after Solution Heat Treatment

Abstract

To develop a low-cost β Ti alloy, the influence of Mn in Ti-Al-Fe alloys on solution treatment behavior and mechanical properties was investigated. Although it has been known that Mn is a β stabilizing element in Ti alloys, Mn has not often been used for Ti alloys in spite of its low cost and sustainability so far, since Mn easily evaporates under low-pressure atmosphere, which is a common condition when melting Ti alloys. Therefore, general β Ti alloys include a high amount of expensive elements such as V, Mo and Nb to stabilize the β matrix phase. In this paper, Ti-8 to 10Mn-1Fe-3Al alloys (mass%) were produced by cold crucible levitation melting under atmospheric pressure to inhibit Mn loss by vaporization. As results, it was found that the β transus was lowered with increasing Mn amount, but the full β phase was obtained in solution-treated alloys over 1113 K, even in the 8%Mn alloy. Through tensile and Charpy impact tests of the full beta-phase samples, the ductility and toughness increase monotonically with increasing Mn amount from 8 to 10% in spite of the tensile strength having almost constant value. Ti-10Mn-1Fe-3Al alloy has the best mechanical properties among the alloys used in this study.