Study of transformation behavior in a Ti-4.4 Ta-1.9 Nb alloy

An alloy of composition Ti-4.4 wt.% Ta-1.9 wt.% Nb is being developed as a structural material for corrosion applications, as titanium and its alloys possess excellent corrosion resistance in many oxidizing media. The primary physical metallurgy database for the Ti-4.4 wt.% Ta-1.9 wt.% Nb alloy is being presented for the first time. Determination of the beta transus, M-s temperature and classification of the alloy have been carried out, employing a variety of microscopy techniques, X-ray diffraction (XRD), micro-hardness and differential scanning calorimetry (DSC). The beta transition temperature or beta transus determined using different experimental techniques was found to agree very well with evaluations based on empirical calculations. Based on chemistry and observed room temperature microstructure, the alloy has been classified as an alpha + beta titanium alloy. The high temperature beta transforms to either alpha' or alpha + beta by a martensitic or Widmanstatten transformation. The mechanisms of transformation of beta under different conditions and characteristics of different types of a have been studied and discussed in this paper. (C) 2004 Published by Elsevier B.V.