High oxygen-content titanium and titanium alloys made from powder

摘要

Oxygen remains to be a central issue in the manufacture of titanium (Ti) and its alloys from powder. The strong and short-range repulsion between interstitial oxygen and screw dislocation core strengthens titanium but compromises its resistance to cracking. It is therefore challenging to produce strong and ductile (tensile) Ti materials from high oxygen-content powder. This article reviews the tensile properties of high oxygen-content alpha-Ti, (alpha+beta)-Ti alloys, and beta-Ti alloys made from powder. A minimum tensile ductility value of 6% is used to define ductile Ti according to existing technical specifications for Ti-6Al-4V and other powder metallurgy materials. Two post-processing methods, solution heat treatment and thermomechanical processing, are identified to be effective remedies to convert non-ductile high oxygen-content Ti alloys into ductile ones. The underlying ductility-improvement mechanisms are discussed, which vary with alloy system. In particular, redistribution of oxygen between alpha and beta phases by solution heat treatment offers a practical remedy to substantially improve tensile ductility, e.g., from 6% to 19% for the Ti-0.94 wt%O alloy. It is shown that appropriate post processing can enable a wide variety of Ti alloys made from powder to tolerate >= 0.5 wt%O for >= 6% tensile ductility for structural applications. (c) 2020 Elsevier B.V. All rights reserved.