On the Influence of Microstructure on the Fracture Behavior of Gamma-Based Titanium Aluminides. III. Effects of Interstitials and Microalloying with W

Abstract

The results of a recent study of the effects of interstitial elements and microalloying with 11.2 at.% W on the tensile and fracture properties of Ti-48AI (compositions quoted in atomic % unless stated otherwise) base gamma alloys are presented in this paper. Lower interstitial oxygen levels are shown to promote higher levels of tensile ductility at the expense of yieldlultimate tensile strength and fracture toughness. Microalloying with W is also shown to result in microstructural instability and a concomitant degradation in tensile and fracture properties. Ductility and yieldlultimate tensile strengths in binary gamma alloys at room-and elevilled-te~nperature are shown to exhibit a simple Hall-Petch dependence on the average grainllamellar packet size. The observed Hall-Petch behavior is found t c~ be independent of lamellar volume fraction and fracture mechanism at room.. and elevated-temperature. The implications of the results are discussed for fut~~re alloylprocess development.