Influence of particulate size on creep properties of TiB-reinforced orthorhombic Ti-22Al-27Nb

Abstract

Intermetallic titanium alloys based on the orthorhombic phase Ti2-Al-Nb exhibit a higher ductility and fracture toughness compared to other intermetallic systems such as TiAl and super-2 (Ti3Al) [1]. These are under development for applications up to 700°C in aeronautic gasturbines. The reinforcement with titanium boride (TiB) particulates leads to an improvement of the mechanical properties. TiB is chemically and physically compatible with titanium alloys, especially with respect on the coefficient of thermal expansion. The effect of the reinforcement is influenced not only by the volume content but also by the size of particulates. Subject of this study are the creep properties of Ti-22Al-27Nb alloy reinforced with 6.5% TiB. It has been reported recently, that smaller particulates enhances the tensile strength as well as the fatigue strength [2]. Reasons for the additional reinforcing effects can be found in the micromechanisms of plastic deformation such as blocking of dislocations.