Interface Stability in Diffusion Couple of L 10 type TiAl and L 12 type ( Al , Mn ) 3 Ti Alloys at 1273 – 1473 K ∗ 1

Titanium trialuminide coating on L10-type titanium aluminide alloys represents a valuable mean to improve oxidation resistance. Selection of L12-type titanium trialuminide alloys containing Mn as a coating material is particularly attractive because of its good ductility at room temperature and good oxidation resistance at high temperature of 1273 K. However, stability of the coated titanium trialuminide at high temperature and adhesion to the substrate are not established. Two kinds of diffusion couples composed of L10 and L12 single phase alloys with or without vanadium were applied to diffusion experiments in a temperature range of 1273–1473 K for 2.5–20 h. During the diffusion process, L10 and L12 phases coexisted without any inter-phase, irrespective of diffusion temperature and vanadium addition. The diffusion couples composed of the alloys without vanadium exhibited cracked region at the interface between the L10 and L12 phases, while the diffusion couples composed of the alloys with vanadium exhibited no cracked region. The L12-type alloy with vanadium was shown to be an appropriate coating material on the L10 alloy.