Effect of N on microstructure and mechanical properties of as-cast Ti-6Al alloy

In-situ titanium matrix composites with N content of 0.045-0.27 wt% have been produced by a casting method. The microstructure and mechanical properties of as-cast materials have been observed and tested. The results show that when N content in Ti-6Al alloy is between 0.045 wt% and 0.27 wt%, the reinforcement is a compound of Ti, Al and N, and volume fraction of reinforcements increases with an increase of N content. The hardness, compressive strength and elastic modulus are all higher than that of the matrix alloy. With the increase of N content, the compressive strength, the hardness and the elastic modulus increase. Fracture surface analysis has also shown that the matrix alloy fractures in a ductile model and the composites fracture in a cleavage brittle model with characteristics of dimple and cleavage surface.