Structure and mechanical properties of Ti-6Al based alloys with Mo addition

In the present study, the effect of molybdenum (Mo) on the structure and mechanical properties of Ti-6Al based alloys have been investigated. The experimental results indicate that these alloys obviously have different structures and mechanical properties with the addition of various amounts of Mo content. The Ti-6Al is composed of hexagonal α phase and α2 phase and exhibits a feather-like morphology. When 1 wt% Mo is introduced, the structure remains essentially unchanged. However, with 3 or 5 wt% Mo addition, several metastable β phase starts to appear and the alloys are dominated by hexagonal α phase, α2 phase and β phase. The binary Ti-6Al alloy has lower yield strength, tensile strength, elongation and reduction of area than all the alloys containing Mo. Ti-6Al-5Mo and Ti-6Al-3Mo alloys exhibit excellent strength and ductile properties due to the retention of metastable β phase with increasing Mo content, and the lowest Young's modulus is found in Ti-6Al-3Mo alloy. On the other hand, Ti-6Al-3Mo alloy displays a characteristic dimple-like ductile fracture with a large number of tear ridges on the fractured surfaces, but Ti-6Al-5Mo alloy features more transgranular cleavage cracking in conjunction with some dimples. This study concludes that Mo not only enhances the hardness of titanium alloy, but also improves its plasticity, the Ti-6Al-3Mo alloy has a great potential to use as a dental machining alloy.