Numerical modelling and effects of reinforcement addition on the microstructural evolution of additive manufactured ti-6al-4v alloy

Ti-6Al-4V alloy possesses extensive usage and unique properties, but its poor hardness and susceptibility to fail by galling under conditions of sliding contact or fretting and poor tribological behaviour in terms of large and unstable friction coefficient have limited its industrial applications. The microstructure of these alloys is highly influenced by processes involving plastic deformation and thermal treatments which, in effect, determines the mechanical properties adhering to desired properties. Direct laser metal deposition (DLMD) technique can be used to address the limitations associated with titanium alloy. This is mostly achieved by integration of reinforcement materials into the main matrix to form coating. Thereby inducing microstructural changes to the material.The morphology and also the hardness property of the various composite coatings were examined. Strong metallurgical bond without pores and cracks were observed between the coating and the substrate. Grain refinement was observed within the microstructure as the grains grew in a columnar and dendritic pattern in a counter direction to heat flow. Nevertheless, further results revealed that addition of titanium and copper brought transformation to the microstructure of Al-Cu-Ti coatings from a dendritic structure to a flower-like microstructure. Therefore, the coating exhibited a defect free, refined microstructure with significantly improved micro-hardness due to formation of various intermetallics. COMSOL Multiphysics was used to model the temperature distribution within the melt pool.