Improvement in the mechanical properties of wire arc additively manufactured Ti6Al4V through grain refinement and process stabilization

In this study, an attempt has been made to attain better microstructural characteristics and mechanical properties of wire arc additively manufactured Ti6Al4V. In order to achieve so, the effect of input process parameters on process stability and part integrity has been analyzed. A detailed experimental investigation on tensile and compression behavior, impact toughness, and microhardness has been attempted without any post-processing technique. It has been found that individual and combined effects of bridged material transfer and controlled heat intensity influence in reducing the defects and enhancement of the material’s properties. The microstructural analysis of as-deposited Ti6Al4V confirmed the formation of fine acicular α laths due to the solid-state β→α phase transformation due to higher solidification rate. The grain refinement is found to result in enhanced grain boundary length, decreased effective slip length, and α colony size. Moreover, tensile test results confirmed the fulfillment of minimum strength and ductility requirement specified by ASTM F1108 and ASTM F136. Furthermore, compressive yield strength and maximum % strain are found to be 22.97 and 36.74% higher than its as-forged counterpart. Similarly, as-built part is found to absorb more impact energy than wrought Ti6Al4V by providing higher resistance to crack propagation under impact load. Therefore, grain refinement through process stabilization can result in improved mechanical properties and may be considered as an alternative to post-treatment techniques for additively manufactured parts.