Effect of HIP on mechanical property of additively manufactured Ti6Al4V alloy

Abstract

Direct Metal Laser Sintering (DMLS)0is a highly versatile and efficient Powder Bed- Fusion (PBF) additive manufacturing (AM) technique that is widely utilized in various industries such as aerospace, automobile, and biomedical. The present study investigates the effect of Hot Isostatic Pressing on mechanical property of DMLS produced Ti6Al4V alloy. Experimental studies have showed that the HIP reduces anisotropic and porosity, produces homogeneity in material. In the present study HIP was done at three different temperatures 700°C, 910°C and 1060°C. The microscopic analysis shows that the as built and HIPed samples have different microstructures. Further the x-ray computed tomography, commonly used to display the pores in a given volume, shows the effect of HIP in reducing porosity. Apart from porosity HIP process also eliminates the sub-surface defects of DMSL produced Ti6Al4V alloy samples. It was observed that HIP was unable to eliminate all the defects, however, significant reduction of defects size was observed for all the cases. It was also observed that there is a direct relation between decrease in pore size and fatigue performance of DMLS produced Ti6Al4V alloy. As the defect size and shape controls the fatigue performance of DMLS Ti6Al4V, it was found that a pore with a size of ˃40μm can initiate the fatigue crack. Based on these, it can be concluded that the reduction in defect size will definitely decrease the number of crack initiation point, which will further improves the mechanical properties of DMLS produced Ti6Al4V alloy.