A study on defect-induced fatigue failures in SLM Ti6Al4V Alloy

Abstract

Additive Manufacturing has been developed to fulfill the current growing demand for design freedom structures with near-net complex shapes. The additive manufacturing process is associated with lots of defects such as porosities, incomplete fusion, hot cracking, delamination, etc. These defects act as stress raiser and are known to deteriorate the mechanical properties of the alloy. In this present study, the defect-based fatigue performance of selective laser melted Ti6Al4V alloy has been investigated. The Ti6Al4V alloy specimens were vertically built with optimized process parameters and layer thickness of 60 µm. These as-built specimens were subjected to heat treatment in order to reduce the residual stress generated due to higher thermal gradient. The as-built alloy mainly consisting of α’ martensitic microstructure decomposes into α-β microstructure with the heat treatment. The mechanical properties and fatigue performance were then evaluated. Most of the fatigue failure occurred from the surface and sub-surface regions. The endurance limit then predicted using the defects’-based model using the defects’ area and its location.