Experimental realisation of build orientation effects on the mechanical properties of truly as-built Ti-6Al-4V SLM parts

Studying the mechanical properties of Selective Laser Melting (SLM) fabricated titanium parts built in a horizontal direction, parallel to the substrate, in a truly as-built condition, has always been a challenge. The problem is mainly related to the stress relaxation of horizontal parts after removal from the substrate, which causes a noticeable level of distortion when compared with vertically printed parts with no observable distortion. In this study, a novel design has been developed that enables fabrication of straight undistorted horizontal parts via an SLM route with no post-processing steps, and thus the mechanical properties of horizontal Ti-6Al-4 V (Ti64) samples in their truly as-built condition have been reported and compared with their vertically built counterparts. The study reveals that the vertical samples suffer from premature fracture in their truly as-built condition, while the horizontal parts perform similarly to post-treated samples. The analysis of the tensile test results shows that the fracture stress (maximum stress) of the truly as-built vertical parts is below the yield stress (YS) of the horizontal parts in their truly as-built condition, i.e. nearly 38 % of the Ultimate Tensile Strength (UTS). In addition to the truly as-built condition, the effect of machining was also studied to further highlight the effect of as-built surface removal on the mechanical properties of both vertically and horizontally deposited Ti-6Al-4 V(Ti64) SLM parts.