The effect of different build orientations on the consolidation, tensile and fracture toughness properties of direct metal laser sintering Ti-6Al-4V

Abstract

Purpose The purpose of this paper is to study new process parameters which were selected to achieve the full density of Ti-6Al-4V samples in different building orientations and investigate fracture toughness property and its relation to the microstructure, an area which has not previously been reported in full detail and which may offer information to a designer. Direct metal laser sintering (DMLS) is an additive manufacturing technique that directly manufactures three-dimensional parts, layer-by-layer, to scan and melt metal powders for aerospace applications. Design/methodology/approach Hardness and tensile tests were carried out to evaluate the effect of consolidation on the mechanical performance of specimens made at three different building directions. Optical and electron microscopy were used to characterise the microstructure of the DMLS specimens and their effects on the fractures and mechanical properties. Findings It was found that the built samples have an excellent density at 4.5 g/cm, and the sample surfaces parallel to the building direction are rougher than the perpendicular surfaces. The fracture toughness result was higher than that of the cast material for the same alloy and higher than the Ti-6Al-4V parts fabricated by electron beam melting. This results in the superior mechanical properties of DMLS, while slightly lower in the zy direction owing to cracks, porosity and surface finish. Research limitations/implications The tensile strength was found to be higher than the wrought material, and the samples exhibited brittle fractures owing to the martensitic phase, which is caused by a high temperature gradient, and the mechanical properties change with the change in the microstructures at different building directions. Originality/value This paper contains original research.