The Effect of Porosity, Oxygen and Phase Morphology on the Mechanical Properties of Selective Laser Melted Ti-6Al-4V with Respect to Annealing Temperature

In the present study, Ti-6Al-4V alloy was fabricated by Selective Laser Manufacturing (SLM) technique and subsequently subjected to an annealing treatment at, above and below the β transition temperature. We emphasized the influence of porosity, oxygen and phase morphology on the strength, ductility and elongation of SLM-manufactured Ti-6Al-4V and compared the alloy's properties with conventionally manufactured Ti-6Al-4V from the literature. The as-built Ti-6Al-4V sample showed a very high strength due to acicular martensite, and the growth of α+β lamellae on heat treatment improved ductility. Energy Dispersive Spectroscopy (EDS), Optical and Scanning Electron Microscopy (SEM) were used to identify the chemical composition, calculate lamellar width and analyze the fracture mechanisms. The grain size and the average thickness of α lamellae, inter-granular β and prior β grain boundary increased with annealing temperature. The porosity and oxygen content of the samples were found to have a consequential effect on the strength, especially in as-built and high-temperature annealing conditions and optimum mechanical properties were observed in SLM Ti-6Al-4V annealed at 800 °C.