Analysis of Fracture Toughness and Crack Propagation of Ti6Al4V Produced by Selective Laser Melting

This paper describes and analyzes fracture toughness and crack propagation of selective laser molten (SLM) components made from Ti6Al4V powder particles. The main goal of this research is to gain more insight in the fracture mechanisms of this relatively new material and to improve the static and dynamic behavior of cracked SLM-Ti components. At first, the SLM process parameters are optimized until the relative material density equals 99.7%. This is close to the relative density of vacuum arc remelted mill annealed standard oxygen titanium which is used as a reference for all experiments. A distinctive difference in phase morphology and texture of the microstructure is noticed between the SLM and the reference titanium. The fine acicular martensite phase of the SLM-Ti results in more brittle behavior and inferior fracture toughness. On the other hand, the fine grained microstructure leads to a large number of grain boundaries acting as obstacle points for crack propagation. Consequently, crack growth properties do not significantly differ between both. Microstructural analysis of the crack growth and final failure areas on the fractured surfaces is performed to study the failure mechanisms in more detail.