Evaluation on Tensile and Fatigue Crack Growth Performances of Ti6Al4V Alloy Produced by Selective Laser Melting

Additive manufacturing (AM) technologies are increasing in importance for aerospace application, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. As the most widely used and studied alloy for this technology, Selective laser melting (SLM) produced Ti6Al4V alloy is evaluated on tensile and fatigue crack growth (FCG) performances at RT and 400℃. Conventionally manufactured Ti6Al4V alloys are concerned for comparison. Different orientations are considered to investigate the anisotropy of tensile and FCG behavior. The results show that, the tensile properties at RT and 400℃ are highly dependent on the specimen orientation relative to build direction. The FCG resistance is related to specimen orientation in the near threshold region but no relationship with specimen orientation in the steady growth stage at RT. The FCG resistance is much less influenced by specimen orientation at 400℃. The tensile strength at RT and 400℃ of SLM alloy reaches even exceeds the strength level of conventionally manufactured alloys such as forging, bar and casting. The steady stage FCG resistance under stress ratio of 0.1 of SLM alloy is also comparable to conventionally manufactured alloys. The SLM alloy shows higher FCG resistance under stress ratio of 0.1 than 0.5, but the da/dN-△K curves of the two stress ratios are very close to each other. The steady stage FCG rate at RT is slower than 400℃ in the lower △K region and faster in the higher △K region.