The research focuses on the fatigue and fracture toughness of Ti-6Al-4V manufactured by Selective Laser Melting (slm) of fine powder. This manufacturing approach offers remarkable design flexibility as layers can be built up at approximately 50-100 micron layer increments. Consequently very complex shapes can be achieved and minimal machining is required. For very complex parts selective laser melting may be a viable alternative to conventional casting, forging and machining. The process does, however, result in significant residual stresses as well as significant surface roughness and some minor porosity, all of which can impair mechanical properties. The fatigue and fracture toughness behaviour of suchslmTi-6Al-4V alloys fabricated by laser melting can depend substantially on the interlayer bonding, as this method could lead to lines of weakness between melted layers or even very poorly melted and bonded layers. This project then endeavours to measure the fatigue behaviour in the form of a fracture mechanics based “Paris equation” and fracture toughness of selective laser melted material in two orientations, namely the fatigue crack grown (i) perpendicular and (ii) parallel to build direction. Such fatigue data would be invaluable in the assessment of fatigue lives of components made of such material.

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This work explores the fatigue life implications of porosity, microstructure, and the presence of residual stresses of laser powder bed fusion (LPBF)–produced Ti6Al4V. In particular, this study considers stress vs cycles to failure and its link to porosity levels, the underlying microstructure, and the presence of residual stresses. It is shown that both porosity and microstructure play the significant role that adversely affect fatigue life. However, neither play a leading role, and the combination of the two that govern the fatigue life performance of LPBF‐produced Ti6Al4V. Residual stresses are shown to have a lesser influence.

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