Study on high cycle fatigue performance at elevated temperature for a selective laser melted Ti6Al4V alloy

Abstract

Abstract Selective laser melted Ti6Al4V alloy has broad application prospects in aeroengine field. In this study, high cycle fatigue tests were carried out systematically using hourglass shaped specimen (K t=1) at 400 °C. The S-N curves were acquired and compared with data of the casting and the forging. The anisotropy and the defect effects of the fatigue performance were analysed. The LOF defects on the surface and subsurface preferentially act as the fatigue crack initiation site for almost all the tested HCF specimens. The position and irregularity of defect have greater influence on elevated temperature fatigue life than the defect size. The fatigue strength of horizontal orientation is lower than that of vertical orientation, because of the characteristics of larger size, more irregular shape and higher density for the crack source defects of horizontal specimens. The fatigue performance of the SLM Ti6Al4V alloy in this study is better than that of the casting and even the forging, but the dispersion of fatigue data of the SLM alloy is much greater than that of the both traditional process alloys.