Abstract
The Ti6Al4V is a cold dwell sensitive alloy, as evident from the failure investigations of several aerospace fan discs and past laboratory research data. However, the studies on the dwell-fatigue sensitivity of additively manufactured Ti6Al4V alloy and its underlying failure mechanism at room temperature are limited. In this study, the cyclic plasticity behavior and the cold dwell sensitivity of powder-bed fusion based additively manufactured Ti6Al4V alloy has been investigated. The standard test specimens of Ti-alloy were fabricated using the selective laser melting process and were subjected to the low cycle fatigue and low cycle dwell fatigue tests, at the same strain rate. A significant reduction in the fatigue lives of specimens exposed to a dwell period was observed at relatively lower strain amplitudes, while fatigue lives were nearly the same at higher ones. The fractographic analysis of the broken specimens revealed multiple crack initiation regions under the action of dwell loadings. The cracks were initiated either from the process-induced defects or by the mechanism of facet formation in the α laths. The failure mechanism based on stress redistribution and its relaxation are discussed to explain the observed results and are presented in this study.
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