A new approach to correlate the defect population with the fatigue life of selective laser melted Ti-6Al-4V alloy

By Y. Hu, Sheng-chuan Wu, Z. Wu, X. Zhong, S. Ahmed, S. Karabal, Xianghui Xiao, Huilan Zhang, P. J. Withers. 2020

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Abstract Microstructural features and defects arising from selective laser melting (SLM) determine the in-service performance of additively manufactured near-net-shape components. Here the grain type, shape, size and distribution were characterized using electron backscattered diffraction (EBSD). High-resolution synchrotron radiation X-ray computed tomography (CT) was used to quantify the population, morphology and dimensions of porosity and lack of fusion defects. For SLM Ti-6Al-4V alloy, the larger-sized defects in comparison with the α grains are more important for crack initiation, typically leading to poor fatigue resistance and a pronounced variation in fatigue life. The fatigue strength was then evaluated in terms of the defect population using a combination of the statistics of extremes and the Murakami model. Finally, an extended Kitagawa-Takahashi fatigue diagram was established within the framework of defect-tolerant design, which includes a classical safe-life region and the defect-determined lifetime in the finite life region.

Subfields: Automotive Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/0067c9ee35e0d185167b9b0075dcb4e68c73d7f7