Effect of heat treatment on the variable amplitude fatigue life and microstructure of the novel bioinspired Ti‐6Al‐4V thin tubes fabricated using Selective Laser Melting process

Abstract In this study, thin tubes are mimicked based on the architecture of Euplectella aspergillum and studied for fatigue performance under variable amplitude loading. The thin tubes are fabricated with Ti‐6Al‐4V material using the selective laser melting (SLM) process. SLM printed components are always subjected to residual stresses, which can reduce fatigue performance of the components. Heat treatment effect on the fatigue performance, microstructure, and residual stress is studied. Complex geometry and sharp corners in the bioinspired tubes result in stress concentration, which further reduces the fatigue performance. The value of residual stresses at the sharp corners is dependent on the height of the tube, thickness of struts, and intersection of different struts. Heat treatment significantly reduces the residual stresses and increases the fatigue life of the thin tubes; however, strength decreases after heat treatment. Heat‐treated thin tubes showed a higher concentration of (α + β) phase, which results in decreased residual stress and improved ductility of the thin tubes. Advanced bionic thin tubes can be used for lightweight crash boxes, sandwich panels, bio‐implants, grid stiffened structures, etc.