The Effect of Constant and Variable Temperatures on Fatigue Behavior of Ti6Al4V-ELI Alloy Produced by Laser Powder Bed Fusion Additive Manufacturing

The increasing use of additively manufactured Ti6Al4V components in engineering highlights the necessity of understanding their thermo-mechanical behavior under service conditions. This study systematically investigates the fatigue response of L-PBF-produced Ti6Al4V-ELI alloy under various thermal environments, including constant (25 degrees C, 50 degrees C, 250 degrees C) and cyclic (-50/+50 degrees C) conditions. The influence of heat treatment below the beta-transus temperature and electrochemical polishing on fatigue performance was assessed via stress-life tests. Microstructural and mechanical characterizations were performed through XRD, SEM, EDX, microscopy, and Vickers hardness testing. Results revealed that elevated and cyclic temperatures significantly reduce fatigue life, whereas postprocessing treatments notably enhance fatigue resistance. The lower fatigue limit increased from 260 MPa (as-built) to 500 MPa (heat-treated), and the upper limit from 400-410 MPa to 700-710 MPa. Microstructural analysis identified strain accumulation and microporosity near fracture surfaces, offering insights into the degradation mechanisms under thermal fatigue loading.