Influence of Heat-treatment on Microstructure and Mechanical Properties of Ti-6Al-4V ELI Plate

摘要

Ti-6A1-4V ELI (TC4ELI) alloy is a type of medium strength titanium alloy. By decreasing interstitial elements on the base of conventional TC4 alloy, TC4ELI alloy exhibites remarkable damage tolerance properties. This present study primarily focuses on microstructure and mechanical properties of TC4 ELI plate after three kinds of heat treatment: annealing treatment, below and above beta transus temperature (Tβ) solution following aging treatment. The results show that TC4ELI plates after annealing treatment and below Tβsolution treatment exhibite almost the same microstructure and mechanical properties, including tensile properties, fatigue crack growth rates (da/dN). Above Tβ solution and aging treatment, it leads to Widmanstaten structure with prior (3 grain, which exhibites high fatigue crack resistance and fracture toughness. Additional crack propagating path observed by SEM has been employed to disclose the microstructural influence in Widmanstaten structure.