Fatigue and damage tolerance performance of additively-manufactured titanium alloys for structural application: A comprehensive review

Titanium (Ti) alloys have emerged as one of the most sought-after metallic materials for additive manufacturing (AM). This originates from the unparalleled synergy of AM's capability to produce intricate geometries and the superior mechanical properties and corrosion resistance inherent to Ti alloys. Despite these benefits, AM Ti alloys continue to face persistent challenges that hinder their in-service reliability and broader adoption. Unlike conventionally manufacturing, AM introduces unique microstructural features such as non-uniform residual stresses and inhomogeneous grain structures, which often result in pronounced variability in material properties. Crucially, this variability underscores an urgent need for thorough performance evaluation of AM-produced parts, especially for critical structural applications where safety and durability are paramount. Previous reviews have broadly addressed AM Ti alloys' static properties and general processing challenges. In contrast, this review takes a comprehensive approach to examine the dynamic performance aspects—specifically, fatigue and damage tolerance—which remain insufficiently summarized yet vital for real-world applications. It deepens into the underlying mechanisms governing these properties, emphasizing the influence of key defects (e.g., porosity, segregation) as well as microstructural characteristics such as grain morphology and residual stresses. Additionally, this work expands the discussion to assess the behavior of AM Ti alloys under extreme environmental conditions (high-temperature and cryogenic operations), which are increasing demand in the automotive and energy sectors. By providing a detailed evaluation of these critical aspects, this review aims to bridge existing knowledge gaps, offering actionable insights to refine AM Ti alloy processing and enhance their structural reliability for demanding applications.