The advent of additive manufacturing (AM), also known as 3D printing, has revolutionized the production of titanium alloys, offering significant advantages in fabricating complex geometries with enhanced mechanical properties. This study investigates the variant-specific deformation mechanisms in HIP-treated TA15 (Ti-6.5Al-2Zr-1Mo-1V) titanium alloy, fabricated via selective electron beam melting (SEBM). The alloy exhibits a dual-phase (α+β) microstructure, where six distinct α variants are formed through the β→α phase transformation following the Burgers orientation relationship. Variant selection during AM leads to a non-uniform distribution of these α variants, with α6 (22.3%) dominating due to preferential growth. Analysis of the prismatic slip Schmid factor reveals that α4–α6 variants, with higher Schmid factors (>0.45), primarily undergo prismatic slip, while α1–α3 variants, with lower Schmid factors (<0.3), rely on basal or pyramidal slip and twinning for plastic deformation. In-grain misorientation axis (IGMA) analysis further reveals strain-dependent slip transitions: pyramidal slip is activated in α1–α3 variants at lower strains, while prismatic slip becomes the dominant deformation mechanism in α4–α6 variants at higher strains. Additionally, deformation twins, primarily {10–12} extension twins (7.1%), contribute to the plasticity of hard-oriented α variants. These findings significantly enhance the understanding of the orientation-dependent deformation mechanisms in HIPed TA15 alloy and provide a crucial basis for optimizing the performance of additively-manufactured titanium alloys.

Ti₂AlNb-based alloys are potential structural materials for high-temperature applications due to their low density and superior specific strength. However, their widespread application is limited by relatively poor oxidation resistance above 700 °C. While Ti₂AlNb-based alloys exhibit promising mechanical properties, their oxidation behavior remains inadequately characterized, particularly concerning the role of Nb content. In this study, the high-temperature oxidation behavior of Ti₂AlNb-based alloys with different Nb contents was investigated at 800 °C in air. The results revealed a characteristic double-layered oxide structure consisting of an outer TiO₂ layer and inner alternating TiO₂-rich and AlNbO₄-rich sublayers. Thermodynamic calculations confirmed the favorable formation of TiO₂, Al₂O₃, Nb₂O₅, and AlNbO₄ at high temperatures. However, the reaction between Nb₂O₅ and Al₂O₃ hinders the formation of a protective Al₂O₃ layer. Increasing the Nb content was found to replace Ti atoms, reducing the diffusion rate of oxygen and simultaneously decreasing the thickness of porous TiO₂ regions. Nevertheless, the inadequate rate of aluminum diffusion inhibited adequate Al₂O₃ formation, leading to limited overall oxidation protection. These findings elucidate the composition–oxidation relationship in Ti₂AlNb-based alloys and provide valuable insights for tailoring Nb and Al contents to achieve a balanced combination of mechanical properties and high-temperature oxidation resistance.

Laser powder bed fusion (L-PBF), as one of the additive manufacturing (AM) or 3D printing techniques, has been widely used for the net-shape fabrication of high-entropy alloys (HEAs). However, microstructural defects are often present in the FeCoNiCrMn high-entropy alloy fabricated via L-PBF, which necessitate subsequent heat treatment for optimization. In this study, FeCoNiCrMn HEA samples were fabricated using L-PBF and subsequently annealed at different temperatures. The influence of heat treatment on the microstructure and mechanical properties was investigated. The results revealed that the cellular substructure remained stable at 650 °C, while at 1100 °C dislocation recovery and compositional homogenization occurred, leading to the dissolution of the cellular substructure. After annealing at 1200 °C, the elongation of the alloy increased by 82%, while the yield strength and ultimate tensile strength decreased by 37% and 10%, respectively, compared to the as-built state. The cellular substructure not only contributed to strength through dislocation strengthening but also acted as nucleation sites for subsequent twinning, resulting in improved work hardening capability. Annealing-induced grain growth and substructure elimination improved the capacity of coordinated plastic deformation, while weakening the contribution of grain rotation and twinning mechanisms.

γ-TiAl-based alloys are promising lightweight materials for high-temperature applications, but their insufficient oxidation resistance near 800 °C remains a major limitation. This study aims to clarify the short-term oxidation behavior and associated scale/interface evolution of an as-cast Ti-44Al-4Nb-1.5Cr-0.5Mo-0.1B (at.%) alloy. This composition was selected because the Nb, Cr, and Mo containing TiAl system enables alloying-element redistribution to be examined together with oxide-scale evolution. Isothermal oxidation was conducted in static air at 800 °C for 1–48 h, followed by oxidation-kinetics measurements and multiscale characterization. The mass gain increased continuously with a kinetic exponent of n = 1.77, indicating deviation from ideal parabolic behavior. After 48 h, a porous and chemically heterogeneous multilayered scale formed, comprising a TiO₂-dominated outer region, locally distributed Al-rich oxides, and nitride-containing interfacial regions. TiN and Ti₂AlN were identified together with pronounced interfacial N enrichment and localized Nb/Cr enrichment. The results indicate that a continuous compact Al-rich protective layer was not established during short-term oxidation, highlighting the importance of scale continuity and compactness in limiting oxidation of TiAl alloys near 800 °C.