2024 年 65 巻 5 号 p. 597-602
Due to its exceptional high temperature mechanical properties and low density, TiAl alloy has emerged as a promising structural material for high temperature applications. However, the inherent brittleness and susceptibility to cracking pose challenges during processing. In the additive manufacturing process of TiAl alloy, substrate preheating plays a crucial role in mitigating crack formation. This study focuses on the fabrication of crack-free Ti-48Al-2Cr-2Nb alloy via laser directed energy deposition (LDED), investigating the influence of preheating on sample cracks and microstructure. The results demonstrate that substrate preheating significantly affects the quality of formed samples. Without preheating, numerous cracks are observed in the samples; however, their severity gradually decreases with increasing preheating temperature. Notably, when the substrate was heated to 400°C, no cracks were detected in the samples. Moreover, higher preheating temperature lead to reduced grain length-diameter ratio and partial equiaxed crystal formation along with increased average grain size and α2 phase proportion while decreasing average orientation difference slightly. The microhardness exhibited a subtle declining tendency. With an increase in the proportion of α2 phase, the stress generated between different phases is reduced. Additionally, increasing the preheating temperature reduces dislocation density and releases stress, thereby inhibiting crack generation.
