Intermetallic TiAl alloys have found applications in the aerospace and automotive fields. Nevertheless, to satisfy the increasingly complex environmental requirements, these lightweight alloys must be improved particularly in strength and ductility. Additive manufacturing (AM) exhibits a rapid solidification rate and may strengthen intermetallic TiAl alloys. In this study, an additively manufactured (AMed) Ti-48Al-8 Nb alloy with fine formability was successfully fabricated by optimizing the power used during directed energy deposition. The preferential crystal plane for the obtained alloy is {111}γ due to its lowest surface energy, and the presence of the thermal gradient during the AM process results in the alloy growing along the building direction. The TiAl alloy AMed at 500 W delivers an excellent tensile strength of 880 MPa that is 1.71 times higher than that of its as-cast counterpart, as well as elongation of 0.7% at room temperature. The superior properties of this alloy are due to the formation of numerous deformation twins during tensile deformation at room temperature that enables twin intersections to produce high-density nano-twins while contributing to stress release. Moreover, the AMed TiAl alloy exhibits outstanding high-temperature strength retention performance.

中文翻译：

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通过定向能量沉积增材制造高含铌 TiAl 合金的强度和延展性


金属间化合物TiAl合金已在航空航天和汽车领域得到应用。然而，为了满足日益复杂的环境要求，必须改进这些轻质合金，特别是在强度和延展性方面。增材制造 (AM) 具有快速凝固速率，可以强化金属间 TiAl 合金。在这项研究中，通过优化定向能量沉积过程中使用的功率，成功制造了具有良好成形性的增材制造 (AMed) Ti-48Al-8Nb 合金。由于其最低的表面能，所得合金的优先晶面为{111}γ，并且增材制造过程中热梯度的存在导致合金沿构建方向生长。 TiAl 合金 AMed 在 500W 下具有 880MPa 的优异抗拉强度，是铸态材料的 1.71 倍，室温伸长率为 0.7%。该合金的优越性能是由于在室温拉伸变形过程中形成大量变形孪晶，使孪晶相交处产生高密度纳米孪晶，同时有助于应力释放。此外，AMed TiAl合金表现出出色的高温强度保持性能。