Polozov Igor, Starikov Kirill, Popovich Anatoly, Sufiiarov Vadim
Institute of Mechanical Engineering, Materials, and Transport, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia.
Materials (Basel). 2021 Aug 30;14(17):4946. doi: 10.3390/ma14174946.
Titanium orthorhombic alloys based on intermetallic TiAlNb-phase are attractive materials for lightweight high-temperature applications. However, conventional manufacturing of TiAlNb-based alloys is costly and labor-consuming. Additive Manufacturing is an attractive way of producing parts from TiAlNb-based alloys. High-temperature substrate preheating during Selective Laser Melting is required to obtain crack-free intermetallic alloys. Due to the nature of substrate preheating, the temperature profile along the build height might be uneven leading to inhomogeneous microstructure and defects. The microstructural homogeneity of the alloy along the build direction was evaluated. The feasibility of mitigating the microstructural inhomogeneity was investigated by fabricating TiAlNb-alloy samples with graded microstructure and subjecting them to annealing. Hot isostatic pressing allowed us to achieve a homogeneous microstructure, eliminate residual micro defects, and improve mechanical properties with tensile strength reaching 1027 MPa and 860 MPa at room temperature and 650 °C, correspondingly. Annealing of the microstructurally graded alloy at 1050 °C allowed us to obtain a homogeneous B2 + O microstructure with a uniform microhardness distribution. The results of the study showed that the microstructural inhomogeneity of the titanium orthorhombic alloy obtained by SLM can be mitigated by annealing or hot isostatic pressing. Additionally, it was shown that by applying multiple-laser exposure for processing each layer it is possible to locally tailor the phase volume and morphology and achieve microstructure and properties similar to the Ti2AlNb-alloy obtained at higher preheating temperatures.
基于金属间化合物TiAlNb相的正交钛合金是用于轻质高温应用的有吸引力的材料。然而，传统的TiAlNb基合金制造成本高且耗费人力。增材制造是由TiAlNb基合金生产零件的一种有吸引力的方法。选择性激光熔化过程中需要进行高温基板预热以获得无裂纹的金属间合金。由于基板预热的性质，沿构建高度的温度分布可能不均匀，导致微观结构不均匀和出现缺陷。评估了合金沿构建方向的微观结构均匀性。通过制造具有梯度微观结构的TiAlNb合金样品并对其进行退火，研究了减轻微观结构不均匀性的可行性。热等静压使我们能够获得均匀的微观结构，消除残余微观缺陷，并改善力学性能，室温及650°C下的拉伸强度分别达到1027MPa和860MPa。在1050°C对微观结构梯度合金进行退火，使我们能够获得具有均匀显微硬度分布的均匀B2 + O微观结构。研究结果表明，通过退火或热等静压可以减轻选择性激光熔化获得的正交钛合金的微观结构不均匀性。此外，研究表明，通过对每层应用多激光曝光，可以局部调整相体积和形态，并获得与在较高预热温度下获得的Ti2AlNb合金相似的微观结构和性能。
