Abstract

The crack formation mechanisms of Ti–48Al–2Cr–2Nb single tracks processed by laser powder bed fusion were extensively investigated in a wide range of laser powers and scan speeds. The crack patterns were categorized by their directionalities, which were parallel (longitudinal crack) and/or perpendicular (transverse crack) to the scan direction. For the representative process conditions of the keyhole, transition, and conduction modes, cracking behaviors were characterized by combining the fractography and the microstructural analysis. Further, thermal-mechanical finite element method simulations were performed to predict the distribution of temperatures and thermal stresses during the melt pool formation. On the basis of the combined results, the cracks formed in keyhole, transition, and conduction modes were clarified as a solidification crack and/or a thermal crack. In addition, the formation of these cracks was thoroughly understood in terms of thermal stresses and microstructural factors that affect the crack susceptibility. Finally, comprehensive mechanisms responsible for cracking of Ti–48Al–2Cr–2Nb single tracks under laser powder bed fusion were proposed for different process conditions (the keyhole, transition and conduction modes).

Graphic Abstract

中文翻译：

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了解激光粉末床熔合过程中Ti–48Al–2Cr–2Nb单径道的裂纹形成机理

摘要

在广泛的激光功率和扫描速度下，广泛研究了通过激光粉末床熔合处理的Ti–48Al–2Cr–2Nb单道裂纹形成机理。裂纹图案按其方向分类，这些方向与扫描方向平行（纵向裂纹）和/或垂直（横向裂纹）。对于锁孔，过渡和传导模式的代表性工艺条件，通过结合形貌和显微组织分析来表征裂纹行为。此外，进行了热机械有限元方法模拟，以预测熔池形成过程中温度和热应力的分布。根据综合结果，在锁孔，过渡，传导模式明确为凝固裂纹和/或热裂纹。此外，通过影响应力敏感性的热应力和微观结构因素，可以充分理解这些裂缝的形成。最后，针对不同工艺条件（锁孔，过渡和传导模式），提出了在激光粉末床熔合下造成Ti–48Al–2Cr–2Nb单道裂纹破裂的综合机制。

图形摘要