气雾化球形钛合金粉末内部气孔的形成机制研究

It is the gas-atomized spherical titanium powders that become the important industrial raw materials to produce titanium components by 3D printing. The gas-atomized titanium powders, however, normally contain gas-pore defect arising from gas entrapment and subsequently such defect inferiors the mechanical properties of 3D-printed products. It is indeed a critical problem needed to be solved in the powder metallurgy area. Solving this problem needs to study the break-up mode of the metal liquid droplet and the interplay with its rapid cooling during atomizing, while research in this respect has not been reported. The applicants have produced spherical Ti-6Al-4V powders by gas atomizing and found entrapped gas pores in the powders. In this study, the applicants propose to analyze the droplet break-up with its liquid-state rapid cooling process, establishing a theoretical model for gas-pore formation and control for gas-atomized titanium powders. Characterize powder microstructures and analyze the effect of technique parameter on the gas porosity in powders by gas atomizing. On the basis of data, the model will be verified and further improved. Afterwards, the applicants will disclose the procedure and mechanism of titanium liquid flow break-up and gas entrapment in the powders. According to the theoretical model, the atomizing technique will be improved and suggestions to control the gas entrapment problem will be released by carefully governing the droplet break-up and its rapid cooling times. Additionally, the properties of powders gas atomized before and after atomizing technique improvement will be also evaluated by 3D printing, respectively.

气雾化球形钛合金粉末是3D打印钛合金零件的重要基础原料。然而，在气雾化制备钛合金粉末过程中，雾化气体容易陷入粉末内部形成气孔缺陷，从而严重影响其3D打印制品的力学性能，成为目前粉末冶金领域亟需解决的问题。解决粉末气孔问题的关键在于分析气雾化过程中金属液滴的破碎过程及其快速冷却对该过程的影响，而关于这方面的研究未见报道。申请人已采用气雾化技术制备钛合金（Ti-6Al-4V）粉末，并观察到粉末内部气孔缺陷的现象。本课题拟结合液滴破碎与其液态阶段快速冷却的分析，建立粉末气孔形成及控制的理论模型；基于模型制备钛合金粉末，表征粉末性能，分析工艺参数对粉末气孔形成的影响，根据数据验证并优化模型；确定钛合金液滴最终的破碎过程，揭示粉末气孔形成机制，从而指导气雾化工艺，控制液滴破碎及其快速冷却过程的时间，提供解决气雾化粉末气孔问题的建议；最后，对雾化工艺改进前后制备的钛合金粉末进行3D打印评估和分析。

气雾化球形钛合金粉末是3D打印钛合金零件的重要基础原料。然而，在气雾化制备钛合金粉末过程中，雾化气体容易陷入粉末内部形成气孔缺陷，从而严重影响其3D打印制品的力学性能，成为目前粉末冶金领域亟需解决的问题。解决粉末气孔问题的关键在于分析气雾化过程中金属液滴的破碎过程及其快速冷却对该过程的影响，而关于这方面的研究未见报道。申请人已采用气雾化技术制备钛合金（Ti-6Al-4V）粉末，并观察到粉末内部气孔缺陷的现象。本课题拟结合液滴破碎与其液态阶段快速冷却的分析，建立粉末气孔形成及控制的理论模型；基于模型制备钛合金粉末，表征粉末性能，分析工艺参数对粉末气孔形成的影响，根据数据验证并优化模型；确定钛合金液滴最终的破碎过程，揭示粉末气孔形成机制，从而指导气雾化工艺，控制液滴破碎及其快速冷却过程的时间，提供解决气雾化粉末气孔问题的建议；利用雾化工艺改进前后制备的钛合金粉末，对其进行3D打印评估和分析。