Cavity-induced bubbles and pore formation of laser direct energy deposited titanium alloy: Influence of powder melting degree

IF 10.3 1区工程技术 Q1 ENGINEERING, MANUFACTURING

Additive manufacturing Pub Date : 2025-04-25 DOI:10.1016/j.addma.2025.104792

Mingyuan Chen , Jikui Zhang , Qiulin Qu , Shuquan Zhang , Dong Liu

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Abstract

Porosity defects and their impact on fatigue performance have become one of the key issues in the widespread application of laser direct energy deposited titanium alloy components. The present work focuses on the cavity evolution and bubble generation process of unmelted, partially melted and fully melted powder entering the melt pool. Firstly, an equivalent experiment, ice particle with different melting degree impact water, was designed and conducted on the basis of similarity criterion in fluid mechanics. Secondly, a numerical model of powder impingement melt pool was established by using dynamic mesh method to simulate the evolution of cavity with different melting degree. Finally, a deposition processing with different melting states of the powder, by adjusting the angle and height of the powder feeding nozzle, was engaged to verify the influence of the melting states of the powder on the pore formation. The equivalent test and simulation results show that for the unmelted powder with large diameter and high velocity, the impacted cavity pinches off near the surface and induces gas entrainment and bubbles formation. For comparison, the fully melted powder enters the melt pool with a crater-shaped cavity which collapsed in a contraction mode and has not residual gas and bubbles. The surrounding liquid surface of partially melted powder changes the shape of the cavity and extended the time of collapse. With the increase of melting degree of powder, the collapse of cavity changes from the pinch-off to contraction mode, which avoids the generation of cavity-induced bubbles. The deposition experimental results show that both the pore size and porosity of the deposited specimen decrease with the increase of powder melting degree. This study is significant to clarify of the mechanism of porosity formation and decrease of porosity defects of laser direct energy deposited titanium alloy.

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激光直接能量沉积钛合金的空腔诱导气泡和孔隙形成：粉末熔化程度的影响

孔隙缺陷及其对疲劳性能的影响已成为激光直接能量沉积钛合金部件广泛应用的关键问题之一。本文重点研究了未熔化、部分熔化和完全熔化粉末进入熔池的空腔演化和气泡产生过程。首先，根据流体力学相似准则，设计并进行了不同融化度冰粒撞击水的等效实验。其次，采用动态网格法建立了粉末撞击熔池的数值模型，模拟了不同熔化程度的空腔的演化过程。最后，通过调整进料喷嘴的角度和高度，进行粉末不同熔化状态的沉积工艺，验证粉末熔化状态对孔隙形成的影响。等效试验和模拟结果表明，对于大直径、高速度的未熔化粉末，冲击空腔在接近表面处发生挤压，引起气体夹带和气泡的形成；相比之下，完全熔化的粉末进入熔池时带有一个以收缩方式塌陷的坑形空腔，没有残余气体和气泡。部分熔化粉末的周围液面改变了空腔的形状，延长了塌陷时间。随着粉末熔化程度的增加，空腔的坍塌由掐断模式转变为收缩模式，避免了空腔诱导气泡的产生。沉积实验结果表明，随着粉末熔化程度的增加，沉积试样的孔径和孔隙率均减小。该研究对阐明激光直接能沉积钛合金气孔形成机理和减少气孔缺陷具有重要意义。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Additive manufacturing Materials Science-General Materials Science

CiteScore

19.80

自引率

12.70%

发文量

648

审稿时长

35 days

期刊介绍： Additive Manufacturing stands as a peer-reviewed journal dedicated to delivering high-quality research papers and reviews in the field of additive manufacturing, serving both academia and industry leaders. The journal's objective is to recognize the innovative essence of additive manufacturing and its diverse applications, providing a comprehensive overview of current developments and future prospects. The transformative potential of additive manufacturing technologies in product design and manufacturing is poised to disrupt traditional approaches. In response to this paradigm shift, a distinctive and comprehensive publication outlet was essential. Additive Manufacturing fulfills this need, offering a platform for engineers, materials scientists, and practitioners across academia and various industries to document and share innovations in these evolving technologies.