Influence of laser post-processing on pore evolution of Ti–6Al–4V alloy by laser powder bed fusion

• Published in: Journal of alloys and compounds Vol. 818; p. 152845
• Main Authors: Shen, Bingnan, Li, Hui, Liu, Sheng, Zou, Jing, Shen, Shengnan, Wang, Yinghe, Zhang, Tao, Zhang, Dongqi, Chen, Yinghua, Qi, Haiqin
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.03.2020; Elsevier BV
• Subjects: Additive manufacturing; Computed tomography; Computer simulation; Evolution; Finite element method; Flux density; Laser beams; Laser powder bed fusion; Lasers; Level-set method; Mass transfer; Mathematical models; Morphology; Pore evolution; Porosity; Post-processing; Powder beds; Process parameters; Titanium base alloys; Ti–6Al–4V alloy; Void fraction; Laser powder bed fusion; Ti–6Al–4V alloy; Additive manufacturing; Level-set method; Pore evolution
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.152845

In laser powder bed fusion (LPBF) processes, critical defect issues such as porosity limit the quality of the fabricated part. This work investigates the mechanism of pore evolution during the laser post-processing of an LPBF part. A laser beam was utilized to scan the top surface of a Ti–6Al–4V alloy part. The morphologies of the internal layers as well as the distribution of the porosity inside the Ti–6Al–4V sample were experimentally measured and compared using micro-computed tomography (micro-CT). It was found that the void fraction was significantly decreased, from 2.51% to 0.77%, by laser post-processing. A multi-physics coupled finite element model based on the Level-set method was built to analyze the evolution mechanism of the pore. This model simulated the effects of the energy density, Marangoni flow and mass transfer on the pore evolution. Typical processes were studied in detail, and a table summarizing the pore evolution under different post-processing parameters is given. [Display omitted] •Internal morphologies of Ti–6Al–4V sample measured by micro-CT.•A Level-set model is built to analyze the evolution mechanism of porosity.•Mass transfer on the bubble surface is the essence of pore evolution.•Main factor impacting gas bubble rising is from Marangoni effect rather than buoyancy.