Residual stress reduction in Ti-6Al-4V parts fabricated by laser-foil-printing process

• Published in: Optics and laser technology Vol. 177; p. 111157
• Main Authors: Huang, Ting-Chun, Hung, Chia-Hung, Lin, Yong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2024
• Subjects: Additive manufacturing; Laser foil printing; Residual stress; Ti-6Al-4V; Additive manufacturing; Ti-6Al-4V; Laser foil printing; Residual stress
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2024.111157

•The residual stress of parts using SPS in LFP was substantially reduced by 56 % from 1162 to 530 MPa compared to using LPS.•3D thermal-mechanical FEM models were developed to collaborate the practical residual stress of Ti64 parts in LFP.•The parts fabricated using SPS in LFP had coarser grains compared to using LPS because of different cooling rates. In this study, the effects of two scan strategies, line pattern scanning (LPS) and spot pattern scanning (SPS), on alleviating the accumulation of residual stress were investigated for the fabrication of Ti-6Al-4V (Ti64) parts using a laser-foil-printing (LFP) additive manufacturing process. The residual stresses in the parts prepared using SPS in LFP were substantially reduced (by 56 %) from 1161.8 to 530 MPa compared to the use of LPS alone, as determined by X-ray diffractometry (XRD). Three-dimensionally coupled thermal–mechanical models were developed to combine the practical residual stress, melt pool, and deformation of Ti64 parts in LFP using the finite-element method (FEM), which exhibited a minor deviation of less than 11.6 % between the experimental and simulated results. Additionally, cross-sectional microstructural images and XRD patterns indicate that the α′ phase dominates parts fabricated by LPS whereas those fabricated using SPS consist of the α phase and the prior β phase due to the effect of remelting. Electron backscatter diffraction (EBSD) was used to analyze the grain distribution, preferred grain orientation, and grain size, which revealed that the parts fabricated using SPS had larger grains in both the XY and YZ planes than those fabricated using LPS, which is attributable to different cooling rates during the solidification process.