在這項研究中，透過雷射箔材列印 (LFP) 技術製造過程中，研究了兩種掃描策略對Ti-6Al-4V 零件殘留應力的影響，其掃描策略為線圖案掃描 (LPS) 和點圖案掃描 (SPS)。使用有限元素方法 (FEM) 進行三維固體熱傳與固體力學耦合的模擬，結果包括殘留應力、熔池形態和變形，並且與實驗數據進行相互驗證，增加模擬的可靠性，其中熔池尺寸的模擬和實驗數據顯示出小於11.6%的偏差。另外使用X射線衍射 (XRD) 測量殘留應力，而XRD測量結果和模擬殘留應力皆顯示，透過使用SPS策略可將LFP製造零件的殘留應力降低至530 MPa，而使用LPS策略的LFP製造零件殘留應力為1160 MPa，因此結果表明使用SPS策略可以顯著地降低LFP製造零件的殘留應力。另外，零件橫截面SEM圖像中的微結構以及XRD圖表示，使用LPS策略製造的零件主要以α′相組成，而使用SPS策略製造的零件則由α相和β相組成。此外使用背向散射電子繞射技術 (EBSD) 分析晶粒分佈、晶粒尺寸以及極圖，並且相互比較兩種掃描策略製造零件的分析結果，其結果表示使用SPS策略製造的零件在XY和YZ方向皆觀測出較大的晶粒尺寸，這種晶粒尺寸差異的主要原因是由於製造過程中不同冷卻率所造成的。在所有極圖中皆表明{001}為主要的優選生長方向，而{111}和{110}為次要的生長方向。

In this study, the effect of two scan strategies, line pattern scanning (LPS) and spot pattern scanning (SPS), on residual stress was studied for fabricating Ti-6Al-4V parts using the laser-foil-printing (LFP) process. Three-dimensional coupled thermal-mechanical simulations were conducted using the finite-element method (FEM) and compared with experimental data, including residual stress, melt pool morphology, and deformation. The melt pool dimensions in both experiments and simulations showed a small deviation of less than 11.6%. Residual stress was measured using X-ray diffraction (XRD), and the XRD measurements and simulated residual stresses revealed that the SPS strategy reduced residual stresses to approximately 530 MPa, whereas the LPS strategy resulted in residual stresses of around 1160 MPa. Thus, the SPS strategy can significantly reduce residual stress in LFP-fabricated Ti-6Al-4V parts. Besides, cross-section SEM images and XRD patterns indicate that those parts made using LPS strategy were dominated by α’ phase whereas parts fabricated using SPS strategy were consisted of α phase and prior β phase due to re-melting. Moreover, using electron backscatter diffraction (EBSD) to analysis the grain distribution and grain size, the results show that the parts fabricated using the SPS strategy exhibited larger grain sizes in both the XY and YZ directions compared to those fabricated using the LPS strategy. This grain size difference can be mainly attributed to different cooling rates during fabrication process. All of pole figures indicated that a preferred orientation along {001}, with minor orientations along {111} and {110}.

[1] ZC Fang, ZL Wu, CG Huang, CW Wu, Review on residual stress in selective laser melting additive manufacturing of alloy parts. Optics and Laser Technology, vol. 129, 2020.
[2] Y Zhang, L Wu, X Guo, S Kane, Y Deng, YG Jung, JH Lee, J Zhang, Additive manufacturing of metallic materials: a review. J. of Materials Engineering and Performance, vol. 27, p. 1-13, 2018.
[3] C Chen, Y Shen, HL Tsai, A foil-based additive manufacturing technology for metal parts. J. Manufacturing Science and Engineering, vol. 139, 2017.
[4] Y Li, Y Shen, MC Leu, HL Tsai, Building Zr-based metallic glass part on Ti-6Al-4V substrate by laser-foil-printing additive manufacturing. Acta Materialia, vol. 144, p. 810-821, 2018.
[5] CH Hung, A Sutton, Y Li, Y Shen, HL Tsai, MC Leu, Enhanced mechanical properties for 304L stainless steel parts fabricated by laser foil-printing additive manufacturing. J. Manufacturing Processes, vol. 45, p. 438-446, 2019.
[6] CH Hung, A Sutton, Y Li, WT Chen, X Gong, H Pan, HL Tsai, MC Leu, Aluminum parts fabricated by laser-foil-printing additive manufacturing: processing, microstructure, and mechanical properties. J. Materials. vol. 13, p. 414, 2020.
[7] H Jia, H Sun, H Wang, Y Wu, H Wang, Scanning strategy in selective laser melting (SLM): a review. J. Advanced Manufacturing Technology, vol. 113, p. 2413-2435, 2021.
[8] J Jhabvala, E Boillat, T Antignac, R Glardon, On the effect of scanning strategies in the selective laser melting process. Virtual and physical prototyping, vol. 5, p. 99-109, 2010.
[9] X Yan, J Pang, Y Jing, Ultrasonic Measurement of Stress in SLM 316L Stainless Steel Forming Parts Manufactured Using Different Scanning Strategies. J. Materials, vol. 12, 2019.
[10] P Promoppatum, SC Yao, Influence of scanning length and energy input on residual stress reduction in metal additive manufacturing: Numerical and experimental studies. J. Manufacturing Processes, vol. 49, p. 247-259, 2020.
[11] MF Zaeh, G Branner, Investigations on residual stresses and deformations in selective laser melting. Production Engineering, vol. 4, p. 35-45, 2010.
[12] SG Chen, HJ Gao, YD Zhang, Q Wu, ZH Gao, X Zhou, Review on residual stresses in metal additive manufacturing: formation mechanisms, parameter dependencies, prediction and control approaches. J. Materials Research and Technology, vol. 17, p. 2950-2974, 2022.
[13] Y Lu, S Wu, Y Gan, T Huang, C Yang, J Lin, J Lin, Study on the microstructure, mechanical property and residual stress of SLM Inconel-718 alloy manufactured by differing island scanning strategy. Optics & Laser Technology, vol. 75, p. 197-206, 2015.
[14] D Ramos, F Belblidia, J Sienz, New scanning strategy to reduce warpage in additive manufacturing. Additive Manufacturing, vol. 28, p. 554-564, 2019.
[15] W Zhang, M Tong, NM Harrison, Scanning strategies effect on temperature, residual stress and deformation by multi-laser beam powder bed fusion manufacturing. Additive Manufacturing, vol. 36, 2020.
[16] M Guo, Y Ye, X Jiang, L Wang, Microstructure, Mechanical Properties and Residual Stress of Selective Laser Melted AlSi10Mg. J. Materials Engineering and Performance, vol. 28, p. 6753-6760, 2019.
[17] D Buchbinder, W Meiners, N Pirch, K Wissenbach, Investigation on reducing distortion by preheating during manufacture of aluminum components using selective laser melting. J. Laser Applications, vol. 26, 2014.
[18] L Parry, IA Ashcroft, RD Wildman, Understanding the effect of laser scan strategy on residual stress in selective laser melting through thermo-mechanical simulation. Additive Manufacturing, vol. 12, p. 1-15, 2016.
[19] AM Jonaet, HS Park, LC Myung, Prediction of residual stress and deformation based on the temperature distribution in 3D-printed parts. J. Advanced Manufacturing Technology, vol. 113, p. 2227-2242, 2021.
[20] X Zhao, A Iyer, P Promoppatum, SC Yao, Numerical modeling of the thermal behavior and residual stress in the direct metal laser sintering process of titanium alloy products. Additive Manufacturing, vol. 14, p. 126-136, 2017.
[21] K Ökten, A Biyikoğlu, Development of thermal model for the determination of SLM process parameters. Optics & Laser Technology, vol. 137, 2021.
[22] G Vander Voort, EP Manilova, Metallographic etching of Aluminum and its alloys, 2009.
[23] JV Bernier, JS Park, AL Pilchak, MG Glavicic, MP Miller, Measuring stress distributions in Ti-6Al-4V using synchrotron x-ray diffraction. Metallurgical and Materials Transactions A, vol. 39, p. 3120-3133, 2008.
[24] SLR Da Silva, LO Kerber, L Amaral, CA Dos Santos, X-ray diffraction measurements of plasma-nitrided Ti–6Al–4V. Surface and Coatings Technology, vol. 116, p. 342-346, 1999.
[25] B Eigenmann, E Macherauch, Röntgenographische untersuchung von spannungszuständen in werkstoffen. Materials Science & Engineering Technology, vol. 26, p. 148-160, 1995.
[26] JX Bao, J Xu, JN Bai, SD Lv, DB Shan, B Guo, Mechanical behavior and shear banding of electropulsing-assisted micro-scale shear-compression in Ti-6Al-4V alloy. Material Science & Engineering, vol. 771, 2020).
[27] SY Boakye, K Kim, J Kim, JS Lee, J Choi, SY Anaman, HH Cho, A microstructural, mechanical and electrochemical/stress corrosion cracking investigation of a Cr-modified Tie6Ale4V alloy. Journal of Materials Research and Technology, vol. 25, p. 354-368, 2023.
[28] AK Gain, LC Zhang, S Lim, Tribological behavior of Ti–6Al–4V alloy: Subsurface structure, damage mechanism and mechanical properties. Wear, vol. 464, 2021.
[29] M.J. Phasha, A.S. Bolokang, P.E. Ngoepe, Solid-state transformation in nanocrystalline Ti induced by ball milling. Materials Letters, vol. 64, p. 1215-1218, 2010.
[30] Z Zhang, M Lin, DHL Seng, SL Teo, F Wei, HR Tan, AKH Cheong, SH Lim, J Pan, Fatigue life enhancement in alpha/beta Ti–6Al–4V after shot peening: An EBSD and TEM crystallographic orientation mapping study of surface layer. Materialia, vol. 12, 2020.
[31] NC Levkulich, An Experimental Investigation of Residual Stress Development during Selective Laser Melting of Ti-6Al-4V. Wright State University, 2017.
[32] B Vrancken, Study of residual stresses in selective laser melting. 2016.
[33] Q Chen, X Liang, D Hayduke, J Liu, L Cheng, J Oskin, R Whitmore, AC To, An inherent strain based multiscale modeling framework for simulating part-scale residual deformation for direct metal laser sintering. Additive Manufacturing, vol. 28, p. 406-418, 2019.
[34] Z Gan, Y Lian, SE Lin, KK Jones, WK Liu, GJ Wagner, Benchmark Study of Thermal Behavior, Surface Topography, and Dendritic Microstructure in Selective Laser Melting of Inconel 625. Integrating Materials and Manufacturing Innovation, vol. 8, p. 178-193, 2019.
[35] C Li, ZY Liu, XY Fang, YB Guo, Residual stress in metal additive manufacturing. Procedia CIRP, vol. 71, p. 348-353, 2018.
[36] C Leyens, M Peters, Titanium and titanium alloys: fundamentals and applications. John Wiley & Sons, 2003.
[37] R Pederson, Microstructure and phase transformation of Ti-6Al-4V. Luleå University of Technology, 2002.
[38] D Agius, KI Kourousis, C Wallbrink, T Song, Cyclic plasticity and microstructure of as-built SLM Ti-6Al-4V: The effect of build orientation. Materials Science and Engineering A, vol. 701, p. 85-100, 2017.
[39] H Ali, L Ma, H Ghadbeigi, K Mumtaz, In-situ residual stress reduction, martensitic decomposition and mechanical properties enhancement through high temperature powder bed pre-heating of Selective Laser Melted Ti6Al4V. Materials Science & Engineering A, vol. 695, p. 211-220, 2017.
[40] FR Kaschel, RK Vijayaraghavan, A Shmeliov, EK McCarthy, M Canavan, PJ McNally, DP Dowling, V Nicolosi, M Celikin, Mechanism of stress relaxation and phase transformation in additively manufactured Ti-6Al-4V via in situ high temperature XRD and TEM analyses. Acta Materialia, vol. 188, p. 720-732, 2020.
[41] M Neikter, P Åkerfeldt, R Pederson, ML Antti, V Sandell, Microstructural characterization and comparison of Ti-6Al-4V manufactured with different additive manufacturing processes. Material Characterization, vol. 143, p.68-75, 2018.
[42] E Onal, AE Medvedev, MA Leeflang, A Molotnikov, AA Zadpoor, Novel microstructural features of selective laser melted lattice struts fabricated with single point exposure scanning. Additive Manufacturing, vol. 29, 2019.