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研究生: 王昱翔
Wang, Yu-Hsiang
論文名稱: 以機器學習製程圖引導雷射箔材列印製程中Inconel 625機械性質之評估
Using Machine Learning-Based Process Map to Guide Evaluation of Inconel 625 Mechanical Properties in Laser Foil Printing
指導教授: 洪嘉宏
Hung, Chia-Hung
學位類別: 碩士
Master
系所名稱: 工學院 - 機械工程學系
Department of Mechanical Engineering
論文出版年: 2026
畢業學年度: 114
語文別: 英文
論文頁數: 47
中文關鍵詞: 雷射箔材列印機器學習製程圖英高鎳合金625
外文關鍵詞: Laser Foil Printing, Machine Learning, Process Map, Inconel 625
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  • Inconel 625 為一種廣泛應用於航太、能源與化工產業之鎳基超合金,具有優異之高溫強度與耐腐蝕性能。然而,相較於粉末式積層製造技術,其於新興之雷射箔材列印(Laser Foil Printing, LFP)製程中的熔池行為、製程穩定性與機械性質仍缺乏系統性研究。傳統製程圖多仰賴大量試誤實驗或多項式迴歸模型,難以有效描述雷射製程中高度非線性的熱流與熔池演化行為。本研究建立一套以機器學習為基礎之製程圖譜,用以引導 Inconel 625 於雷射箔材列印製程中的參數選擇與機械性質評估。透過 32 組單道熔池實驗資料,採用梯度提升回歸(Gradient Boosting Regression, GBR)模型分別預測熔池深度與寬度,其預測決定係數(R²)分別達 0.859 與 0.793,平均絕對誤差分別為 22.25 μm 與 19.83 μm。從實驗結果可看出比起二次與三次多項式迴歸模型,基於 GBR 預測結果建立之製程圖更加的準確,可清楚區分熔融不足(lack-of-fusion)、導熱模式(conduction)與鑰孔模式(keyhole)等不同熔池行為區域。依據製程圖,選擇三組導熱模式參數,其熔池深度與箔材厚度比(D/T)分別約為 1.3、1.5 與 1.7,並搭配一組鑰孔模式參數進行五層堆疊驗證與機械性質測試。導熱模式試片展現穩定且一致之熔池形貌,層間結合良好,孔隙率均低於 0.05%。拉伸測試結果顯示,導熱模式試片於 X 與 Y 方向皆具有穩定且優異之機械性質,其極限抗拉強度介於 888–988 MPa,降伏強度為 708–759 MPa,伸長率達 35–41%,顯示在導熱模式範圍內,熔池深度變化對機械性質影響有限。相較之下,鍵孔模式試片雖因晶粒細化而維持較高強度,但因大量氣孔生成、高角度晶界比例上升及顯著動態回復效應,導致伸長率顯著下降至 32–34%,呈現明顯之強度–延性取捨行為。電子背向散射繞射(EBSD)與 X 光繞射(XRD)分析顯示,導熱模式試片具有均勻之柱狀晶結構、適中的低角度晶界比例、明顯 <001> 纖維織構及足夠之位錯密度,為其優異強延性平衡之主要原因。本研究證實以少量單道實驗資料結合梯度提升回歸模型,即可有效建立高可信度之製程圖,並快速鎖定雷射箔材列印 Inconel 625 的穩定製程窗口。此機器學習導向之製程設計流程,不僅提升參數選擇效率,亦為高性能鎳基超合金之積層製造提供一條可靠且具工程實用價值的最佳化方法。

    Inconel 625 is one of the most extensively studied nickel-based superalloys in powder-based additive manufacturing. In contrast, its processing characteristics and resulting properties in the emerging foil-feedstock based Laser Foil Printing (LFP) process remain largely unexplored. This study develops a machine learning-based process map for LFP of Inconel 625 using 32 single-track experiments. The Gradient Boosting Regression (GBR) model achieved R^2 values of 0.859 (melt pool depth) and 0.793 (melt pool width) with mean absolute errors of 22.25 μm and 19.83 μm, respectively. Compared to second- and third-order polynomial regressions, GBR demonstrated markedly superior performance in capturing nonlinear melt pool dynamics and accurately delineating lack-of-fusion, conduction, and keyhole regimes, thereby enabling a high-fidelity process map. Three conduction-mode parameter sets targeting depth-to-foil thickness (D/T) ratios of ~1.3, 1.5, and 1.7, together with one keyhole-mode set, were selected from the GBR-based process map for multi-layer validation. Conduction-mode builds from the validation experiments exhibited uniform melt pools, excellent interlayer bonding, and ultra-low porosity (<0.05%). Tensile properties were outstanding and consistent across the conduction regime: ultimate tensile strength 888-988 MPa, yield strength 708-759 MPa, and elongation 35-41%. The keyhole-mode specimen retained comparable strength but exhibited significantly reduced elongation (32-34%) due to large gas pores, increased high-angle grain boundary fraction, and excessive recovery. EBSD and XRD analyses confirmed that conduction-mode samples possessed uniform columnar grains, moderate low-angle grain boundary fractions, strong <001> fiber texture, and sufficient dislocation density, collectively delivering superior strength-ductility balance. This work demonstrates that GBR-driven process mapping using minimal single-track data enables rapid and reliable identification of robust processing windows, providing an efficient parameter optimization pathway for producing defect-free, high-performance Inconel 625 components via Laser Foil Printing.

    Abstract i 中文摘要 ii Chapter 1 Introduction 1 1.1 Background and Motivation 1 1.2 Laser Foil Printing and its Advantages 1 1.3 Challenges in Process Window Identification for LFP 2 1.4 Machine Learning -Based Process Mapping 2 1.5 Research Objectives 3 1.6 Organization of This Thesis 3 Chapter 2 Experimental Setup and Methods 5 2.1 Laser Foil Printing Process and Materials 5 2.2 Laser Foil Printing System Configuration 6 2.3 Single Track Experiments and Data Collection 8 2.4 Machine Learning Model Development and Process Map Construction 8 2.5 Multi-Layer Fabrication and Tensile Specimen Preparation 11 2.6 Microstructural and Mechanical Charactrization 12 Chapter 3 Results and Discussion 13 3.1 Performance of Machine Learning Models and Process Map Validation 13 3.2 Melt Pool Morphology and Porosity in Multi-Layer Builds 18 3.3 Mechanical Properties and Crystallographic Analysis 21 3.3.1 Tensile Properties and Anisotropy 21 3.3.2 Crystallographic Texture and Grain Boundary Characteristics 23 3.3.3 Grain Size Distribution and Strenthening Mechanisms 25 3.3.4 Phase Constitution and Lattice Defect State 27 3.4 Summary of Results and Discussion 28 Chapter 4 Conclusions and Future Work 30 4.1 Conclusions 30 4.2 Contributions of This Study 31 4.3 Future Work 31 References 33

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