本研究基於金屬積層製造元件中，微觀結構與力學性質在不同方向常呈現各向異性之現象，提出此差異可能與製程過程中沿 Z 軸（垂直堆疊方向）及 X 軸（水平掃描方向）之熱行為差異相關，因此，本研究以自主開發之雷射金屬箔材積層製造（Laser Foil Printing, LFP）系統進行 Inconel 625 金屬元件製備，並建立三維有限元素熱傳模型模擬加工過程中的動態熱場變化，為確認模型之可靠性，本研究首先比較模擬與實驗所得之熔池幾何尺寸，結果顯示熔池尺寸預測結果與實驗量測結果具有合理一致性，證實所建立之熱模型能有效描述 LFP 製程中的熱傳遞行為，基於驗證後之模型，進一步分析不同觀測平面之溫度梯度隨時間演變、熱通量分布及不同方向之凝固冷卻速率。結果顯示，XY 與 YZ 平面之最大溫度梯度相對大小會隨熱循環時間改變，呈現明顯之暫態熱場特性；熱通量向量則顯示熱量由高溫區向周圍及下方材料傳遞。此外，X 軸與 Z 軸方向之凝固冷卻速率分別為 2.06×10^5 K/s 與 1.95×10^5 K/s，為探討熱行為差異對微觀結構之影響，本研究利用 EBSD、XRD 及 SEM 進行微觀組織分析，結果顯示，LFP 製備之 Inconel 625 在 YZ 平面呈現沿 Z 軸方向生長之柱狀晶結構，顯示其具有明顯的微觀組織各向異性，此與模擬所得之暫態溫度梯度分布及局部熱傳方向相互對應，說明方向性熱傳導對晶粒成長行為具有重要影響，最後，透過拉伸試驗進一步評估微觀組織差異對機械性質之影響，結果顯示 Z 軸試片與 X 軸試片在延展性上具有約24.3% 的差異，證實 LFP 製程中方向性熱傳行為為影響微觀組織演變與力學各向異性之重要因素之一，本研究建立了熱傳模擬、微觀組織分析與機械性質之間的關聯，提供金屬積層製造中熱行為對材料特性影響之物理機制參考。

Anisotropic microstructures and mechanical properties are commonly observed in metal additively manufactured components. In this study, it is proposed that such anisotropic behavior is associated with differences in thermal behavior along the Z-axis (vertical building direction) and X-axis (horizontal scanning direction) during the manufacturing process. Therefore, an in-house developed Laser Foil Printing (LFP) system was utilized to fabricate Inconel 625 components, and a three-dimensional finite element heat transfer model was established to simulate the transient thermal field evolution during the fabrication process. To validate the reliability of the numerical model, the simulated melt pool geometry was first compared with experimental measurements. The results showed that the predicted melt pool dimensions were in reasonable agreement with the experimental results, confirming that the established thermal model could effectively describe the heat transfer behavior during the LFP process. Based on the validated model, the transient temperature-gradient evolution, conductive heat-flux distribution, and solidification cooling behavior were further analyzed. The relative maximum temperature gradients on the XY and YZ planes varied with time, demonstrating the transient nature of the directional thermal field. The conductive heat-flux vectors further revealed heat dissipation from the high-temperature region toward the surrounding and underlying material. The calculated solidification cooling rates along the X- and Z-directions were 2.06×10^5 K/s and 1.95×10^5 K/s, respectively.
To investigate the influence of thermal behavior on microstructural evolution, electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses were performed. The results showed that the LFP-fabricated Inconel 625 exhibited columnar grain structures growing along the Z-axis direction on the YZ plane, indicating significant microstructural anisotropy. This observation was consistent with the transient thermal-gradient distribution and local heat-flow characteristics obtained from the simulation, suggesting that directional thermal history plays an important role in grain-growth behavior. Finally, tensile tests were conducted to further evaluate the effect of microstructural differences on mechanical properties. The results showed an approximately 24.3% difference in ductility between the Z-axis and X-axis specimens, demonstrating that directional thermal behavior during the LFP process is one of the key factors influencing microstructural evolution and the resulting anisotropic mechanical properties. This study establishes the relationship among thermal simulation, microstructural characterization, and mechanical properties, providing insight into the influence of thermal behavior on material characteristics in metal additive manufacturing.

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