隨著機械加工成品的要求提高，傳統鑄造加工受限於技術瓶頸，許多研究開始投入到金屬積層製造中，其中DED加工技術即是目前較普遍的一種，然而DED加工技術擁有相當大量的製程參數，且加工過程涉及到複雜的固力與熱流現象，所以為了取得DED加工過程的溫度場，本研究利用數值模擬軟體ANSYS Fluent建立三維暫態的兩軌兩層DED加工數值模型，模型所使用的材料為Inconel 718並使用動網格方法中的鋪層法(Layering)來模擬金屬沉積物堆疊之情況，透過與實驗驗證，證明模型在預估金屬沉積物幾何外型及加工溫度場有一定的準確性。
研究結果顯示隨著雷射功率越大或雷射掃描速率越小，金屬沉積的範圍及沉積物高度將越大；在微結構方面，G/R值視為判定微結構型態的固化參數，由結果顯示當雷射功率較小時，單一金屬沉積物內部之G/R值差異越小，因此結構較一致；透過優化分析可得當光斑半徑為1.5 mm、重疊率為26.2%且雷射功率為1000 W、雷射掃描速率為6 mm/s具有較佳的加工效率及較高且穩定的G/R值；在製程的改善方面，基板預熱有助於增加金屬沉積物的幾何尺寸，但是隨著預熱溫度越高，金屬沉積物內部G/R值將大幅下降，容易生成等軸晶；另外，縮短加工停滯時間及使用多向掃描加工，將有助於提升加工的效率，且對於金屬沉積物內部之微結構並無明顯的影響；而逐層調降雷射功率則能有效改善多層加工的成品微結構。

Because of the increase in manufacturing demands, many studies began to focus on additive manufacturing. DED is one of the common processing technology. However, DED has a large number of processing parameters and involves the complicated phenomenon of the solid mechanic and heat flow. In order to obtain the temperature field of DED, the study uses Ansys Fluent software to establish a three-dimensional numerical model on two-track and two-layer scanning in DED, and the dynamic mesh model is used to approximate the situation of metal deposition. Through the experimental verification, it is proved that the model has certain accuracy in predicting the geometry of metal deposition and the processing temperature field.
The research results show that as the laser power increases or the laser scanning speed decreases, the width and height of metal deposition will increase. In the aspect of microstructure, the temperature gradient (G) and solidification rate (R) are the two main parameters that affect the deposited microstructure. The G/R ratio governs the solidification mode while the cooling rate controls the scale of the deposited microstructure. When the laser power decreases, the difference of the G/R ratio in a deposition at different locations will decrease, so the microstructure will become more consistent. Through analysis of optimization, it is found that the laser spot radius of 1.5 mm, the overlapping ratio of 26.2%, the laser power of 1000 W, and the scanning speed of 6mm/s have better processing efficiency and higher G/R ratio. In the aspect of process improvement, substrate preheating can effectively increase the morphology of deposition, but the high preheating temperature leads to a low G/R ratio in the deposition, and it will produce the equiaxed dendritic easily. Moreover, reducing idle time and using double-sided scanning have little influence on microstructure, but they are beneficial to improve the processing efficiency. Layer-by-layer reduction of laser power makes the microstructure more consistent in the multi-layer scanning process.

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