| 摘要: | 本文為藉由分子動力學模擬方法，探討鋁金屬奈米粉末應用於雷射粉體熔化成型積層製造(3D列印)之研究。選取三種不同幾何形貌的鋁金屬奈米粉末進行研究，分別為實心圓球、空心圓球及實心橢球。不同粉末粒徑之實心與空心圓球狀鋁金屬奈米粉末各三種，並各分別組合成六種情況；平行型、歪斜型、端對邊型、端對端型的四種實心橢球的排列，也組合成十二種情況。用三種不同的加熱速率，觀察鋁金屬奈米粉末組合對在室溫環境下，以及高溫雷射燒結之過程中，在奈米尺度下鋁金屬粉末之聚結溫度、熔化溫度等物理性質的探討。經由頸寬、勢能、迴轉半徑等輔助條件之分析，發現無論是實心圓球、空心圓球或實心橢球之鋁金屬奈米粉末，在室溫環境下皆會發生自體燒結的現象。此外，在高溫雷射燒結之過程中，在固定的粒徑之下，加熱速率越快速會驅使鋁金屬奈米粉末的聚結/熔化溫度提升，在固定的加熱速率之下，會隨著粉末粒徑之縮小或是粉末原子數之減少，鋁金屬奈米粉末的聚結/熔化溫度也會隨之降低。實心橢球在熱平衡或是高溫雷射燒結階段的頸寬數據，以平行型的實心橢球狀鋁金屬奈米粉末的頸寬值最大，而端對端型的頸寬值最小。研究結果顯示，在奈米尺度下鋁金屬的熔化溫度比巨觀尺度下的熔點明顯地下降，除了金屬粉末粒徑和加熱速率會顯著影響積層製造時的物理性質以外，奈米級金屬粉末的幾何形狀與形貌也是重要的影響因素。
A study of nanoscale aluminum powder applied on the laser powder bed fusion additive manufacturing process by the molecular dynamics simulation method performed. Three nanoscale aluminum powders with different geometric shape selected and utilized to explore the morphological effect. Morphology of aluminum powder includes solid sphere, hollow sphere, and solid ellipsoid. Various diameters of solid sphere powder made up to six study cases, and similar combinations applied to hollow sphere powder, as well. Moreover, four types of solid ellipsoidal powder, such as parallel, skew, end-to-side, and side-to-side was composed to twelve study cases. Heating rates were properly monitored and analyzed auxiliary conditions such as neck width, potential energy, and gyration radius to observe the coalescence and melting temperature of nanoscale aluminum in the room temperature environment or high-temperature laser sintering process. Results reviled the solid state sintering automatically took place at room temperature in case of solid spherical, hollow spherical, or solid ellipsoidal aluminum powder. In constant nanoscale size sintering process, the coalescence and melting temperature of nanoscale aluminum powder decreased with shrinking size or the reducing number of atoms. On the other hand, the coalescence and melting temperature of nanoscale aluminum rose with increasing the heating rate in the constant heating rate. In thermal equilibrium or high-temperature laser sintering process, the parallel type with a largest value of neck width, while that value of end-to-end type was the smallest for solid ellipsoidal aluminum powder. Outcome also demonstrated the size of powder dominated meting temperature; melting point of nanoscale aluminum is significantly lower than macroscopic aluminum. In this study, metallic powder particle size and heating rate obviously affect the physical properties of additive manufacturing, the geometries and morphologies of nanoscale metallic powder play another effective role to the process. |
