本論文以分子動力學模擬方法探討奈米級銅金屬粉末在不同粒徑尺寸、幾何形狀、排列方式與加熱速率之條件下，應用於金屬雷射粉體熔化成型積層製造(3D列印)技術之物理特性做比較與分析。本文選取三種不同形貌奈米級銅金屬粉進行研究，分別為實心圓球、空心圓球以及實心橢球，圓球形的奈米級粉末粒徑直徑分為12a、18a、24a，實心與空心各有六種不同排列組合；橢球形則分為平行型、歪斜型、端對邊型、端對端型四種，經過排列後產生二十四種組合。在三種不同加熱速率下藉由頸寬、迴轉半徑、勢能以及均方根位移等輔助條件之分析，探討在奈米尺度下銅金屬粉末在雷射燒結過程中的物理特性之變化情況。本文發現，奈米尺度下的奈米級銅金屬粉末無論是實心、空心或橢球，於室溫環境中皆會有自發產生固態燒結之現象。在雷射燒結過程中，銅的聚結溫度與熔化溫度都會隨著粒徑或原子數的減少而降低；而加熱速率越快，則會使銅的聚結溫度與熔化溫度隨之提升。橢球形銅粉末無論是在熱平衡或是雷射燒結階段，均以平行型的頸寬最大，而端對端型的頸寬最小。在奈米尺度下銅的熔化溫度比巨觀尺度下的熔點(1357.77K)還低。由本文可發現，除了奈米級金屬粉末的粒徑和加熱速率會影響3D列印材料的物理性質以外，幾何形狀和排列方式也是重要的影響因素。 In this present study, the molecular dynamics investigations on solid and hollow spherical copper nanoscale powders during the laser powder bed fusion additive manufacturing (3D printing) process are exhibited under different powder sizes and heating rates. The sizes of copper powders are varied from 12a, 18a and 24a, respectively. The six combinations of both solid and hollow spherical two-powder-model are chosen, respectively. The common neighbor analysis, neck width, mean square displacement, and gyration radius are utilized to investigate the nanoscale physical properties, which are coalescence and melting temperature, of copper powders under laser sintering process. Whatever solid or hollow spherical copper powders, we found that the solid-state sintering automatically takes place at room temperature. Moreover, except that the powder size and the heating rate of metal powder significantly affect the physical properties, the result of this study also shows that the geometry of the nanoscale powders is also an important role in the 3D printing process.
