Ceramics-based additive manufacturing is a complex process and the solidification mechanism and microstructural evolution are currently not fully understood. In this work, AlO single tracks were formed using a customised selective laser melting (SLM) system equipped with a high power diode laser. The effects of laser energy density (LED) on geometry, microstructure and micro-mechanical properties of AlO tracks were investigated. To better understand the solidification mechanism, a transient three-dimensional thermal model was developed for predicting the thermal behaviour of the melt pool. The results indicated the use of high LED gave rise to decreased viscosity and surface tension of the molten alumina and led to localized melting of the substrate. Both, in turn, enabled the formation of a continuous solidified track. The solidified tracks were primarily composed of columnar dendrite. When relatively high LED (≥ 25.7 kJ/m) was applied, equiaxed dendrite appeared along the central line near the track surface. The size of dendritic grains decreased with the decreased LED, attributed to the increased cooling rate at solidification interface. The micro-hardness of the solidified track was found to be inversely proportional to the grain size owning to grain boundary strengthening effect.

中文翻译：

---

氧化铝的选择性激光熔化：单轨研究

基于陶瓷的增材制造是一个复杂的过程，目前尚未完全了解凝固机制和微观结构演变。在这项工作中，Al2O 单轨是使用配备高功率二极管激光器的定制选择性激光熔化 (SLM) 系统形成的。研究了激光能量密度 (LED) 对 Al2O3 轨道几何形状、微观结构和微机械性能的影响。为了更好地理解凝固机制，开发了一个瞬态三维热模型来预测熔池的热行为。结果表明，使用高 LED 会降低熔融氧化铝的粘度和表面张力，并导致基板局部熔化。反过来，两者都能够形成连续的固化轨迹。固化轨迹主要由柱状枝晶组成。当应用相对较高的 LED (≥ 25.7 kJ/m) 时，等轴枝晶出现在轨道表面附近的中心线上。树枝状晶粒的尺寸随着 LED 的减小而减小，这归因于凝固界面处冷却速度的增加。由于晶界强化效应，固化轨迹的显微硬度与晶粒尺寸成反比。