Dai Donghua, Gu Dongdong, Poprawe Reinhart, Xia Mujian
College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; Institute of Additive Manufacturing (3D Printing), Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; Institute of Additive Manufacturing (3D Printing), Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
Sci Bull (Beijing). 2017 Jun 15;62(11):779-787. doi: 10.1016/j.scib.2017.05.007. Epub 2017 May 11.
A transient three dimensional model for describing the temperature behavior, thermo-capillary convection, microstructure evolution and the resultant mechanical properties during selective laser melting of AlN/AlSi10Mg composite is proposed. The powder-solid transformation, temperature dependent physical properties and the preservation of the heat are taken into account. The effect of the additive manufacturing multilayer feature on the molten pool dynamics, cooling rate, crystal size, microstructure morphology, micro-hardness and types of the residual stress has been investigated. It shows that the operating temperature and the thermo-capillary convection obtained within the molten pool generally increases as the processing multilayers are successively added, while the thermal effect depth is negatively reduced. The preferential direction of the heat diffusion generally changes from a downward pattern, then to the slightly strengthened horizontal direction and finally to a typically horizontal one for various deposited layers being processed. Therefore, the microstructure of the solidified part along the building direction (Region I to Region V) undergoes an interesting transformation: directional columnar cellular microstructure, crosswise-extended cellular microstructure, refined cellular microstructure, fragmentation microstructure and the coarse cellular microstructure. The tensile stress and the compressive stress are comprehensively obtained within the finally solidified layers, significantly influencing the micro-hardness.
提出了一种瞬态三维模型，用于描述AlN/AlSi10Mg复合材料选择性激光熔化过程中的温度行为、热毛细对流、微观结构演变以及由此产生的力学性能。该模型考虑了粉末-固体转变、随温度变化的物理性能以及热量的保留。研究了增材制造多层特征对熔池动力学、冷却速率、晶体尺寸、微观结构形态、显微硬度和残余应力类型的影响。结果表明，随着加工层数的依次增加，熔池内的工作温度和热毛细对流通常会升高，而热影响深度则呈负向减小。对于不同的沉积层，热扩散的优先方向通常从向下模式，然后变为略有增强的水平方向，最后变为典型的水平方向。因此，沿构建方向（从区域I到区域V）凝固部分的微观结构经历了有趣的转变：定向柱状胞状微观结构、横向扩展胞状微观结构、细化胞状微观结构、破碎微观结构和粗大胞状微观结构。在最终凝固层内综合获得了拉应力和压应力，这对显微硬度有显著影响。
