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激光增材制造过程中微结构及其演化

激光增材制造历程中微布局及其演化与制造参数之间关联的谋略猜测,已成为基于增材制造的材料/布局设计和开拓历程的紧张组成部分。选区激光烧结(SLS)增材制造历程中,微布局演化极端依附于局部温度的急剧变更,故而老例的等温相场模型很难适用于SLS的模拟。

来自德国达姆施塔间谍业大年夜学的终生教授胥柏喷鼻引导的团队,与南京航空航天大年夜学的青年千人易敏教授相助,建立了一种热力学自洽的非等温相场模型,用以钻研SLS增材制造中微布局的演化。该模型斟酌微布局与热传导的强耦合,SLS局部极高温导致的局部熔化,以及激光-粉末互相感化。并提出了一种类似于求解最小着色数问题的新办理规划,结合晶粒追踪措施,该规划可仅用8个序参量来模拟具有多达200个晶粒的系统。本钻研还应用了基于LM算法的非线性优化措施,同时拟合模型与实验中外面能,晶界能随温度变更的趋势,以获取用于非恒温相场的模型参数。分外埠,将该非等温相场模型用于SLS处置惩罚316L不锈钢粉末的钻研,揭示了激光功率和扫描速率对孔隙率、外面描写、温度散播、晶粒几何外形以及致密度等微不雅布局特性的影响规律,并证明了该模型可用于猜测SLS历程中致密化因子与激光比能量之间的关联。该事情提出的非等温相场模型及其相关高效数值措施,有望用于SLS增材制造的大年夜规模谋略模拟。

该文颁发于npj Computational Materials 5: 81 (2019)。

3D non-isothermal phase-field simulation of microstructure evolution during selective laser sintering

Yangyiwei Yang, Olav Ragnvaldsen, Yang Bai, Min Yi & Bai-Xiang Xu

During selective laser sintering (SLS), the microstructure evolution and local temperature variation interact mutually. Application of conventional isothermal sintering model is thereby insufficient to describe SLS. In this work, we construct our model from entropy level, and derive the non-isothermal kinetics for order parameters along with the heat transfer equation coupled with microstructure evolution. Influences from partial melting and laser-powder interaction are also addressed. We then perform 3D finite element non-isothermal phase-field simulations of the SLS single scan. To confront the high computation cost, we propose a novel algorithm analogy to minimum coloring problem and manage to simulate a system of 200 grains with grain tracking algorithm using as low as 8 non-conserved order parameters. Specifically, applying the model to SLS of the stainless steel 316L powder, we identify the influences of laser power and scan speed on microstructural features, including the porosity, surface morphology, temperature profile, grain geometry, and densification. We further validate the first-order kinetics of the transient porosity during densification, and demonstrate the applicability of the developed model in predicting the linkage of densification factor to the specific energy input during SLS.

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