Laser powder bed fusion of Ti-6Al-4V parts: Thermal modeling and mechanical implications
Laser powder bed fusion of Ti-6Al-4V parts: Thermal modeling and mechanical implications
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DOI：
10.1016/j.ijmachtools.2017.04.007
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发表时间：
2017-08-01
影响因子：
14
通讯作者：
Shamsaei, Nima
中科院分区：
文献类型：
--
作者：
Masoomi, Mohammad;Thompson, Scott M.;Shamsaei, Nima
开发了一种连续尺度建模方法，并与三维有限元分析（FEA）一起使用，用于模拟尺寸为10x5x0.06 mm（3）的Ti-6Al-4V双层平行六面体在激光粉末床融合（L-PBF）（一种金属增材制造（AM）方法）过程中的温度响应。该模型已被验证，使用实验熔池测量从文献中，也占熔化潜热和有效的，温度依赖性的传输特性。离散化的温度，温度时间变化率（即冷却速率）和温度梯度进行了研究的各种扫描策略和激光器的数量，即1，2或4。研究了多激光PBF（ML-PBF）固有的热响应。专用于单个激光器或“岛”的粉末床的子区域区域的数量是不同的。平均，最大冷却速率和每层的温度梯度，以及空间的标准偏差，或均匀性，这些指标，提出和Ti-6Al-4V的微观结构特征和力学特性的影响进行了讨论。结果表明，增加激光器的数量将减少生产时间，以及局部冷却速率和残余应力的大小;然而，残余应力场和微观结构的各向异性可能会增加基于所采用的扫描策略。在一般情况下，扫描策略，采用减少轨道长度平行于部分的最短的边缘，与岛“堆叠”在一个单位行，被证明是最有益的L-PBF。
A continuum-scale modeling approach is developed and employed with three-dimensional finite element analysis (FEA), for simulating the temperature response of a Ti-6Al-4V, two-layered parallelepiped with dimensions of 10x5x0.06 mm(3) during Laser Powder Bed Fusion (L-PBF), a metals additive manufacturing (AM) method. The model has been validated using experimental melt pool measurements from the literature and also accounts for latent heat of fusion and effective, temperature-dependent transport properties. The discretized temperature, temperature time rate of change (i.e. cooling rate) and temperature gradient are investigated for various scan strategies and number of lasers, i.e. 1, 2 or 4. The thermal response inherent to multi-laser PBF (ML-PBF) is investigated. The number of sub-regional areas of the powder bed dedicated to individual lasers, or 'islands', was varied. The average, maximum cooling rate and temperature gradient per layer, as well as the spatial standard deviation, or uniformity, of such metrics, are presented and their implications on microstructure characteristics and mechanical traits of Ti-6Al-4V are discussed. Results demonstrate that increasing the number of lasers will reduce production times, as well as local cooling rates and residual stress magnitudes; however, the anisotropy of the residual stress field and microstructure may increase based on the scan strategy employed. In general, scan strategies that employ reduced track lengths oriented parallel to the part's shortest edge, with islands 'stacked' in a unit-row, proved to be most beneficial for L-PBF.