Abstract Laser metal deposition (LMD) is an advanced manufacturing technology combining rapid prototyping and laser cladding technology, which has been applied to manufacture high performance parts with complex structure. In this study, Inconel-steel functionally graded materials (FGMs) with composition transitioning from 100 % 316 L incrementally graded to 100 % Inconel718 by different composition gradients (5%, 10 %, 20 %) were fabricated by LMD. The microstructure, phase evolution and mechanical properties of the components with different composition gradients (5%, 10 % and 20 %) were characterized by microscopy, energy dispersive spectroscopy, X-ray diffraction, micro-indentation and tensile tests. Brittle Laves phase could be observed when the content of Inconel718 exceeded 40 %. With the composition gradient decreasing, the range of micro-hardness along the deposition direction enlarged. The FGM micro-hardness had the widest range of 173 HV-308 HV when composition gradient was 5%. Fe and Ni, the main elements of alloys used in this study, transitioned linearly along the gradient direction and diffused fully between layers. By linearly fitting Fe content, the effect of composition gradient on element transition was determined. The presence of Laves phase was the main inducement leading to the micro-porous aggregation fracture. The best tensile properties with the highest tensile strength (527.05 MPa) and the highest elongation (26.21 %) were obtained by the FGM with composition gradient of 10 %. The findings will be helpful to choose appropriate gradient variation and understand the forming mechanism of functionally graded materials fabricated by laser additive manufacturing.

中文翻译：

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成分梯度变化对激光增材制造316L/Inconel718功能梯度材料微观结构和力学性能的影响

摘要 激光金属沉积（LMD）是一种结合快速成型和激光熔覆技术的先进制造技术，已应用于制造复杂结构的高性能零件。在这项研究中，通过不同的成分梯度（5%、10%、20%），成分从 100% 316 L 逐渐渐变到 100% Inconel718 的 Inconel-钢功能梯度材料 (FGM) 是通过 LMD 制造的。通过显微镜、能量色散谱、X射线衍射、显微压痕和拉伸试验对具有不同成分梯度（5%、10%和20%）的部件的微观结构、相演变和机械性能进行了表征。当 Inconel718 的含量超过 40% 时，可以观察到脆性 Laves 相。随着成分梯度的减小，沿沉积方向的显微硬度范围扩大。当成分梯度为5%时，FGM显微硬度范围最广，为173 HV-308 HV。本研究中使用的合金的主要元素 Fe 和 Ni 沿梯度方向线性过渡并在层间充分扩散。通过线性拟合Fe含量，确定了成分梯度对元素转变的影响。Laves 相的存在是导致微孔聚集断裂的主要诱因。具有最高拉伸强度 (527.05 MPa) 和最高伸长率 (26.21%) 的最佳拉伸性能是通过 FGM 获得的，成分梯度为 10%。