Abstract Functionally graded material has been increasingly attractive due to the locally designed and optimized material properties. In the present paper, to achieve high thermal lattice structural stability and high corrosion resistance in each side of one bulk material, an Fe3Ni–FeNi compositionally graded material (FGM) bulk sample has been fabricated using an innovative wire-arc additive manufacturing process. A subsequent homogenization post-production heat treatment is applied to stabilize the phase composition and eliminate the possible segregation in the as-fabricated sample. Meanwhile, the high intensity neutron diffraction instrument WOMBAT is conducted to measure the phase evolution processes in the bulk sample in-situ, thus the thermal induced lattice evolutions of Fe3Ni and FeNi can be accurately obtained dynamically in the function of time. According to the results, the WAAM has successfully fabricated the target FGM with uniform Ni content gradient. However, hot cracking defects are found in the bulk sample because of the inadequate interpass temperature setting. As analyzed from neutron diffraction results, the homogenization heat treatment has improved the phase thermal stability of the FGM and the application temperature of the Fe3Ni–FeNi FGM should be limited under 630 °C.

中文翻译：

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生产后热处理对 Fe3Ni-FeNi 功能梯度材料相演化的影响：原位中子衍射研究

摘要 由于局部设计和优化的材料特性，功能梯度材料越来越受到关注。在本文中，为了在一种大块材料的每一侧实现高热晶格结构稳定性和高耐腐蚀性，使用创新的线弧增材制造工艺制造了 Fe3Ni-FeNi 成分梯度材料 (FGM) 大块样品。随后的均质化生产后热处理用于稳定相组成并消除制造样品中可能的偏析。同时，高强度中子衍射仪WOMBAT进行原位测量大块样品中的相演化过程，因此可以准确地动态获得 Fe3Ni 和 FeNi 的热诱导晶格演化随时间的变化。根据结果​​，WAAM 成功地制造了具有均匀 Ni 含量梯度的目标 FGM。然而，由于层间温度设置不当，在大块样品中发现了热裂纹缺陷。从中子衍射结果分析，均质化热处理提高了 FGM 的相热稳定性，Fe3Ni-FeNi FGM 的应用温度应限制在 630 °C 以下。