Formation of the Ni3Nb δ-Phase in Stress-Relieved Inconel 625 Produced via Laser Powder-Bed Fusion Additive Manufacturing
Formation of the Ni3Nb δ-Phase in Stress-Relieved Inconel 625 Produced via Laser Powder-Bed Fusion Additive Manufacturing
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DOI：
10.1007/s11661-017-4304-6
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发表时间：
2017-11-01
影响因子：
2.8
通讯作者：
Ng, Daniel S.
中科院分区：
文献类型：
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作者：
Lass, Eric A.;Stoudt, Mark R.;Ng, Daniel S.
研究了激光粉末床增材制造的Inconel 625在1143 K（870 ℃）下进行1小时的构建后应力消除退火期间的微观结构演变。据发现，这种工业推荐的热处理促进了正交D 0（a）Ni 3 Nb δ相的显著部分的形成。已知该相对常规锻造Inconel 625中的断裂韧性、延展性和其他机械性能具有有害影响;并且通常认为对材料的使用性能有害。发现三角形相片晶在铸态凝固组织的枝晶间区域内析出。由于在凝固过程中发生的微观偏析，这些区域富含溶质元素，特别是Nb和Mo。发现在1073 K（800 ℃）下δ相的沉淀需要长达4小时。这表明了一种潜在的替代应力消除处理窗口，其减轻了该合金中的δ相形成。最后，建议对增材制造的Inconel 625进行均匀化热处理，因为对δ相沉淀的敏感性增加，从而增加了材料性能在使用中显著退化的可能性。(C)矿物、金属和材料协会和ASM国际（美国以外）2017
The microstructural evolution of laser powder-bed additively manufactured Inconel 625 during a post-build stress-relief anneal of 1 hour at 1143 K (870 degrees C) is investigated. It is found that this industry-recommended heat treatment promotes the formation of a significant fraction of the orthorhombic D0(a) Ni3Nb delta-phase. This phase is known to have a deleterious influence on fracture toughness, ductility, and other mechanical properties in conventional, wrought Inconel 625; and is generally considered detrimental to materials' performance in service. The delta-phase platelets are found to precipitate within the inter-dendritic regions of the as-built solidification microstructure. These regions are enriched in solute elements, particularly Nb and Mo, due to the micro-segregation that occurs during solidification. The precipitation of delta-phase at 1073 K (800 degrees C) is found to require up to 4 hours. This indicates a potential alternative stress-relief processing window that mitigates delta-phase formation in this alloy. Ultimately, a homogenization heat treatment is recommended for additively manufactured Inconel 625 because the increased susceptibility to delta-phase precipitation increases the possibility for significant degradation of materials' properties in service. (C) The Minerals, Metals & Materials Society and ASM International (outside the USA) 2017