Elemental segregation to lattice defects in the CrMnFeCoNi high-entropy alloy during high temperature exposures
Elemental segregation to lattice defects in the CrMnFeCoNi high-entropy alloy during high temperature exposures
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DOI：
10.1016/j.actamat.2021.116719
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发表时间：
2021-02-23
期刊：
影响因子：
9.4
通讯作者：
Dlouhy, Antonin
中科院分区：
文献类型：
--
作者：
Heczko, Milan;Mazanova, Veronika;Dlouhy, Antonin
研究了小塑性预应变对等原子CrMnFeCoNi FCC固溶体高温稳定性和显微组织的影响。特别注意的是，是否有任何合金元素偏析到个别位错。为此，CrMnFeCoNi样品首先在室温下拉伸变形至0.2%和2.3%的塑性应变，随后在973 K下退火800小时。预应变激活了{111}型滑移面上1/2型位错的滑移。这种平面滑移与特殊的Sigma 3晶界的相互作用形成了大量的位错段，具有适合于HR-STEM中位错核心的可靠端部分析的-型晶体学取向。1/2位错的核心被推到对所研究的晶界被发现是接近紧凑的配置。在Super-X EDS绘图的灵敏度范围内，在位错附近没有检测到浓度梯度，这表明在预变形和退火后合金的任何元素成分在位错核处富集。然而，富铬的tetra-sigma相成核和生长在晶界三重结在此退火过程中，该过程没有加速增强的位错密度后存在的预应变。在晶界附近的Cr贫化区中观察到明显的铬梯度，这表明Cr运输通过从本体到晶界的相对缓慢的扩散，然后通过相对快速的扩散沿着晶界到沉淀物而发生。伴随着晶界附近的Cr耗尽是同时的Ni和Mn富集，这促进了长时间退火后在晶界上观察到的L1（0）NiMn相的形成。(C)2021由Elsevier Ltd代表Acta Materialia Inc.发布。
The influence of small plastic pre-strains on the elevated-temperature stability and microstructure of the equiatomic CrMnFeCoNi FCC solid solution is investigated. Particular attention is given to whether any of the alloy elements segregate to individual dislocations. To that end, CrMnFeCoNi samples were first deformed in tension at room temperature to plastic strains of 0.2 and 2.3%, and subsequently annealed at 973 K for 800 hours. The pre-strains activated planar slip of 1/2-type dislocations on {111}-type glide planes. Interactions of this planar slip with special Sigma 3 grain boundaries formed a large number of dislocation segments with a -type crystallographic orientation suitable for a credible end-on analysis of dislocation cores in HR-STEM. The cores of the 1/2 dislocations pushed up against the investigated grain boundaries were found to be close to the compact configuration. Within the sensitivity of the Super-X EDS mapping, no concentration gradient was detected near dislocations that would indicate enrichment at dislocation cores of any of the elemental constituents of the alloy after the pre-deformation and annealing. However, a Cr-rich tetragonal sigma phase nucleated and grew at grain boundary triple junctions during this anneal, processes that were not accelerated by the enhanced dislocation density present after pre-strain. A clear chromium gradient was observed in the Cr-depleted zones near grain boundaries suggesting that Cr transport occurred by relatively slow diffusion from the bulk to the grain boundaries and then by relatively fast diffusion along the grain boundaries to the precipitates. Accompanying the Cr depletion near grain boundaries is a simultaneous Ni and Mn enrichment, which promotes formation of the L1(0) NiMn phase that is observed on the grain boundaries after prolonged annealing. (C) 2021 Published by Elsevier Ltd on behalf of Acta Materialia Inc.