发表机构
National Institute of Technology Jamshedpur（贾姆谢德布尔国家技术学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过MD/MC模拟发现，纳米晶Fe-18Cr-12Ni中晶界偏析（Ni贫化、Cr富集）延迟塑性流动起始，提高峰值应力，其作用主要发生在早期塑性流动阶段。
AI 中文摘要
奥氏体Fe-Cr-Ni合金中的晶界（GB）偏析主要在辐照或敏化材料中研究，在纳米晶状态下很少研究。采用混合分子动力学/蒙特卡洛（MD/MC）模拟来偏析三个独立的纳米晶Fe-18Cr-12Ni多晶体，并与相同微观结构上的退火和随机对照进行比较。Ni在晶界平面处贫化，而Cr在相邻原子壳层中富集；这两个方向在生产采样预算下均已确立，并且当三个微观结构之一被进一步采样时，它们会增强。Cr富集仅相对于远场晶粒内部得以分辨；常见的面心立方（fcc）和非fcc原子划分将富集壳层置于其自身的参考系中。在300 K下施加4.6 GPa的恒定单轴应力时，偏析多晶体达到50%应变所需时间比随机多晶体长约16%；与退火对照相比，晶界化学贡献了该增益的约三分之二，其余来自晶界弛豫。差异源于塑性流动早期的较低应变速率，而位错含量没有可分辨的变化。在固定应变速率下，偏析状态在300、750和950 K下的峰值应力比其退火对照高6-7%，并且在施加应力与流动应力匹配比率下，增益在所有三个温度下相同，仅随该比率升高而降低。因此，早期塑性流动是晶界化学起作用的阶段，而纳米晶体中模拟的晶界组成强烈依赖于参考区域。
英文摘要
Grain-boundary (GB) segregation in austenitic Fe-Cr-Ni alloys has been studied mainly in irradiated or sensitised material, rarely in the nanocrystalline state. Hybrid molecular dynamics/Monte Carlo (MD/MC) simulations are used to segregate three independent nanocrystalline Fe-18Cr-12Ni polycrystals, which are compared with annealed and random controls on the same microstructures. Ni is depleted at the GB plane and Cr is enriched in the adjacent atomic shell; both directions are established at the production sampling budget and strengthen when one of the three microstructures is sampled further. The Cr enrichment is resolved only against the far-field grain interior; the common partition into face-centred-cubic (fcc) and non-fcc atoms places the enriched shell in its own reference. Under a constant uniaxial stress of 4.6 GPa at 300 K, the segregated polycrystals take about 16% longer than random ones to reach 50% strain; measured against annealed controls, boundary chemistry contributes about two-thirds of this gain and boundary relaxation the rest. The difference arises from a lower strain rate early in plastic flow, with no resolvable change in dislocation content. At a fixed strain rate the segregated state has a 6-7% higher peak stress than its annealed control at 300, 750 and 950 K, and at matched ratios of applied to flow stress the gain is the same at all three temperatures, decreasing only as that ratio rises. Early plastic flow is thus the stage at which GB chemistry acts, and simulated GB composition in nanocrystals depends strongly on the reference region.
Comments20 pages, 9 figures, 5 tables; Supplementary Material (10 pages) as ancillary file. Data and code: https://doi.org/10.5281/zenodo.23189101
