Abstract

Nanocrystalline Fe–Cr alloys synthesized from pure components in a planetary ball mill with a chromium content of 20–48 at % were annealed for 4 h at temperatures of T_an = 400–700°C. Short-range order (SRO) evolution and phase separation dependent on T_an were studied using Mössbauer spectroscopy and X-ray diffraction. The precipitation of the σ-FeCr phase was observed only in the samples with 48 at % of Cr at T_an = 600 and 700°C. For all the samples, the grain growth began most intensively from 400°C, and the higher the Cr content in an alloy, the smaller the final size of grains after T_an = 700°C. The analysis of behavior of the mean hyperfine field on Fe nuclei and distribution of the hyperfine field width depending on T_an, as well as fitting of Mössbauer spectra with spectral components corresponding to the α (Cr depleted) and α' (Cr rich) phases, demonstrated that the mechanically alloyed Fe-Cr samples were characterized by weak short-range separation passing at T_an = 400°C to a nearly statistically uniform distribution of atoms. Heterogeneous short-range order with the α and α' regions was formed in the alloys with 30 at % of Cr and more after annealing at 500–700°C. An analysis with the material balance equation led to our conclusion about the existence of the grain boundary segregations of Cr atoms.

中文翻译：

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退火过程中纳米晶机械活化铁铬合金的短程有序演化

摘要

在行星球磨机中由纯成分合成的铬含量为20-48 at％的纳米晶Fe-Cr合金在T _an = 400-700°C的温度下退火4小时。使用Mössbauer光谱学和X射线衍射研究了取决于T _an的短程有序（SRO）演化和相分离。σ-FeCr相的沉淀仅在T _an  = 600和700°C时具有48 at％Cr的样品中观察到。对于所有样品，从400°C开始晶粒生长最密集，并且合金中Cr含量越高，在T _an之后晶粒的最终尺寸越小= 700°C。分析Fe核上的平均超精细场的行为以及取决于T _an的超精细场宽分布，以及将Mössbauer光谱与对应于α（贫Cr）和α'（富Cr）相的光谱分量进行拟合证明了机械合金化的Fe-Cr样品的特征是在T _an = 400°C时达到近乎统计上均匀的原子分布的弱短程分离。在500–700°C退火后，具有30at％Cr和更多Cr的合金中形成了具有α和α'区的异质短程有序。通过材料平衡方程的分析得出关于Cr原子晶界偏析的存在的结论。