Abstract

Stainless steels with Fe/Cr/Ni ratios of 74/18/8, 71/17/12, and 55/20/25 were produced from elemental powders by high energy mechanical alloying at both room and cryogenic temperatures. The effect of mechanical alloying temperature on martensitic transformation, the reversion of deformation-induced martensite-to-austenite upon annealing, and the influence of cooling rate on the thermal stability of reversed austenite upon cooling to room temperature were investigated in detail by in-situ and ex-situ X-ray diffraction (XRD) experiments, transmission electron microscopy (TEM) and Thermo-Calc simulations. A relative comparison of stainless steels after room temperature mechanical alloying indicated that the low nickel-containing steel underwent an almost complete martensitic transformation. However, martensitic transformation by deformation through mechanical alloying at room temperature would not be possible with increasing nickel contents but was created partially at cryogenic temperature, the degree of which depended on the steel composition. The in-situ XRD studies exhibited that the deformation-induced martensite completely transformed to austenite at elevated temperatures. The complete reverse transformation temperature simulated by Thermo-Calc software was found to be lower than that of the experimentally determined ones. Additionally, the different cooling rates from the reversed austenite demonstrated that the slower cooling increased the thermal stability of reversed austenite at room temperature.

Graphic Abstract

中文翻译：

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成分，机械合金化温度和冷却速率对机械合金化不锈钢中马氏体相变及其回复的影响

摘要

Fe / Cr / Ni比为74/18 / 8、71 / 17/12和55/20/25的不锈钢是通过在室温和低温条件下通过高能机械合金化由元素粉末制成的。通过原位研究了机械合金化温度对马氏体相变，退火引起的形变马氏体向奥氏体的回复以及冷却速率对反向奥氏体热稳定性的影响。以及异位X射线衍射（XRD）实验，透射电子显微镜（TEM）和Thermo-Calc模拟。室温机械合金化后不锈钢的相对比较表明，低含镍钢经历了几乎完全的马氏体转变。然而，随着镍含量的增加，通过机械合金化在室温下通过变形产生的马氏体相变是不可能的，而是部分在低温下产生的，其程度取决于钢的成分。X射线原位研究表明，变形引起的马氏体在高温下完全转变为奥氏体。发现通过Thermo-Calc软件模拟的完全反向转化温度低于实验确定的温度。另外，与反向奥氏体不同的冷却速率表明，较慢的冷却提高了反向奥氏体在室温下的热稳定性。

图形摘要