Abstract Vibrating sample magnetometry, VSM, was applied to follow the evolution of the austenite-to-martensite transformation in AISI D2 tool steel at cryogenic temperatures and to determine the associated changes in magnetic hardness. Data shows that the transformation can progress during cooling from room temperature (RT) to −193 °C and, more surprising, during re-heating from −193 °C to RT, indicating the formation of, so called, isothermal or thermally activated martensite. The thermally activated conversion of austenite into martensite occurred in the temperature range −33 °C ≤ T ≤ −173 °C and was fastest at −113 °C. Additionally, VSM revealed that the magnetic hardness decreases in correspondence with the formation of martensite. Data is interpreted in terms of continuous growth of the (ferromagnetic) martensite units at cryogenic temperatures that reduces the number of (paramagnetic) austenite regions retained in the material. Eventually, the work is put in perspective to arrive at an understanding of the effect of cryogenic treatment on the microstructure and performance of martensitic steels.

中文翻译：

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AISI D2 钢的低温处理：等温马氏体形成和“马氏体调节”的作用

摘要 振动样品磁力计 VSM 用于跟踪 AISI D2 工具钢在低温下奥氏体到马氏体转变的演变，并确定相关的磁硬度变化。数据显示，在从室温 (RT) 冷却到 -193 °C 的过程中，转变可以进行，更令人惊讶的是，在从 -193 °C 到 RT 的再加热过程中，转变可以进行，这表明形成了所谓的等温或热活化马氏体. 奥氏体到马氏体的热活化转化发生在 -33 °C ≤ T ≤ -173 °C 的温度范围内，在 -113 °C 时最快。此外，VSM 显示磁硬度随着马氏体的形成而降低。数据是根据（铁磁）马氏体单元在低温下的连续增长来解释的，这减少了材料中保留的（顺磁）奥氏体区域的数量。最终，这项工作被置于透视之中，以了解深冷处理对马氏体钢的微观结构和性能的影响。