Harwarth Michael, Brauer Adam, Huang Qiuliang, Pourabdoli Mehdi, Mola Javad
Materials Design and Structural Integrity Laboratory, Faculty of Engineering and Computer Sciences, Osnabrück University of Applied Sciences, 49076 Osnabrück, Germany.
Institute of Iron and Steel Technology, Technische Universität Bergakademie Freiberg, 09599 Freiberg, Germany.
Materials (Basel). 2021 Sep 4;14(17):5063. doi: 10.3390/ma14175063.
The influence of carbon on the phase transformation behavior of stainless steels with the base chemical composition Fe-13Cr (wt.%), and carbon concentrations in the range of 0-0.7 wt.%, was studied at temperatures between -196 °C and liquidus temperature. Based on differential scanning calorimetry (DSC) measurements, the solidification mode changed from ferritic to ferritic-austenitic as the carbon concentration increased. The DSC results were in fair agreement with the thermodynamic equilibrium calculation results. In contrast to alloys containing nearly 0% C and 0.1% C, alloys containing 0.2-0.7% C exhibited a fully austenitic phase stability range without delta ferrite at high temperatures. Quenching to room temperature (RT) after heat treatment in the austenite range resulted in the partial transformation to martensite. Due to the decrease in the martensite start temperature, the fraction of retained austenite increased with the carbon concentration. The austenite fraction was reduced by cooling to -196 °C. The variation in hardness with carbon concentration for as-quenched steels with martensitic-austenitic microstructures indicated a maximum at intermediate carbon concentrations. Given the steady increase in the tetragonality of martensite at higher carbon concentrations, as confirmed by X-ray diffraction measurements, the variation in hardness with carbon concentration is governed by the amount and stability of austenite.
研究了碳对基础化学成分Fe-13Cr（重量%）且碳浓度范围为0-0.7重量%的不锈钢在-196°C至液相线温度之间的相变行为的影响。基于差示扫描量热法（DSC）测量，随着碳浓度的增加，凝固模式从铁素体转变为铁素体-奥氏体。DSC结果与热力学平衡计算结果相当吻合。与含碳量接近0%和0.1%的合金相比，含碳量为0.2-0.7%的合金在高温下表现出完全奥氏体相稳定性范围且无δ铁素体。在奥氏体范围内进行热处理后淬火至室温（RT）会导致部分转变为马氏体。由于马氏体开始温度降低，残余奥氏体的比例随碳浓度增加。通过冷却至-196°C可降低奥氏体比例。具有马氏体-奥氏体微观结构的淬火钢的硬度随碳浓度的变化表明在中间碳浓度处出现最大值。如X射线衍射测量所证实，在较高碳浓度下马氏体的四方度稳步增加，硬度随碳浓度的变化受奥氏体的量和稳定性支配。
