Thermal stability of retained austenite in 1C-1.5Cr steels with two Si and Mn contents is studied. Time-resolved high resolution synchrotron X-ray radiation and dilatometry are employed. The threshold transformation temperatures, decomposition kinetics, associated transformation strain, as well as the influence of Si and Mn were investigated. The coefficients of linear thermal expansion for both the bulk materials and individual phases are also obtained. The results indicate that an increase in the Mn and Si contents show little influence on the onset of retained austenite decomposition, but result in more thermally stable austenite. The decomposition is accompanied by a simultaneous increase in ferrite content which causes an expansive strain in the order of ${10}^{-4}$, and subsequent cementite development from 300 to 350 °C which causes a contraction that helps to neutralise the expansive strain. During decomposition, a continuous increase in the carbon content of austenite, and a reduction in that of the tempered-martensite/ferrite phase was observed. This process continued at elevated temperatures until full decomposition was reached, which could take less than an hour at a heating rate of $0.05°\mathrm{C}$/s. Additionally, the observation of austenite peak splitting on samples with high Mn and Si contents suggests the existence of austenite of different stabilities in such matrix.

研究了具有两种Si和Mn含量的1C-1.5Cr钢中残留奥氏体的热稳定性。使用时间分辨的高分辨率同步加速器X射线辐射和膨胀法。研究了阈值转变温度，分解动力学，相关的转变应变以及硅和锰的影响。还获得了散装材料和各个相的线性热膨胀系数。结果表明，Mn和Si含量的增加对残余奥氏体分解的开始几乎没有影响，但导致了热稳定性更高的奥氏体。分解伴随着铁素体含量的同时增加，从而导致膨胀应变约为${10}^{-4}$，随后渗碳体从300℃发展到350℃，引起收缩，这有助于抵消膨胀应变。在分解期间，观察到奥氏体的碳含量连续增加，并且回火马氏体/铁素体相的碳含量降低。此过程在升高的温度下继续进行，直到达到完全分解为止，在加热速率为200℃的情况下，此过程可能需要不到一个小时的时间。$0.05°\mathrm{C}$/ s。另外，在具有高Mn和Si含量的样品上观察到奥氏体峰分裂表明在这种基质中存在具有不同稳定性的奥氏体。