以S31042奥氏体耐热钢为研究对象，采用短时高温时效处理后在700℃下对其进行长期蠕变性能测试。通过OM、SEM和TEM等手段表征了S31042钢蠕变过程析出相的类型和演化规律，并利用蠕变实验分析了高温时效处理对S31042钢高温性能的影响。结果表明，经1050℃时效10 h处理后，S31042钢组织中析出大量尺寸在100 nm左右的Z相，降低了固溶态S31042钢中合金元素Cr和Nb的过饱和度，减小了M₂₃C₆相的形核驱动力，将蠕变过程晶界上析出M₂₃C₆相的形态由连续的链状调控为断续的短棒状。短棒状M₂₃C₆相的形成能够在不影响材料塑性的前提下，增大晶界滑动的阻力，改善材料的持久塑性。

S31042 steel is a typical 25Cr-20Ni-type austenitic heat-resistant steel with excellent oxidation and corrosion resistance, and its creep rupture strength can be improved by the addition of Nb and N. This austenitic steel is widely used in superheater and reheater in ultrasupercritical power plants. At high temperatures, its performance is associated with the formation and evolution of Z, MX, and M₂₃C₆ phases. Till date, few studies have addressed the precipitation behavior of the Z phase in austenitic steel and the reinforcing mechanism of different M₂₃C₆ phases remains unclear. To clarify this, the ageing treatment of S31042 steel was performed at 1050^oC, and the evolution behavior, thermal stability, and strengthening mechanism of the precipitates during creep tests were investigated. Furthermore, the relation between precipitate evolution and high-temperature performance was elucidated via OM, SEM, TEM, and creep tests. The supersaturation degree of the alloying components in solution-treated S31042 steel decreased after ageing at 1050^oC and the driving force for M₂₃C₆ phase formation became smaller, resulting in a discontinuous distribution of the rod-like M₂₃C₆ phase along the austenite grain boundaries during the creep tests. At high stress levels, this discontinuous distribution of the rod-like M₂₃C₆ phase along the austenite grain boundaries increased the resistance to grain boundary sliding without changing the ductility, thus improving the rupture ductility of the steel. At low stress levels, the strengthening effects of the M₂₃C₆ phase discontinuously distributed along the austenite grain boundaries in aged steel were not as strong as those in solution-treated steel.