The phase transformation of HP40Nb alloy at various temperatures and times was investigated and the microstructural evolution in aging process was characterised. Additionally, the mechanical tests were implemented for aged specimens. Experimental results indicate the microstructure of as-cast alloy consists of the austenite matrix with skeletal-shaped primary carbides. NbC carbide changes into G phase from 700 °C to 990 °C, and the nose temperature of transformation ranges from 900 °C to 950 °C. M₇C₃ carbide tends to transform into M₂₃C₆ carbide at higher temperature. Meanwhile, numerous secondary carbides are precipitated in the initial aging stage and dissolves gradually in further process. The interdendritic precipitates coalesce and coarsen continuously in aging treatment. The tensile strengths and the micro-hardness increase slightly followed by the continuous reduction in exposure, while the elongation and impact toughness decrease continuously. The microstructural evolution during aging process is consistent with the variation of mechanical properties.

研究了HP40Nb合金在不同温度，不同时间的相变，表征了时效过程中的组织演变。此外，还对老化的试样进行了机械测试。实验结果表明，铸态合金的组织由奥氏体基体和骨架状的初生碳化物组成。NbC碳化物从700°C到990°C转变为G相，转变的鼻端温度在900°C到950°C范围内。M ₇ C ₃碳化物趋于转变成M ₂₃ C ₆高温下碳化。同时，大量的二次碳化物在初始时效阶段析出并在进一步的过程中逐渐溶解。在时效处理中，枝晶间的沉淀物会聚结并不断粗化。拉伸强度和显微硬度略有增加，随后暴露量不断降低，而伸长率和冲击韧性则不断降低。时效过程中的微观结构演变与力学性能的变化是一致的。