中文摘要：

为了研究镍基合金焊材FM-52M的高温失延裂纹（DDC）,采用改进的应变-裂纹（STF）实验方法,提出新的裂纹敏感性判据——晶界滑移量。并将之与裂纹数量相结合定量评估不同温度、不同变形量条件下材料的DDC敏感性。结果表明：本研究中所得到的材料临界变形量6%大于传统STF方法得到的4%的临界变形量。预热处理、峰值温度、变形速率等条件都能显著影响DDC的敏感性。此外,利用显微硬度标记了许多微区,并对实验前后的微区进行了SEM观察,探讨晶界滑移与析出物在DDC的萌生与扩展过程中的作用。

英文摘要：

According to the improved strain-to-fracture test （STF） method, the value of grain boundary sliding was used as a new criterion to evaluate the susceptibility of ductility-dip cracking （DDC） in Ni-based alloy filler metal 52M（FM-52M） under various temperature and deformation conditions. The results show that the threshold strain of the test is 6%, which is larger than 4% obtained by previous STF method. Heat pretreatment, peak temperature, strain rate all have a great influence on the DDC susceptibility. Microhardness was used to mark interested micro-regions, from which SEM images were made before and after the test in order to explain the roles of grain boundary sliding and precipitates in DDC.