中文摘要：

为研究M/A岛对T24钢焊接接头不完全淬火区（ICHAZ）冲击性能的影响,本文对T24钢在580,900和950℃下进行亚温正火,采用扫描电镜、透射电镜、维氏硬度、冲击试验等方法对T24钢ICHAZ的组织和冲击性能进行了研究。结果表明：经不同温度亚温正火的T24钢ICHAZ晶界均分布有硬脆相M/A岛;随着正火温度的升高,ICHAZ的M/A岛含量与尺寸均显著增大,而ICHAZ冲击吸收能量大幅降低;在冲击载荷的作用下,M/A岛会因周边的应力集中而极易成为裂纹源;M/A岛含量与尺寸的增加会使材料的冲击断裂机制由准解理断裂转变为解理断裂。

英文摘要：

To investigate the effect of M/A island on impact properties of inter-critical heat affected zone（ICHAZ）in T24 steel welding joint,subcritical normalizing on the T24 steel was carried out at different temperatures,and several tests such as scanning electron microscope（SEM）,transmission electron microscope（TEM）,Vickers hardness test and impact experiments were performed.The results show that,hard and brittle M/A islands distributed in the grain boundary of ICHAZ in the T24 steel suffered subcritical normalizing at different temperatures.With an increase in the normalizing temperature,the amounts and size of the M/A islands increased significantly and the impact absorbed energy decreased linearly.Under the impact load action,the M/A islands which located in grain boundaries could become crack sources easily due to the three dimensional stresses concentration.The impact fracture mechanism of the material changed from quasi-cleavage to cleavage as the relative amounts and size of the M/A islands increased.