Molybdenum(Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry;however, the embrittlement of welded Mo joints limits its further applicat...Molybdenum(Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry;however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone(FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo_(2)C, and some free C atoms, and MoC and MoOxC yphases were also present. The distribution of Mo_(2)C directly influenced the bonding strength of the grain boundaries.As Mo_(2)C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo,it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo_(2)C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxC yphase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51775416)National Thousand Talents Program of China(No.WQ2017610446)supported by the Project of Innovation Team of Xi'an Jiaotong University(No.XTR0118008)。
文摘Molybdenum(Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry;however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone(FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo_(2)C, and some free C atoms, and MoC and MoOxC yphases were also present. The distribution of Mo_(2)C directly influenced the bonding strength of the grain boundaries.As Mo_(2)C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo,it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo_(2)C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxC yphase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.
