Microstructure and mechanical properties of laser beam welded joints of China low-activation ferritic/martensitic steel with cerium addition

•RE-CLF-1 steel joint was prepared by LBW, and PWHT of the joint was performed.•The joint with PWHT was composed of fine tempering martensite and precipitates.•Vickers hardness of the base material of the joint with PWHT was the lowest.•The joints under tensile tests were fractured at the base material.•DBTT of the joint with PWHT was comparable to the base material. The microstructure and mechanical properties of the CLF-1 steel with Ce doping (RE-CLF-1 steel) joints prepared by laser beam welding (LBW) were investigated in this work. Post weld heat treatment (PWHT) of the joint was performed at 720 °C for 2 h. Results show that no visible cracks and pores can be observed in the welded joint. The RE-CLF-1 steel joint after PWHT was composed of much fine tempering martensite and precipitates in the fusion zone. Vickers hardness test shows that the hardness was decreased linearly from the fusion zone to base metal, and no softening effect was observed in the heat-affected zone. The tensile strength of the joint at room temperature was 664 MPa, which was larger than that of the CLF-1 steel. All the samples under tensile tests were fractured at the base metal, indicating good tensile behavior of the joint. Additionally, the ductile-brittle transition temperature of the RE-CLF-1 steel was about ∼40 °C, which was comparable to that of the un-welded RE-CLF-1 steel.