The thermal aging of duplex stainless steel of nuclear power primary coolant piping in the actual environment is explored.The Z3CN20-09 Mduplex stainless steel was treated by thermal aging in the air or simulation conditions at 350 ℃.The mechanical properties of the steel after two different thermal aging was measured by small punch test.The fracture morphology of the specimen was observed by scanning electron microscopy(SEM),and the influence of the environment and time on the fracture mechanism was analyz...