Tensile Surface Morphology Research Articles

THE MICROSTRUCTURE AND TENSILE FRACTURE BEHAVIOR OF LONG TERM THERMAL AGED Z3CN20-09M STAINLESS STEEL

Cast austenite stainless steels (CASS) were widely used in the primary circuit piping of pressurized water nuclear reactors (PWRs), for their excellent mechanical behavior, corrosion resistance and good weldability. CASS, however, were known to have a tendency of thermal aging embrittlement after long term service at mid-temperature (about 280—320 ). The microstructures, micro-mechanical properties and tensile fracture behaviors of Z3CN20-09M stainless steels, thermal aged at 400 for 2×10 4 h, were studied in this work. TEM was utilized to observe the microstructure. A nano-indenter was used to investigate the micro-mechanical properties. The tensile tests were completed by an in situ fatigue tester. The tensile surface morphology was observed in SEM and the fracture of thermal aged CASS was examined by an electron probe micro-analyzer (EPMA). The results indicated that the spinodal decomposition and G-phase precipitation distributed in ferrite of the aged CASS. The nano-hardness of ferrite increased and the plastic deformation ability