The investigation of strength and plasticity mechanism of low-temperature annealed ultrafine grained stainless steel

Abstract

The properties of steel material can be greatly improved when its grain size becomes finer, so grain refinement is the most commonly used to improve the strength, ductility and impact on the toughness of steel at the same time. Compared to ordinary fine-grained steel, the average grain size of ultra-fine grained steel is less than 2 μm and it has different strength and plasticity mechanism. In this paper, effect of low-temperature annealing on the microstructure and properties of ultra-fine grained stainless steel in internal friction was studied by utilizing transmission electron microscope (TEM) and universal tensile testing machine. At the same time, the strength and plasticity mechanism of ultra-fine grained stainless steel was revealed by internal friction experiments. The results show that with the increase of annealing time and annealing temperature, both the tensile strength and yield strength decreases, while the elongation increases continuously. The mechanical properties of tested steel are more sensitive to the temperature. In the internal friction curve of tested steel, the peak of P1 which result from the interaction between solid solution atoms and dislocations increases first and then decreases, while the peak of P2 which result from the interaction between dislocation and carbide precipitates decreases first and then increases. The peak of P3 which result from the structure, area and movement of grain boundary decreases continuously. The strength and plasticity mechanism of tested steel at room temperature is the result of interaction between the grain boundary and dislocation.