The dependence of the tensile deformation behavior on the annealing temperature of a TRIP-aided lean duplex stainless steel

摘要

The tensile deformation behavior of a lean duplex stainless steel with metastable austenite phase was investigated after annealing at temperature ranges of 1000-1200°C. The evolution of microstructure during deformation was characterized by transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). The austenite fraction decreased almost linearly as the annealing temperature increased. The tested steel exhibited transformation induced plasticity (TRIP) at all annealing temperatures, resulting in an enhancement of strength and ductility, in which the best combination of strength and ductility with about 60GPa% was at 1050°C. This could be owing to not only the austenite fraction but also compositional partitioning. Microstructural observation showed that the deformation of austenite phase was mainly controlled by martensitic transformation in the sequence of γ-martensite ε-martensite α'. The deformation twins also were found in the deformed austenite which may lead to more or less twin induced plasticity (TWIP). In addition, the deformation mechanism of the other phase, ferrite was dominated by the slip of the dislocation. The plot of strain hardening rate (θ)-strain(ε) in the overall temperature range can be divided into two cases: (i) typical three stage hardening caused by TRIP and (ii) a particular multiple stage strain hardening cased by TRIP and TWIP as well as mutual competition.