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Tensile tests of Fe-30Mn-5Si-2Al steel were carried out for different strains of 0.05,0.14,0.26,and up to the strain-to-failure in order to observe the evolution of microstructure during deformation and investigating the strain hardening behavior.Three-stage strain hardening behavior was observed in this steel during tensile test.In stage Ⅰ,planar dislocation structure was observed by TEM and regarded as main deformation mechanism,and low strain hardening rate exponent was exhibited.Primary deformation twinning occurred in stage Ⅱ,and the strain hardening rate exponent increased due to the blockage of dislocations’ motion by twin boundaries.In stage Ⅲ,the strain hardening rate exponent had increased to a value higher than 0.5.The obstacle effect of twin boundaries and twin-twin interaction had been observed by TEM,and the interactions between primary and secondary twins were found to cause the additional hardening in addition to the obstacle effect on dislocations’ motion,which led to the twinning induced plasticity effect in the later stage of deformation.
Tensile tests of Fe-30Mn-5Si-2Al steel were carried out for different strains of 0.05,0.14,0.26, and up to the strain-to-failure in order to observe the evolution of microstructure during deformation and investigating the strain hardening behavior. Three-stage strain hardening behavior was observed in this steel during tensile test. In stage I, the planar dislocation structure was observed by TEM and considered as the main deformation mechanism, and low strain hardening rate exponent was exhibited. Primary deformation twinning occurred in stage II, and the strain hardening rate exponent increased due to the blockage of dislocations’ motion by twin boundaries. In stage III, the strain hardening rate exponent had increased to a value higher than 0.5. The obstacle effect of twin boundaries and twin-twin interaction had been observed by TEM, and the interactions between primary and secondary twins were found to cause the additional hardening in addition to the obstacle effect on dislocations’ motion, which l ed to the twinning induced plasticity effect in the later stage of deformation.