Influence of lamellar and equiaxed microstructural morphologies on yielding behaviour of a medium Mn steel

Additional austenitization followed by quenching was introduced before the intercritical annealing (IA) of cold rolled medium Mn steel to produce the duplex microstructures having both lamellar and equiaxed morphologies, whose respective fractions vary with austenitization temperature. When it increased from 850°C to 1050°C, more martensite was formed during quenching and then transformed to the lamellar grains after the IA. At the same time, the higher austenitization temperature resulted in the greater microplasticity before macro-yielding, the decreases in both upper yield point and yield drop and the shorter yield point elongation. The relationship between all the yielding behavior and the microstructural morphologies were discussed on the basis that the lamellar and the equiaxed phase interfaces could have the different capability of emitting either partial or full dislocations during deformation.