Effect of Processing Route on the Microstructure and Tensile Properties of an Al and Si-Bearing Medium Mn-Trip Steel Microalloyed with V

The dependence of processing route on the microstructure and tensile behavior was analyzed in a V microalloyed Mn-medium steel containing (in mass%) 3.5 Al and 1.2 Si. To obtain four different microstructures, as hot rolled (HR) band was divided in several parts and three of them were submitted to treatments consisting of annealing at 620 ºC (HRA), warm rolling (WR) or warm rolling followed by annealing at 600 ºC (WRA). It was observed the presence of a complex microstructure composed mainly of the mixture of austenite, martensite and delta ferrite in different amounts. Tensile test showed that the balance between these phases is the most important factor that contributes to the variation in the strength and ductility of this steel. At a given value of strain, the enhancement of strength observed in HR materials was related to a value of ferrite and martensite of up to 88%, while the higher total elongation to failure found in WR products was associated to the presence of about 60% of retained austenite. The combination of strength and ductility in the WRA product results in an ultrahigh product of strength and elongation of approximately 59.5 GPa %, which guarantee its usefulness for automotive applications