The influence of annealing on the mechanical properties of double-phased metals

The dual-phase are produced by intercritical heat treatment and, getting a microstructure composed, basically, by ferrite and martensite, are detached by introduce typical characteristcs like high tensile strength, good ductility and conformability high rate of work-hardening and low yield stress. In the present work was studied the tensile behaviour of dual-phase steel in several conditions of tempering, with the purpose to investigate the ferrite - martensite interaction. The influence of different temperatures, used on the heat treatment, about the mechanical properties was related with microstructural parameters, like volumetric fraction, microhardness and phase morphology. The results showed that tempering caused reductions on martensitic volumetric fraction and phases microhardness, changing the dual-phase steels morphology. Furthermore, the elevation of tempering temperature occasioned a decreased on tensile strength levels and an increased on ductility. Was evidenced a yield stress elevation until 350°C, followed by a reduction on tension levels up this temperature, beside a discontinuity gradual return of the stress-strain curve. The results obtained for the tensile strength properties rising the importance of martensite volumetric fraction, such their chemical content carbon, because the elevation of tempering temperature caused a reduction on tensile strength levels. © Copyright 1993 Society of Automotive Engineers, Inc.