Abstract��Flow curves of warm deformation performed on martensite structure(M) and ferrite plus pearlite structure (F+P) in a medium carbon steel were determined on Gleeble3500 machine. And the effect of strain rate on the warm flow behavior of the two starting microstructures of M and F+P at various temperatures was studied comparatively. It is found that the strain rate sensitive index(m) and the working softening effect of M are larger than that of F+P. And the flow stress of M is lower than that of F+P under the conditions of strain rate of 0.001s-1 and deformation temperature at 600��, 650�� and 700��. When the strain rate ranges from 0.01 to 10.0s-1, there are critical strain values at which the M flow curves intersect the F+P curves under some conditions. In these cases, if the strain amount is larger than the critical strain, the martensitic flow stress is lower than that of F+P. These results show that, M structure, compared with F+P structure, may be a promising candidator for steel��s warm working. Additional, the mechanisms that result in these characteristics of M flow behavior are also discussed.
2010, Vol. 28 
