Effect of Strain Rate on Dynamic Softening Behavior of Low Carbon Steel during Deformation above Austenite Transformation Temperature
Using a Gleeble-1500 thermal simulation testing machine,a low carbon microalloyed steel was subjected to compression deformation at 4 different strain rates(10,7,3,1s-1)above Ac3 temperature(950℃),and then quenched.The stress-strain curve of high temperature deformation was transformed by the double differential method,and it is found that there are two main softening mechanisms in the process of material deformation,namely dynamic phase transformation and dynamic recrystallization.With the increase of deformation rate,the two critical stresses for material softening increase linearly.The two critical strains do not change much with the change of the strain rate.The metallographic structure of the material after quenching was observed with a metallographic microscope.It is found that the width of the Widmanst ätten ferrite laths within the material decreases with strain rate increasing and the number of polygonal ferrites increases with strain rate increasing;Widmanstätten ferritic laths are generally in a parallel or perpendicular relationship,while Widmanstätten ferritic laths in perpendicular relation do not present a strictly right angle,but rather deviate from a certain angle.
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