Effect of microstructure on the dynamic deformation behavior of dual phase steel

The high-speed deformation behavior of a commercially available dual phase steel composition was studied by means of split Hopkinson bar testing in shear punch mode. The as-received cold-rolled material was subjected to a variety of heat treatment conditions to produce several different microstructures, namely ferrite plus pearlite, ferrite plus bainite and/or acicular ferrite, ferrite plus bainite and martensite, and ferrite plus different fractions of martensite. A strong effect of microstructure on both static and dynamic properties and on the dynamic factor (ratio of dynamic to static strength) was observed. According to the variation of dynamic factor with static strength, three groups of microstructures with three distinct behaviors were identified. Under the same static strength level, the classic dual phase microstructure was found to have the highest value of dynamic factor and therefore can absorb more dynamic energy than other microstructures.