THE EFFECT OF MICROSTRUCTURE ON THE MECHANICAL-PROPERTIES AND ADIABATIC SHEAR-BAND FORMATION IN A MEDIUM-CARBON STEEL

Using a torsional split-Hopkinson bar, high strain rate tests in the order of 1000 s(-1) were conducted on 5 different heat treatments of a medium carbon steel. The heat treatments were; as received, fully annealed and air cooled and quench tempered at 315, 480 and 650 degrees C, each for 1 hour. The microstructures obtained were coarse pearlite, unresolved pearlite in a ferrite matrix and three different tempers of martensite. It was found that ferrite in the microstructures would always deform preferentially over any other phase present in the material. In addition, if the ferrite was uniformly distributed, the ASB would be uniformly deformed. However, when it was segregated, granular type shear band surfaces would be observed.