High strain rate deformation induced by high-velocity forming of 100Cr6 steel

Paper in proceeding, 2008

This paper concerns the development of the near-net-shape manufacturing technique of high-velocity forming. The microstructural response to the high strain-rate deformation was evaluated for 100Cr6 steel in two differently heat treated conditions: spheroidise annealed (hardness 250 HV) and quenched and tempered (330 HV). A high-velocity pressing machine was used to conduct the forming tests on cylindrical specimens. By applying different impact velocities on samples with varying sizes deformation mechanisms could be related to strain and strain rate. Extreme localization of deformation resulting in white etching bands was seen in quenched and tempered samples but not in spheroidise annealed samples. Furthermore, the strain and strain rates were shown to affect the tendency for extreme localization. No white etching bands were found in samples strained to less than 1. Appearance of white etching bands could be seen in the macroscopic shape of the samples where the more homogeneously deformed samples showed a typical barrel shape while the strongly localized samples were slightly more bell shaped. It can be concluded that for high-velocity forming to be applicable to 100Cr6 steel a careful choice of the combination strain/strain rate needs to be made.