Dynamic Deformation Twinning in Shock-Loaded Iron

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Abstract
Deformation twinning has been observed in shock‐loaded samples of heat‐treated Ferrovac E iron at peak stresses from 3 to 16 kbar. In this range, the volume fraction of twins increases monotonically from zero to approximately 4%. In instrumented transmitted‐wave measurements stress relaxation was observed behind the elastic precursor for propagation distances of 12 mm or greater, but not at smaller distances. An analytical description of dynamic deformation twinning which adequately describes experimental observations on shock‐wave propagation in Ferrovac E iron is proposed. This analysis is based on models for the growth of twin platelets combined with the equation γ=kα relating the plastic strain γ to the twinning shear k and the volume fraction of twins α. Dynamic deformation twinning in impact‐loaded solids appears to be fairly well established both from experimental and analytical points of view and certainly must be considered as a possible physical mechanism in the description of plastic flow at high strain rates.