Shock-induced twinning and texture in a mild carbon steel

Abstract

Deformation twinning is investigated in a polycrystalline mild steel under shock compression to about 12 GPa. The free surface velocity history is measured to calculate twinning stress. The postmortem sample is characterized with electron backscatter diffraction (EBSD). We provide a method to calculate the activated twinning systems in all twinned grains from EBSD data. Twinning is completely activated and suppressed for grain size above 36μm and below 4μm, respectively. For intermediate grain sizes (14–30μm), twinning tends to occur in the grain orientations near 〈101〉, consistent with the Schmid factor analysis. Almost all the twins nucleate on the twinning systems with the largest or second largest Schmid factors. The twinning stress is 1.16 GPa, and critical resolved shear stress for twinning is 0.47 GPa. Twinning in weakly textured sample can induce a strong 〈001〉 fiber texture, as a result of its following the Schmid’s law.