Crystallographic aspect of shear bands formation in pure iron deformed at high strain rates

Abstract

In this paper results on shear bands developed in pure iron are presented. The main focus was put on microstructural characterization and crystal lattice rotation in sheared regions. The hat-shaped samples were deformed at a high strain rate of 560 s−1 using a drop-hammer. The microstructure of deformed specimen was investigated by optical microscopy and scanning electron microscopy equipped with a high-resolution electron backscattered diffraction facility. The changes of mechanical properties in the band area and neighbouring matrix were investigated using nano-indentation test. This paper clearly shows that initial stages of shear bands formation are associated with the formation of kink-type bands. The orientation maps revealed the crystallographic determination of the shear band formation. During deformation in each grain located within the sheared region, one of the {110}-type planes situate along the macro-shear band plane and <111> direction situates along the shear direction. In consequence, the formation of specific texture components within the shear band region was observed, different from texture observed in deformed matrix. In micro-scale no effects of dynamic recrystallization were observed. Nano-hardness tests indicated that notable increase of strain hardening is related to the strain localization in narrow shear band’ regions, while the matrix undergoes almost no deformation.