Intergranular strain and texture in steel Luders bands

Neutron diffraction was used to examine residual strains and deformation texture related to Luders bands phenomenon in uniaxially deformed mild steel samples. Samples of two different thickness, 1.5 mm (thin) and 3.0 mm (thick), were uniaxially deformed to between 0.5% and 20% engineering strain, followed by unloading. The shape and texture of the Luders bands depended on the sample thickness. Neutron diffraction texture measurements indicated that there was little texture within the Luders bands in the thicker samples. There was, however, significant texture in the Luders bands of the thinner samples, and this same texture intensified once the Luders bands covered the entire sample and up to 20% deformation. The residual strains in the Luders bands were similar for both sample thicknesses. In the bands the {2 0 0} planes exhibited the largest intergranular strain; even at only 1% deformation, the {2 0 0} strain in the Luders band was very high (400με). These high {2 0 0} strains were present only in the transverse and normal directions, with essentially no {2 0 0} strain in the rolling (applied stress) direction. Intergranular strains in the {2 2 0} and {2 1 1} were much lower and displayed much less variation with sample direction. In all samples the intergranular strains were essentially constant in the bands until the bands had propagated fully across the sample (∼5%) after this there was a small but progressive increase in the intergranular strains up to 20% deformation.