Detection of plastic deformation gradients in steel using scanning SQUID microscopy

Scanning SQUID microscopy is shown to be capable of detecting deformation gradients when accompanied by significant changes in hardness. Deformation which does not increase the dislocation density (as measured by the increase in hardness) has little effect. The effect can be produced by different techniques including cold rolling and tensile deformation. The effect is shown to occur in at least two different alloys with very different microstructures indicating the possibility of wide applicability.