The observation of slip phenomena in single crystal Fe samples during in situ micro-mechanical testing through orientation imaging

Abstract

This paper reports a study of local orientation change occurring within micro-scale tensile samples as a function of strain. These samples were fabricated from a thin film of single crystal bcc Fe and deformed in tension using an in situ micro-mechanical testing device inside a scanning electron microscope. Samples were loaded along the <110> direction parallel to the specimen axis, strained to different levels, and then subjected to electron backscatter diffraction scans over the entire area of the gauge section. Analysis of the surface orientation data shows that, within a necked zone of the micro-sample gauge section, there are two distinct regions of significant orientation change, in which local crystal rotations occur in opposite directions. These two regions are separated by an intermediate band that shows minimal misorientation from the original state. Crystal rotations within the two regions that develop opposite orientations are found to be consistent with classic single crystal slip, where the slip direction rotates toward the tensile axis. It is shown that increasing tensile strain causes an increasing degree of rotation away from the starting orientation. The tests also illustrate the occurrence of slip on at least two different slip systems, based on the slip traces and orientation change. © 2014 Microscopy Society of America.