Plastic deformation of polyethylene crystals on copper and NaCl crystal substrates

Polyethylene single crystals deformed on copper and NaCl single‐crystal substrates by the method of Gleiter and Argon were examined in transmission electron microscopy attached to carbon film carriers constraining them to their deformed state and also after they have been removed from the deformed substrates and were allowed to relax. It was observed that the imposed shear strains can be accommodated by the polyethylene crystals by a combination of debonding from the substrate, elastic flexing, extensive inplane twinning and martensitic shear transformations, buckling, and tearing. No contrast effects suggestive of slip lines could be observed in dark field studies, and the gold droplet decoration technique failed to detect any unambiguous slip lines. From this it is concluded that the critical shear stress for slip is always higher than that for twinning and martensitic shear transformations, and that crystals will deform preferentially by these latter modes.