NEAR-CRACK-TIP DEFORMATION IN COPPER SINGLE-CRYSTALS

Abstract

Cracked Cu specimens, made by diffusion bonding two halves of a single crystal, were 3-point bend tested, and the surfaces near the crack tips were examined by an optical microscope and a stylus profilometer. The plastic zone developed as assembled fan-shaped sectors, the details of which depended on the crystal orientation. A sector was often characterized by a family of dominant slip lines, and operations of slips on coplanar slip planes (CSP) were mutually exclusive. The through-thickness displacement changed gradually across sector boundaries but its gradient did not, suggesting a constant plastic strain within a sector but strain discontinuites at sector boundaries. The degree of necking depended mostly on the operation of slips on non-CSP, but operation of CSP caused either local necking or protrusion depending on the crystal orientation.