Deformation-induced softening in drawn nickel microwires during torsion

Abstract

Starting from two different initial diameters, nickel microwires of 100 µm diameter were drawn with total drawing strains of 1.5 and 4.6. Tension and torsion tests were performed to examine their mechanical behavior. Electron back scattered diffraction (EBSD) was used for the Microstructural characterization. The drawn microwires showed normal strain hardening in tension; however, an interesting deformation-induced softening behavior was seen during torsion loading. The less drawn wire showed more torsional strength and a negative slope of hardening. A new mechanism for dislocation annihilation is proposed to explain this softening.