Deformation Twinning in Pure Nickel Induced by a High-Current Pulsed Electron Beam

Recent experimental evidence has shown that face-centered-cubic materials that are not normally associated with deformation twinning will twin during moderate high-current pulsed electron beam (HCPEB) processing. In this paper, we present an experimental investigation of deformation twinning in pure multi-crystalline nickel exposed to HCPEB irradiation from a Nadezhda-2 HCPEB device. The samples, which were irradiated with various numbers of pulses, were examined. The formation of a large number of twin lamellae on the treated surface was observed in the regions without surface melting. Moreover, a large strain located at the twin lamellae deformation was found. Transmission electron microscope analysis revealed that the deformation twinning was indeed triggered during the HCPEB irradiation. This suggests that the very high stresses and superfast strain rates induced via the rapid heating and cooling caused by the HCPEB irradiation lead to deformation twinning in coarse-grained nickel.