Propagation of localized slip bands in low-temperature deformation of Cu–Be

Wire samples of different diameters of homogenized commercial Cu–Be alloys are deformed, displacement controlled, in a liquid helium bath at strain rates between 5×10−3 and 5×10−1 s−1. For a considerable fraction of samples where the strain rates are well above the transition between regular serrations and extended regular patterns, strong irregularities occur. For load versus time diagrams where regular patterns occur, indicating the propagation of deformation bands from one grip to the other, band propagation velocities are determined. The velocities decrease with increasing stress level and increasing sample thickness, but increase with increasing strain rate in qualitative agreement with theoretical findings. The results confirm the occurrence of propagating deformation bands and qualitatively support the theory.