The main aim of the paper is to estimate the deformation mechanism of
the high-temperature deformation in the Al-Zn-Mg-Cu alloys (V95 and ON
Z 42 4222). The results of tensile tests, especially of the measuremen
t of strain rate sensitivity parameter m are given. The structure chan
ges observed using light and transmission electron microscopy are docu
mented. The phenomenological model based on the concept of a threshold
stress is tested.