The abnormal behavior of monotonic stress-strain curves of aluminum alloys induced by the yield drop with increasing strain rate or decreasing temperature is considered based on the relaxation model of plasticity. The plastic deformation of 2519A and 2519A-T87 aluminum alloys within the strain rate range from 0.001 to 6000 s<sup>-1</sup> and temperature range from -45 to 450°С is analyzed from the standpoint of determining the structural and temporal characteristics of the material invariant to the strain rate. It is proposed to determine the change in the structural and temporal characteristics caused by the test temperature choice by analyzing a set of strain rate dependences of the material constructed at a fixed temperature. The temperature dependences of the characteristic relaxation time as a velocity sensitivity parameter of the relaxation plasticity model are compared for 2519A and 2519A-T87 aluminum alloys. Theoretical nonmonotonic stress-strain curves in a wide strain rate range of 0.001-6000 s<sup>
