Effects of temperature distribution on plasticity in laser dieless drawing

摘要

Temperature measurement based on grey body radiation spectrum is used to determine the temperature profile of hot wires in the deformation region in laser dieless wire drawing, with spatial resolution down to a few micrometers. The Voce parameters characterizing the high temperature plastic flow behavior of the wires are calculated using the temperature and diameter profiles of the wires in the deformation region. These parameters are determined for as-drawn and annealed pure nickel wires of 500 μm diameter. Recrystallization and grain growth during the drawing process are studied. The effects of temperature, grain size and precursor wire diameter on wire drawability and strain rate are analyzed. The measured temperature and diameter profiles agree well with theoretical results. Grain growth increases rapidly with increasing temperature after recrystallization, and the grain size follows the thermal activation law. The effective activation energy increases for larger wire diameter. Surface morphology of the drawn wires and strain rate calculation show that dislocation motion is the dominant deformation mechanism.