Dynamic softening behavior of Al-18Si alloy produced by spray forming

Abstract

The high-temperature deformation behavior and dynamic softening transition from dynamic recrystallization (DRX) to dynamic recovery (DRV) of Al-18 wt.%Si alloy was studied by torsion tests in a temperature range of 573similar to773 K and a strain rate range of 0.001similar to1/sec. The alloy was produced by spray-forming followed by hot extrusion. The dependence of flow stress (sigma) on strain rate (epsilon) and temperature (T) could be described by the power Arrhenius relationship, epsilon = A sigma(p)(n) exp(-Q/RT). The activation energy and stress exponent values were higher at the low temperature region than those at the high temperature region. The alloy showed a flow curve of DRX in the temperature range of 573similar to673 K, while at 673similar to773 K, the alloy exhibited a flow curve of DRV. These results were analyzed by observing the shapes of the flow curves throughout the deformation condition. Also, the transition behavior from DRX to DRV has been investigated through observation of deformed microstructure and flow curves during hot deformation.