Dynamic Recrystallization in Cu-Cr-Zr-Ti Alloy Under Large Plane Strain Conditions

Abstract

The Cu-Cr-Zr-Ti alloy was subjected to single-hit plane strain compression tests in the temperature range of 923 K to 1073 K (650 degrees C to 800 degrees C) and at two different strain rates of 0.1 and 1 s(-1). These tests were performed to ascertain the kinetics of microstructural evolution resulting by dynamic recrystallization (DRX) in the alloy under hot deformation conditions. The differences in the extent of DRX under various deformation conditions were established by plotting fractional softening as a function of strain and time. Further, the Avrami exponent was found to decrease with increase in deformation temperature. This was attributed to early onset of recrystallization leading to subsequent work hardening of the recrystallized grains and grain growth at higher temperatures which results in the loss of nucleation sites due to reduced grain boundary area. Microstructural observations made using optical microscopy, scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD) revealed nucleation to occur in the following steps: elongation of grains perpendicular to the compression direction, bulging of elongated grain boundaries due to strain-induced boundary migration (SIBM), and subsequent subgrain formation behind the bulged boundary due to strain-induced low-angle boundaries. Finally, the equation describing the DRX kinetics under plane strain conditions for the alloy was established as X = 1 - exp [-0.455 x ((epsilon - epsilon(c))/epsilon(p))(2.84)].