Strain-rate effects on the recrystallization of molybdenum-based MZ17 alloy

Abstract

Warm compression tests were performed for the Mo-based alloy MZ17 (Mo-1.7% wt.-ZrO2). Macroscopic deformations to about 67% reduction in height were imposed to cylindrical specimens over a wide range of strain rates (from 10−1 to 10 s−1) at 1000 and 1100 °C to investigate the effects of both, the strain rate and deformation temperature on the recrystallization of the alloy. The compression tests were performed under high vacuum (< 5.0 × 10−4 mbar) using a deformation dilatometer followed by fast cooling. Stress-strain curves with very similar shapes can be noticed for all testing conditions. As-deformed microstructures were imaged at the center of the samples where plastic flow is more uniformly distributed using electron backscatter diffraction (EBSD) to distinguish the recovered domains from the recrystallized grains. Electron channeling contrast imaging (ECCI) was used to visualize the dislocation structures. At all tested temperatures and strain rates, only partial recrystallization was detected. The recrystallized volume fraction increases with increasing the strain rate. There is microstructural evidence of three restoration mechanisms acting during warm deformation; i.e., dynamic recovery, dynamic recrystallization and particle stimulated nucleation (PSN), the latter to a minor extent.