Investigation of stress-strain response, microstructure and texture of hot deformed pure molybdenum

Abstract

The deformation behavior of pure molybdenum (Mo) was studied in very high temperature range (1400–1700 °C) by carrying out uniaxial compression tests at four different strain rates (0.01–10 s−1). Three types of stress-strain curves including work hardening, steady state and softening behavior were observed depending upon the deformation condition. The strain rate sensitivity (m) map generated from the flow stress data revealed two domains of high m values - one at about 1400 °C and 10−1 s−1 and the second one at ~1700 °C and strain rate of 10−2–1 s−1. The kinetic analysis of the deformation data yielded the apparent activation energy as 390 kJ mol−1, the stress exponent as 8.5, and the activation volume about 100–600 b3 for pure Mo. Microstructures of the deformed samples were investigated using the electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The appearance of smaller strain-free grains along the boundaries of deformed grains indicated the occurrence of dynamic recrystallization (DRX) in the samples deformed at conditions corresponding to the high m values. Grain growth was significant at higher temperature and lower strain rate deformation. Bulk texture measurements of the hot deformed samples indicated strengthening of 〈001〉 fiber texture during occurrence of the DRX.