Effect of thermomechanical processing on structure and mechanical properties of WNiCo Einfluss der thermomechanischen Veredelung auf Struktur und mechanische Eigenschaften der Wolframschwerlegierung WNiCo

Abstract

The study characterizes the effects of intensive plastic deformation, realized by the rotary swaging method, on the deformation behavior of WNiCo tungsten heavy alloy samples. To assess the differences in the deformation behaviors of the samples, evaluated via uniaxial compression tests (UCT), and characterize the microstructures, i. e. occurrence and development of hardening/softening processes, two different temperatures of swaging (900 °C and 1200 °C), and two different uniaxial compression testing temperatures (1100 °C and 1200 °C), were used. A relatively high strain rate of 10 s⁻¹ was chosen for the testing because of the typical use of the tungsten heavy alloy for kinetic penetrators. The achieved results indicate that the development of softening processes, especially dynamic recrystallization, can occur within the swaged material, depending on the processing/testing conditions. Swaging at the lower temperature of 900 °C introduced significant work hardening and accumulation of strain, which promoted the development of dynamic recrystallization during the subsequent hot temperature testing. Swaging at 1200 °C, on the other hand, facilitated dynamic recrystallization and relaxation (especially within the nickel-cobalt matrix) already during processing, which consequently increased the activation energy necessary for the development of recrystallization during the hot testing.