Deformation behavior of the cobalt-based superalloy Haynes 25: Experimental characterization and crystal plasticity modeling

The deformation behavior of a wrought, cobalt-based superalloy, Haynes 25, was studied using a combination of experimental techniques and crystal plasticity modeling. The microstructure was examined by transmission electron microscopy and electron backscattered diffraction to determine the deformation and hardening mechanisms contributing to the mechanical behavior of the alloy. A high density of stacking faults within the grains, consistent with planar glide, was found to be the predominant defect mechanism with no evidence of deformation twinning observed. A strain-rate and temperature-sensitive hardening law that includes effects of planar glide was developed for the material and implemented in a self-consistent homogenization scheme. The hardening of individual crystals is based on the evolution of dislocation densities per plane and includes the effects of strain rate and temperature through thermally activated recovery and dislocation interactions. The model is validated on a comprehensive set of compression tests performed at temperatures ranging from 298 to 673 K and strain rates ranging from 10−3 to 2600 s−1 and found capable of reproducing the stress–strain response and texture for all tests with a unique set of single-crystal hardening parameters.