Strain Rate-Dependent Deformation Mechanisms in CMSX-4 at 800 °C: Insights from Full-Field Optical Extensometry

The deformation behaviour of a Ni-base single crystal superalloy is studied using a multiscale approach incorporating a recently developed videography arrangement, allowing for full-field digital image correlation. Single crystal CMSX-4 in the 001 001 orientation was used to obtain a significant tensile dataset spanning temperatures from ambient to 900 °C and strain rates from 10 −1 to 10 −5 s −1 . A multiscale approach was applied particularly to three strain rates at 800 °C, to determine transitions in the deformation mechanisms. It is demonstrated that the macroscopic deformation patterns correlate well with microscopic observations; moreover, the full-field strain mapping offers useful insights into the underlying shear and slip events. The strain rate sensitivity was particularly pronounced in the regime emphasised and evidence is presented for transitions in deformation mechanism within a single test as deformation proceeds.