Investigation of mechanical twinning via measurements of temperature and strain fields

Wrought magnesium exhibits deformation complexity with high load path dependency and plastic anisotropy. Lightweight magnesium AZ31 is widely used in literature for twinning investigations due to the ease of {1012}(1011) tensile twin activation under favorable loading conditions. Coordinated propagation of twinning leads to strain localization across the aggregate in the form of macroscopic shear bands. When the load is reversed after twin growth, material undergoes detwinning that is crystallographic orientation transformation of twinned grains to the original position. The contributions of this thesis built on the previous OM-DIC studies are composed of two independent channels. First, a notched sample design is used to guide conjugate shear bands into predetermined diagonal corridors and enforce their overlap at a prefixed location to study the physics of the overlap with OM-DIC. Secondly, the energetic aspects of material deformation with emphasis on twinning and detwinning have been studied by in situ infrared thermography. The primary goal of this part is to reveal the stored energy in the material over cyclic deformation that entails twinning/detwinning and slip plasticity regimes. Absolute temperature measurements with IRT conducted are successfully achieved by attaching an undeformed (free hanging) reference material next to the actual sample and the temperature data considered is the differential between deformed and undeformed material. Further, the reference material is also thermally insulated from the sample during by inserting a thermal isolator for more robust results. In the big picture, these experimental results will help the validation of higher fidelity crystal plasticity models for magnesium.