Tensile Testing of Ni-Based Single Crystal Superalloys: What Is the Correct “Point of View”?

The anisotropyAnisotropy of deformation of a single crystal superalloySingle crystal superalloy is studied using a newly designed furnace arrangement which allows for videography from multiple apertures and subsequent digital image correlationDigital image correlations (DIC). Thus, for initially cylindrical specimens, the full field of surface strain is measured at a 25 μm spatial resolution. Our approach is tested for STAL15 along each of the <001>, <011>, and <111> crystallographic orientations at 800 °C. The time-dependent anisotropic deformation along each of these crystallographic directions is quantified. Crystal plasticityCrystal plasticity finite element (CPFE) calculations are used to rationalise the observations; it is demonstrated that the predictions are particularly sensitive—on account of the plastic anisotropiesAnisotropy—to the boundary conditions used for the loading. Implications for the testing of single crystal superalloysSingle crystal superalloy are discussed in detail, with a particular view towards improving testing protocols.