Lattice rotations during compression deformation of a [011] Ta single crystal

The slip-system symmetry along 〈011〉 in body-centered cubic materials is such that the 〈111〉 Burgers vectors on potentially active {110} and {112} slip planes lie within a single {011} plane. In the absence of friction, this affords the opportunity for (macroscopically) homogeneous large-strain deformations by compression. The constitutive response of four specimens in the [011] orientation deformed to 10, 20, 30, and 40% engineering strain, exhibited an up-turn in the true stress–true strain curves at approximately 25%. The primary objective of this investigation was to determine the degree of inhomogeneity of the deformation resulting from the platen/sample interface friction, as related to material modeling. To accomplish this, a simple analytical model was adapted and implemented within a 3D finite-element code to simulate the influence of friction on the measured constitutive response and estimate the associated lattice rotations in the specimen corners. Orientation imaging microscopy (OIM) was applied to characterize the lattice rotations and other mesoscopic features of the deformed microstructures. OIM revealed organized patterns of alternating crystal orientation (deformation bands) that evolved as a function of strain.