Investigation of Strain Hardening in NiAl Single Crystals Using Three-Dimensional FEA Models

Single crystals of NiAl are very ductile at intermediate temperatures (400–700 K) and were observed to exhibit high strain hardening rates at large strains when loaded in the [110] orientation. The experimentally observed strain hardening in NiAl single crystals could not be predicted using simple hardening models and two-dimensional finite element analysis. The primary slip systems that activate during the deformation are (010)[100] and (100)[100], however, it has been hypothesized that activation of secondary slip on {011} slip planes may be responsible for the high rate of hardening observed. The hardening of intermetallic single crystals when multiple slip systems are activated is not well understood. To study this further, a three-dimensional hardening model and constitutive equations were implemented into a finite element analysis program. Since the parameters required to describe the hardening model such as latent hardening ratios are difficult to obtain experimentally, a parametric study was conducted to estimate values for these parameters that enable the prediction of the experimentally observed load versus elongation curves.