In-situ study of the effect of grain boundary misorientation on plastic deformation of Inconel 718 at high temperature

The effect of the grain boundary (GB) misorientation on plastic deformation of Inconel 718 (IN718) alloy was investigated in this paper, using in-situ tensile experiment at 650 °C in combination with crystal plasticity finite element method (CPFEM). The results indicate that dislocations tend to accumulate at GBs to form stress concentration, but the degree of stress concentration does not necessarily increase with the increase of the GB misorientation. It is attributed to the slip transfer at the GBs, determined by the angle between the slip systems of the two adjacent grains. There is a significant uncertainty in the slip transfer for GB misorientation larger than 10°. However, the \(m_{{{\alpha \beta }}}^{\prime} \left( {{\text{SF}}_{\alpha } + {\text{SF}}_\beta } \right)\) criterion, which is a function of the Luster and Morris \(m_{{{\alpha \beta }}}^{\prime}\) combining the Schmid factors of the two slip systems with the GB misorientation, has some statistical separation significance. Slip transfer tends to appear at GB misorientation less than 30° and \(m_{{{\alpha \beta }}}^{\prime} \left( {{\text{SF}}_{\alpha } + {\text{SF}}_\beta } \right) > 0.78\). This study clarifies the mechanism of the influence of GB misorientation on IN718 microplastic deformation and provides a new strategy to study the deformation behavior of superalloys.