Large Scale Dislocation Dyniamics Simulation of Precipitation Hardening in Ni-based Superalloys

The precipitation hardening in Ni-based superalloys, which contain up to 73{\%} volume fraction of $\gamma '$, has been investigated by large scale 3D dislocation dynamics simulations. Dislocations glide under external stress across a {\{}111{\}} plane of $\gamma $/ $\gamma '$ phase, intersected by cubic $\gamma '$precipitates. The critical resolved shear stress (CRSS) has been investigated for different microstructureal parameters: $\gamma '$volume fraction, anti-phase boundary (APB) energy and channel width. It is shown that the CRSS depends on the square root of the volume fraction of $\gamma '$. The CRSS is linearly proportional to the APB energy. Stuctures with a non-uniform distribution of $\gamma '_{ }$have CRSS that is 20{\%}-30{\%} smaller than a stucture with unique $\gamma '$ size corresponding to the average size of the non-uniform disribution of $\gamma '$. The fact is that the channel width is not uniform and some channel width is larger than the average channel width of a stucture with a non-uniform distribution of $\gamma '$, which makes the dislocation line easier to bend. This reveals that the channel width plays more important role than the $\gamma '$ size. When channel width decreases to about 20nm, CRSS weakly depends on the $\gamma '$size and increases dramatically.