Fig. 4: HRTEM observations of the IGC nanograined Fe-Ni samples before and after annealing at 300 °C for 1 h.

a This shows the dislocations (marked by T shape symbols) at the grain boundary region (marked by the dotted yellow line), FFT and a typical burgers circuit of the Fe-Ni sample before annealing. b HRTEM image of the 300 °C annealed Fe-Ni sample, showing the coexistence of BCC (electron beam is along the [111]) and FCC (electron beam is along the [110]) phases, and a dislocation-free nanograin.