The phase field crystal model (PFCM) is employed to simulate the process of multi-grain solidification and its subsequent spinodal decomposition in a binary alloy system. Simulation results show that the PFCM can reproduce the whole process of the important material processing phenomena of multi-grain solidification, including nucleation, growth, coarsening and grain boundary formation. Furthermore, the PFCM can also successfully simulate the full course of the multi phase transformation process from solidification to spinodal decomposition.