The sintering–alloying processes of nickel (Ni), iron (Fe), and magnesium (Mg) with aluminum (Al) nanoparticles were studied by molecular dynamics simulation with the analytic embedded-atom model (AEAM) potential. Potential energy, mean heterogeneous coordination number , and surface atomic number N _surf–A were used to monitor the sintering–reaction processes. The effects of surface segregation, heat of formation, and melting point on the sintering–alloying processes were discussed. Results revealed that sintering proceeded in two stages. First, atoms with low surface energy diffused onto the surface of atoms with high surface energy; second, metal atoms diffused with one another with increased system temperature to a threshold value. Under the same initial conditions, the sintering reaction rate of the three systems increased in the order MgAl < FeAl < NiAl. Depending on the initial reaction temperature, the final core–shell (FeAl and MgAl) and alloyed (NiAl and FeAl) nanoconfigurations can be observed.