Evolution of iron aluminide in Al/Fe in situ composites fabricated by plasma synthesis method

The evolution of intermetallic compounds for Al/Fe in situ composites fabricated by the plasma synthesis method (PSM) was investigated through the microstructural analyses for the partially reacted particle region. The partially reacted particle is composed of Al/Al13Fe4/Al5Fe2/Fe layer. Based on the concept of effective free energy of formation, the first phase that nucleates on the interfacial layer of Al/Fe is determined as Al13Fe4. By the reaction of Al13Fe4 and Fe, Al5Fe2 forms and grows inward. Due to heat extraction by the reaction, the edge of Al13Fe4 dissolves to form angular Al13Fe4 in the matrix. By the reaction and decomposition of Al/Fe through the intermediate phase of Al5Fe2, the Fe particles transform to Al13Fe4 in the plasma synthesis method. In addition, the differences of main intermetallic compounds between by the hot dipping process and by the plasma synthesis method were discussed.