Microstructure evolution in Fe-based-aluminide metallic-intermetallic laminate (MIL) composites

Metallic-Intermetallic Laminate composites of Fe/Al, 430-SS/Al, 304-SS/Al were fabricated and investigated for the microstructure evolution, growth kinetics and microhardness distribution across the intermetallic/metal interfaces. Fe2Al5 phase was formed as dominant phase in the intermetallic layer of the Fe/Al MIL composites with parabolic growth rate behavior. A multilayer structure (namely a uniform layer and a eutectic layer) with a complex mix of intermetallic phases (Fe2Al5, Fe4Al13, Cr2Al13, Al5.5Cr1.95Fe2.55 and Al9Ni1.9Fe0.1) form in the Fe-alloy/Al MIL composites. The growth of the multilayers in the Fe-alloy/Al reaction can be described as a mixed kinetic growth mechanism that is diffusion controlled growth in the uniform layer, while it is interface controlled growth in the eutectic layer. The growth activation energies of Fe/Al, 430-SS/Al, 304-SS/Al reactions are 150 KJ mol−1, 200 KJ mol−1 and 220 KJ mol−1, respectively. The calculated intermetallic yield rate for pure Fe/Al, 430-SS/Al and 304-SS/Al MIL composites are 1.21, 1.16 and 1.10, respectively, which proved to be reliable for predicting the final intermetallic layer thickness in Fe-based MIL composites.