Interfacial microstructure evolution, growth kinetics and mechanical properties of Fe/Al dissimilar metal joints

The interfacial microstructure evolution, growth kinetics of the intermetallic compound (IMC) and mechanical properties of Fe/Al dissimilar metal joints were investigated by vacuum diffusion bonding. The results show that there is no IMC formed on the interface of the joint bonded at temperature of 550 ℃. When the bonding temperature exceeds 575 ℃, the interfacial region is composed of Fe2Al5 and a small amount of FeAl3, and the thickness of IMC layer increases rapidly with the increase of bonding temperature.Under the bonding time of 120 min, the shear strength of the joint increases first and then decreases with the increase of the bonding temperature, and the shear strength of the joint reaches the maximum value of 37 MPa.According to thermodynamic theory, the Gibbs free energy change of Fe2Al5 is the lowest in the range from 550 ℃ to 625 ℃, and then followed by that of FeAl3, and the generated sequence of interfacial IMC can be: Fe2Al5→FeAl3. The interfacial IMC grow in a parabolic manner as a function of bonding temperature, and its growth activation energy is 282.6 kJ·mol-1.The growth rates of IMC at the interface are 1.13× 10-14, 3.59×10-14, 1.21×10-13 m2·s-1 at 575, 600, 625 ℃ respectively