Fracture Toughness of Fe-Zn Intermetallic Compound Layer

Abstract

The Fe-Zn intermetallic compounds (IMC) layers composed of δ_p, δ_k, and Γ phases were fabricated using two different kinds of Fe/Zn diffusion couple (DC), and the fracture toughness of the constituent phases was estimated from the toughness of the IMC layers. In the DCs with sufficient Zn supply, the IMC layers were mainly composed of δ_p phase after isothermal holding at 450-600 °C for 60 s, while in the DCs with limited Zn supply, the IMC layers were composed of δ_p, δ_k, and Γ phases at the early stage of isothermal holding, which was later dominated by Γ phase with further isothermal holding. The average grain size of the IMC phases was found to increase with increased holding temperature. From the comparisons between the IMC layers composed mainly by either δ_p or Γ phases, toughness of Γ phase was found inferior to that of δ_p phase. In addition, it was demonstrated that the toughness of δ_p and Γ was found to increase with decreased average grain size. Whereas, from the results using the multi-phase IMC layers, the toughness of δ_k phase was found almost equivalent to that of Γ phase.