Diffusion growth of ϕ ternary intermetallic compound in the Mg-Al-Zn alloy system: in-situ observation and modeling

Abstract Study on the diffusion growth of ternary intermetallic compounds in Mg-Al-Zn based light-weight alloys is important due to its close interrelation with alloy property. However, there is a very lack of existing data due to difficulties in both experimental and computational aspects. The current work aims at presenting the experimental observation on the diffusion growth behavior of ϕ phase at 360 °C as well as calculating its composition-dependent interdiffusion coefficients. We designed and successfully fabricated four Mg-τ ternary diffusion couples annealed at 360 °C for different times, where the diffusion path goes across the ϕ phase region and the diffusion growth of ternary intermetallic compound can be solely detected. In-situ observation of the time-dependent growth of ϕ phase was performed to accurately determine the parabolic growth constant. The experimental data were then subjected to a numerical inverse method to generate a set of self-consistent interdiffusivities of the ternary intermetallic compounds, which can reproduce the presently observed diffusion growth behavior of ϕ ternary intermetallic compound in Mg-τ diffusion couples.