EFFECT OF Mg AND TEMPERATURE ON Fe–Al ALLOY LAYER IN Fe/(Zn–6%Al–x%Mg) SOLID–LIQUID DIFFUSION COUPLES

Abstract

Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe–Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe–Al alloy layer. It was found that the Fe2Al5Znxphase layer forms close to the iron sheet and the FeAl3Znxphase layer forms near the side of the melted Zn–6%Al–3%Mg in diffusion couples. When the Fe/(Zn–6%Al–3%Mg) diffusion couple is kept at 510[Formula: see text]C for more than 15[Formula: see text]min, a continuous Fe–Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples, the Fe–Al alloy layer on the interface of the Fe/(Zn–6% Al–3% Mg) diffusion couple is the thinnest. The Fe–Al alloy layer forms only when the diffusion temperature is above 475[Formula: see text]. These results show that the Fe–Al alloy layer in Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples is composed of Fe2Al5Znxand FeAl3Znxphase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe–Al alloy layer. When the Mg content in the Fe/(Zn–6%Al–[Formula: see text]%Mg) diffusion couples is 3%, the growth of the Fe–Al alloy layer is inhibited. These results may explain why there is no obvious Fe–Al alloy layer formed on the interface of steel with a Zn–6%Al–3%Mg coating.