The Studies Of Fe-Al-Zn Ternary Systems By Mechanical Alloying

The hot-dip galvanizing is a commonly used corrosion technology in the field of steel protection. In the hot dip galvanizing process, aluminum is the most commonly used alloying elements, and therefore, Fe-Al-Zn ternary system has been the focus of research in the field of iron and steel protection.The evolving structure, microscopic morphology of the Fe-Al-Zn ternary mixed powder after mechanical alloying and subsequent heat treatment process have been investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) etc. The results show that the binary powder mixture with the nominal composition of Fe-25at%Zn, was fully alloyed after milling for25h, and the solid solution of Fe(Zn) formed. It is found the precipitation of г-Fe3Zn10phase after10days heat treatment at temperature340℃. The Al5Fe2-Znx solid solution structure was eventually formed from the mixed powder with the nominal composition of Fe-62.5at.%Al-12.5at.%Zn by mechanical alloying. The structure does not change after10days heat treatment at temperature340℃. The Al5Fe2-Znx solid solution formed by mechanical alloying from the mixed powder with the nominal composition of Fe-60at.%Al-20at.%Zn. And it decomposed into the Al5Fe2intermetallic compound and Zn solid solution after10days heat treatment at temperature340. Moreover, as for the mixed powder with the nominal composition of Fe-83.3at.%Zn-8.3at.%Al, the mechanical alloying process was interrupted after milling about twenty hours due to excessive cold welding. And there is no observable new phase. The δ-FeZn10(Al) phase was observed after the heat treatment at temperature340℃for10days.According to Miedema Theory and the geometric extrapolation model proposed by Ouyang et al, the formation enthalpies of Fe-Zn and Fe-Al-Zn systems were calculated. The results show that the formation enthalpies of Fe3Zn10and Fe2Al5are the lowest, which indicate these compounds are stable compound and are in good agreement with experimental results.The amorphous formation range of Fe-Al-Zn system was also predicted based on the point of view of thermodynamics. The results of predicted amorphous formation range for Fe-Al binary system coincide well with the experiment result. The amorphous formation range of Fe-Al-Zn system is narrow and mainly distributed in Zn-poor part, which indicates that the addition of Zn in Al-Fe is not benift to the amorphization.