Study On Phase Equilibria Of The Al-Zn-Fe-Ti Quaternary System And Related Ternary System At600℃

Hot-dip galvanizing is one of the main measures used to protect steels fromcorrosion. However, with the industrial development, specific needs not assisted byzinc coatings appeared. For this reason, in the1960s, hot-dip Zinc-Aluminum becamethe focus in hot-dip industry. Among them, the55%Al-Zn coating is developedrapidly because of its excellent performance in resistance to corrosion. But someproblems still exist in the actual production process, for example, the poor processingformability and bottom dross caused by vigorous reaction between Al and Fe. Addingalloy elements, such Ti, Si Mg and RE etc., in the bath to change the sort andformational order of intermetallics in the alloy layer and bath is a feasible solution tothese problems. It involves the phase equilibria of Al-Zn-Fe-M（M=Ti，Si，Mg，RE etc.）quaternary system. In this work, the Al-Zn-Fe-Ti quaternary system and relatedternary system are investigated to lay the theoretical fundament of analyzing the effectof Ti in hot-dip galvalume.In this work equilibrated alloys were utilized with the help of scanning electronmicroscope equipped with dispersive X-ray spectroscope and X-ray power diffractionto determine the phase relations in Al-Zn-Fe-Ti quaternary system with Al being fixedat75at.%and50at.%at600°C and Zn-Al-Ti ternary system at600°C and450°C.The results of research indicate that, there exist two four-phase fields:αAl+TiAl₃+FeAl₃+Liq and Ti₂Al₅+TiAl₃+FeAl₃+Liq, in Al-Zn-Fe-Ti quaternarysystem with Al being fixed at75at.%. The existence of Ti₂Al₅, which only appear athigh temperature （above1150°C） in Ti-Al binary system, is confirmed at600°C.There are nine four-phase fields: Liq+TiZn₃+Ti₂Al₅+FeAl₃, Liq+TiZn₃+τ₃+FeAl₃,Fe₂Al₅+FeAl₃+τ₃+τ₂，Fe₂Al₅+FeAl+τ₃+τ₂，Liq+Fe₂Al₅+τ₃+T，Liq+Fe₂Al₅+FeAl+T，Fe₂Al₅+FeAl+τ₃+T，τ₂+TiZn₃+τ₃+FeAl₃and L+Fe₂Al₅+FeAl₃+τ₃in Al-Zn-Fe-Tiquaternary system with Al being fixed at50at.%. τ₃is the extension of Al-Fe-Titernary phase Al8FeTi₃, τ₂is a ternary phase in Al-Fe-Ti ternary and T is the extensionof Zn-Fe-Ti ternary phase TiFe2Zn22. No new quaternary phase was found in thissection. In Zn-Al-Ti ternary system, there exist ten three-phase regions:αAl+TiAl₃+Liq， Ti₂Al₅+TiAl₃+Liq， TiZn₃+Ti₂Al₅+Liq， TiZn₃+TiAl₂+Ti₂Al₅，TiZn₃+TiAl+Ti₃Al， TiZn₃+Ti₃Al+T2，TiAl₃+TiAl₂+Ti₂Al₅and TiAl₂+TiAl+TiZn₃,T2+TiZn₃+TiZn and T2+Ti₃Al+TiZn。Correct the isothermal section of Zn-Al-Ti ternary system at450°C based on the results of predecessor and nine three-phaseregions have been found: αAl+TiAl₃+Ti₂Al₅, αAl+Ti₂Al₅+T, T+αAl+Liq,Liq+TiZn₁₆+T, TiZn₈+TiZn₁₆+T，TiZn₈+TiZn+T，TiZn₈+TiZn+TiZn₃，TiAl₂+Ti₂Al₅+Tand TiAl₂+Ti₂Al₅+TiAl₃。...