Study On Phase Equilibrium Of Zn-Si-Zr Ternary System

Hot dip galvanizing is a more convenient and effective process in the steel anticorrosion method.Among them,the zinc-aluminum alloy coating has both the durability protection characteristics of aluminum and the cathodic protection characteristics of zinc,and its corrosion resistance compared with the single element coating.It is several times higher than the pure zinc coating.The immersion plating temperature is lower than that of aluminum plating,and the corrosiveness of the zinc pot is relatively small.It has developed rapidly in recent years.Galvalume coating is a kind of popular Zn-Al alloy coating for the industry.However,because the coating is too thick,it can lead to many problems,such as too much residue in the bottom.At the same time it also hinders the development of coating.The study found that adding alloying elements can be used to reduce the thickness of galvalume coating and residue.In particular,Zr element is chemically active and can react with Al to form ZrAl3 in a cast aluminum alloy to form a heterogeneous core,refine grains,and improve performance.Also can inhibit the Fe-Zn reaction in hot dip galvanizing.In order to study the microstructure and formation process of 55%Al-Zn coating by the synergistic effect of Si and Zr,the stability of alloy phase and the effect of adding elements on the microstructure of 55%Al-Zn coating were evaluated.In this work,the phase relationship of Zn-Si-Zr ternary system is studied.Research achievements for rich zinc base alloy database and develop new galvanized aluminum alloy has strong guiding significance and application value.Experimental methods contain diffusion coupling method and equilibrium alloy method.By means of metallographic microscope,scanning electron microscope and energy spectrometer?SEM-EDS?and X-ray method,The relationship between the phase relationship of 450?and 600?of Zn-Si-Zr ternary system and it's liquid-surface projection is studied experimentally.Experimental results show that there are eleven three-phase zones in the isothermal section at 450?.The experiment measured ten three-phase zones,which are:L-Zn+?Si?+Si₂Zr,L-Zn+Si₂Zr+SiZr,L-Zn+Zn₁₄Zr+SiZr,Zn₁₄Zr+SiZr+Si₄Zr₅,Zn₁₄Zr+Zn₆Zr+Si₄Zr₅,Zn₆Zr+Zn₃Zr+Si₄Zr₅,Zn₃Zr+Si₄Zr₅+Si₂Zr₃,Zn₃Zr+Si₂Zr₃+SiZr₂,Zn₃Zr+Zn₂Zr+SiZr₂ and ZnZr+?Zr?+SiZr₂.The three-phase zone Zn2Zr+ZnZr+SiZr2 can be launched according to the phase law.The solubility of Zn in Si2Zr,SiZr,Si4Zr5,Si2Zr3 and SiZr2 is 2.6,3.0,5.7,7.1 and 4.7 at.%.The solubility of Si in Zn₁₄Zr,Zn₆Zr,Zn₃Zr,Zn₂Zr and ZnZr is 0.8,2.4,2.4,1.8 and 2.3 at.%.Experimental results show that there are twelve three-phase areas in the isothermal section at 600?.The experiment measured ten three-phase zones,which are:L-Zn+?Si?+Si2Zr,L-Zn+Si2Zr+SiZr,L-Zn+SiZr+Zn23Zr6Si,L-Zn+Zn₆Zr+Zn₂₃Zr₆Si,Zn₆Zr+Zn₃Zr+Zn₂₃Zr₆Si,SiZr+Si₄Zr₅+Zn₂₃Zr₆Si,Si₂Zr₃+Si₄Zr₅+Zn₂₃Zr₆Si,Si₂Zr₃+Zn₃Zr+Zn₂₃Zr₆Si,Zn₂Zr+Zn₃Zr+SiZr₂ and Zn₂Zr+ZnZr+SiZr₂,The three-phase zone Zn₃Zr+Si₂Zr₃+SiZr₂ and?Zr?+ZnZr+SiZr₂can be launched according to the phase law.The solubility of Zn in Si₂Zr,SiZr,Si₄Zr₅,Si2Zr3 and SiZr2 is 2.4,1.2,6.7,3.2 and 5.3 at.%.The solubility of Si in Zn6Zr,Zn3Zr,Zn₂Zr and ZnZr is 0.2,3.2,1.3 and 0.8 at.%.At the same time,we found the phase Zn₂₃Zr₆Si is existing at 600?.Through the study of the liquid phase surface projection diagram of zinc-rich angle of Zn-Si-Zr ternary system,it is found that there are eight primary phases of zinc-rich angle in the system,namely:?Zn?,Zn₁₄Zr,Zn₆Zr,Zn₂₃Zr₆Si,Zn₂Zr,SiZr₂,Si₄Zr₅,SiZr and?Si?.Five ternary eutectic reactions:L?SiZr+Zn₁₄Zr+?Zn?,L?Zn₁₄Zr+Si₄Zr₅+?Zn?,L?Zn₆Zr+Zn₁₄Zr+Si₂Zr₃,L?Zn₂Zr+Zn₃Zr+SiZr₂ and L??Si?+SiZr+?Zn?.Two peritectic reactions:L+SiZr₂?Zn₂₃Zr₆Si and L+SiZr?Si₂Zr.