Study On Phase Equilibrium Of Zn-Al/Fe-Co-Sb Quaternary System

In the field of the corrosion protection of modern steel,hot dip galvanizing has been widely used,and it makes the plated parts get excellent coating.But because of the Sandelin effect,the silicon in steel gives rise to dull grey and excessively thick coating with poor adhesion.At present,it has been proved that adding proper amount of alloying elements to the zinc bath can effectively improve the structure and surface quality of the coating.Sb can effectively promote the formation of spangle on the surface of the coating.Al can improve the luster and toughness of galvanized steel.For steel with high content of silicon,adding appropriate amount of Co can effectively inhibit the silicon reactivity of steel.However,in the actual scientific research,there are few studies on the synergistic reaction between Al,Co,Sb and zinc bath.So it is necessary to research the phase equilibrium relationship of the Zn-Al-Co-Sb and Zn-Fe-Co-Sb quaternary system.The research of this topic can be divided into two aspects as follows:?1?By means of the SEM-EDS and XRD analysis of the equilibrium alloy,the450 and 600°C isothermal sections of Zn-Al-Co-Sb quaternary system with Zn fixed at 93 at.%have been determined in this study.Four four-phase regions and nine three-phase regions have been confirmed in the isothermal section at 450°C.Three four-phase regions and seven three-phase regions have been confirmed in the isothermal section at 600°C.The maximum solubilities of Zn in AlCo,Al₅Co₂ and Al₁₃Co₄ are 4.89 at.%,18.98 at.%and 7.85 at.%,respectively.No new ternary and quaternary compounds have been detected in this study.?2?By means of the SEM-EDS analysis of the equilibrium alloy,the 450°C isothermal section of Zn-Fe-Co-Sb quaternary system with Zn fixed at 93 at.%have been determined in this study.Because of the?(FeZn₁₃)and?₂(CoZn₁₃)form a continuous solid solution at 450°C,so the yellow area of the isothermal section is a wide range of three-phase region which contains two morphology:L+Sb₂Zn₃+??rich-co?and L+Sb₂Zn₃+??rich-fe?.The maximum solubility of Co in the??rich-co?phase is 5.94at.%,and the maximum solubility of Fe in the??rich-fe?phase is6.24at.%.No new ternary and quaternary compounds have been detected in this study.