Study On Phase Equilibria Of The Al-Si-Ti-Fe Quaternary System And Related Ternary System At700℃

Hot-dip aluminizing is an important and effective protection technology of steel,Due to the formation of a multi-layer interface between the substrate and the moltenaluminum alloy during hot-dipping, a coating with an corrosion resistance, hightemperature oxidation resistance and corrosion resistance sulfide gas can be obtained.However, despite achievement, the hot-dip aluminizing is need more efforts. But thereis still some problems, for example, the coating is too thick, both the fluidity ofaluminum bath and a coating with the adhesion are badly. The problems affect thequality of the surface coating of steel parts production efficiency and post molding. Inthis work, by adding alloy elements into the aluminum bath, produce aluminumcoating with good quality. So the Al-Si-Ti-Fe quaternary system’s phase equilibriuminformation at the aluminizing temperature is important to understand the synergisticeffect of Si and Ti in Al-Fe coatings during hot-dip aluminizing on the microstructureof the coating. So determination of the phase relationships of the Al-Si-Ti-Fequaternary system is very important to aluminizing industry.Based on SEM-EDS analyses and XRD results, the700°C isothermal sections ofAl-Si-Ti, the Al-Si-Ti-Fe quaternary system with Al being fixed at90and at75at.%,and the related ternary systems are determined in the present work. The mainconclusions are listed as follows: Fourteen three-phase regions have been determinedexperimentally in the isothermal section at700°C: τ1+(Si)+L-Al, τ1+(Si)+TiSi2, τ1+τ2+L-Al, τ1+TiAl3+L-Al, τ1+τ2+TiSi, τ1+TiSi2+TiSi, TiAl3+τ2+TiSi,TiAl3+Ti5Si4+TiSi, TiAl3+Ti5Si3+TiSi, TiAl3+Ti5Si3+TiAl2, Ti5Si3+TiAl2+TiAl, Ti5Si3+Ti3Al+TiAl, Ti5Si3+Ti3Al+α-Ti, Ti5Si3+Ti3Si+α-Ti. The ternaryphases τ1and τ2are confirmed in the system at700°C. The compositions of τ1and τ2are found as Al6.2-9.3Ti32.4-34.0Si57.5-60.9and Al10.0-11.6Ti34.2-34.5Si53.9-55.6, respectively. Onethree-phase regions i.e., L-Al+TiAl3+Fe4Al13are found in the Al-rich portion ofAl-Ti-Fe system. Four three-phase regions, i.e., L-Al+τ5+TiAl3, L-Al+τ5+τ6, L-Al+τ6+τ4and L-Al+τ4+(Si) are found in the Al-rich corner of the Al-Si-Fe system.Two four-phase regions exist in the isothermal section of the Al-Si-Ti-Fe quaternarysystem at700°C with Al being fixed90at.%: L-Al+τ5+TiAl3+Fe4Al13and L-Al+τ5+τ6+TiAl3. Six four-phase regions have been identified experimentally in theisothermal section of the Al-Si-Ti-Fe quaternary system at700°C with Al being fixed 75at.%:(Si)+τ1+τ4+L-Al, τ1+τ4+τ6+L-Al, TiAl3+τ2+τ6+L-Al, TiAl3+τ5+τ6+L-Al, TiAl3+τ5+Fe4Al13+L-Al and τ1+τ2+τ6+L-Al. The new phase are notfound in the section of the Al-Si-Ti-Fe quaternary system. Ti are almost not soluble intheτ6, τ5, Fe4Al13and L-Al phase, respectively. The maximum solubility of Si in TiAl3,Fe4Al13and L-Al is13.4,4and11.2at.%, respectively. Fe are almost not soluble inthe τ1, τ2, TiAl3and L-Al phase, respectively.