Study On Microstructure And Properties Of FeCrAl Alloy Prepared By Casting Strip And Conventional Process

With the rapid development of automobile industry,vehicle exhaust became one of the most important sources of air pollution in China.The new environmental protection policy put forward stricter requirements for vehicle exhaust purification carriers.In this context,as a widely used metal honeycomb carrier material,FeCrAl alloy not only needs good formability and corrosion resistance,but also should develop towards the direction of high temperature resistance and light weight to meet the use requirements of automobile.In view of this,in this paper,strip casting and conventional process were used to prepare FeCrAl alloy.The microstructure,mechanical properties,texture evolution and formability,high temperature oxidation resistance and corrosion resistance of FeCrAl alloy were compared.The main results are as follows:(1)The cold rolled and annealed sheets' structure and properties of FeCrAl alloy prepared by strip casting and conventional process were studied.When the annealing temperature is low,the grain size of cold rolled and annealed sheets prepared by strip casting and conventional process is similar,however,when the annealing temperature is over 1050?,the grain size of cold rolled and annealed sheets prepared by strip casting was significantly smaller than that of conventional process.In addition,the tensile properties of cold rolled and annealed sheets prepared by strip casting at ambient temperature and elevated temperature are almost the same as those of cold rolled annealed sheets prepared by conventional process.(2)The effect of annealing temperature on the texture evolution of FeCrAl alloy sheets prepared by strip casting and conventional process was studied.During the cold rolling process,?-fiber texture and weak ?-fiber texture with strong points of {001}<110>and{112}<110>were formed in the strip casting and conventional process cold rolled sheets respectively.With the increase of annealing temperature,the grains grow continuously,and the volume fraction of grains with<111>//ND oriented grains and the strength of y-fiber texture are also increasing.The y-fiber texture strength and<111>//ND oriented grain volume fraction of the cold rolled annealed sheets prepared by strip casting were smaller than those of the conventionall cold rolled and annealed sheets.Therefore,the r-value of the cold rolled and annealed sheets prepareed by strip casting were slightly lower than that of the cold rolled and annealed sheets prepared by conventional process.(3)The elevated cyclic oxidation behavior of hot rolled and annealed sheets prepared by strip casting and conventional process were studied.In the early stage of oxidation,the oxidation rate of hot rolled and annealed sheets prepared by strip casting were lower than that of hot rolled and annealed sheets prepared by conventional process,with the progress of oxidation,the oxidation rate of the two tended to be the same.The oxide film of the samples prepared by strip casting and conventional process are composed of ?-Al2O3,ZrO2-tetragonal and ZrO2-monoclinic.After 200h of cyclic oxidation,spalling area of oxide film of strip casting sample is 0.35%,which is better than that of conventional process sample by 1.76%,showing good exfoliation resistance.From the longitudinal section of the oxide film,the substrate and the alumina film interface of the strip casting and the conventional process samples are uneven,and the local growth of the oxide film to the substrate increases the adhesion of the oxide film.The specific surface area of the oxide film on the substrate is 1.89 times larger than that on the substrate,so the pinning effect of oxide film is stronger.After 200 hours of oxidation,the grains of the oxidized samples were coarsened,reaching 172.99?m and 206.04?m.Therefore,in the condition of long-term high-temperature service,compared with the conventional process samples,strip casting samples can reduce the brittleness of alloy materials due to the excessive grain size.(4)The corrosion resistance of cold rolled and annealed sheets prepared by strip casting and conventional process were studied.With the increase of cold rolled and annealing temperature,pitting corrosion potential of strip casting and conventional process increased first and then decreased,and the maximum value is 0.247V and 0.241 V at 950?.After 96h of FeCl3 solution immersion corrosion test,the weight loss rates of sheets prepared by strip casting and conventional process were 3.464g/(m2·h)and 3.619g/(m2·h).The corrosion resistance of the two samples was similar,there was no significant difference.