Effect Of Crystalline On Corrosion Propertry And Thermal Conductivity Propertry Of FeCoCrMoCBY Amorphous Alloy

In this dissertation, Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂（at%） bulk metallic glass with adiameter of3mm was prepared by copper mold casting and nano-crystallineFe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂alloys were obtained by annealing. The characteristic andcrystallization processess of amorphous alloys were identified by X-ray diffraction（XRD）, TG/DTA synchronous thermal analyzer and scanning electron microscope（SEM）, respectively. A comparative study of the corrosion behaviors of amorphous andamorphous/nanocrystalline alloys was performed by marinate method in aqua regiasolution, potentiodynamic polarization method and electrochemical impedancespectroscopy （EIS） in1.5M HCI solution, and the corrosion morphologies of thesamples after marinated and potentiondynamic polarization test were observed by SEM.The effect heat-treated techniques at610℃,630℃and645℃for3h （Ar as shieldinggas） on the structure and corrosion resistance of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂amorphousalloy were synthetically analysed. The results show the different structures and phases（Fe3B, Cr3C2, Cr23C6） are intimately involved in the corrosion resistance of samples,Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂amorphous alloy with homogeneous composition andstructure displays excellent anti-corrosion ability than that of the heat-treated samples.The order of anti-corrosion ability of amorphous/nanocrystalline alloys from strong toweak is amorphous alloy,630°C×3h,610°C×3h,645°C×3h. But the downward trend ofthe corrosion resistance is not obvious based on electrochemical kinetic parameters Icorrand R₁of amorphous/nanocrystalline alloys, which are still on the same order asamorphous alloy. Moreover, the thermal diffusivity and thermal conductivity ofnano-crystalline Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂alloys and amorphous alloy were measuredin the temperature of300K,375K,425K,495K and525K by laser indeed thermalconductivity tester. The effect of heat-treated temperatures and time on thermalconductivity of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂amorphous alloys was studied, and therelationship among the thermophysical properties, structure and temperature wasdiscussed. The results show Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂amorphous alloys heat-treated at700°C for1h has equal-fine grains, and the average grain size is48nm, crystallizationfraction is10.5%, its thermal conductivity decreases to0.803W/mk from of1.51W/mkof un-treated amorphous alloy at room temperature. While the heat treatment time isextended4h, although the average grain size increases a little, but the crystallization fraction is up to62.9%, its thermal conductivity is0.726W/mk at room temperature.The crystallization fraction of amorphous alloy heat-treated at900°C for4h issignificantly increased （100%）, but the average grain size is only about57nm, and itsthermal conductivity is reduced to0.698W/mk at room temperature. And the thermalconductivity of samples were measured in the different temperatures, the order size ofthe thermal conductivity was also λ（amorphous）> λ（700℃×1h）> λ（700℃×4h）>λ（900℃×4h）, this indicates that the thermal conductivity of nano-crystallineFe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂alloys have the decreasing tendency with the increasing ofcrystalllization fraction, but the grain size slightly increase. Besides, the thermaldiffusivity value of amorphous Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂alloys andamorphous/nanocrystalline alloys are small, as well as in the order of10^-7, that ofamorphous Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂alloys is only2.57×10^-7m²Â·s^-1at roomtemperature.