The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatP ro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 al...The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatP ro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L ＋ γ→ L ＋ γ ＋ M_7C_3 →γ ＋ M_7C_3 →γ ＋ M_7C_3 ＋ M_（23）C_6→γ ＋ M_（23）C_6 and L → L ＋ δ→ L ＋ δ ＋ γ→ L ＋ δ ＋ γ ＋ M_（23）C_6→δ ＋ γ ＋ M_（23）C_6, respectively. The solidification mode was determined to be the austenitic mode（A mode） in HK40 alloy and the ferritic–austenitic solidification mode（FA mode） in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr_（23）C_6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.展开更多
An Fe–44Ni nanocrystalline（NC） alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods an...An Fe–44Ni nanocrystalline（NC） alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods and chemical analysis approaches. The results show that the NC film is composed of a face-centered cubic phase（γ-（Fe,Ni）） and a body-centered cubic phase（α-（Fe,Ni）） when it is annealed at temperatures less than 400℃. The corrosion resistance increases with the increase in grain size, and the corresponding corrosion process is controlled by oxygen reduction. The NC films annealed at 500℃ and 600℃ do not exhibit the same pattern, although their grain sizes are considerably large. This result is attributed to the existence of an anodic phase, Fe0.947Ni0.054, in these films. Under this condition, the related corrosion process is synthetically controlled by anodic dissolution and depolarization.展开更多
基金he financial support provided by the National High-Tech Research and Development Program of China (No. 2012AA03A511)
文摘The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatP ro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L ＋ γ→ L ＋ γ ＋ M_7C_3 →γ ＋ M_7C_3 →γ ＋ M_7C_3 ＋ M_（23）C_6→γ ＋ M_（23）C_6 and L → L ＋ δ→ L ＋ δ ＋ γ→ L ＋ δ ＋ γ ＋ M_（23）C_6→δ ＋ γ ＋ M_（23）C_6, respectively. The solidification mode was determined to be the austenitic mode（A mode） in HK40 alloy and the ferritic–austenitic solidification mode（FA mode） in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr_（23）C_6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.
基金financially supported by the Major State Basic Research Development Program of China (No. 2014CB643300)the National Natural Science Foundation of China (No. U1560104)the National Environmental Corrosion Platform (NECP)
文摘An Fe–44Ni nanocrystalline（NC） alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods and chemical analysis approaches. The results show that the NC film is composed of a face-centered cubic phase（γ-（Fe,Ni）） and a body-centered cubic phase（α-（Fe,Ni）） when it is annealed at temperatures less than 400℃. The corrosion resistance increases with the increase in grain size, and the corresponding corrosion process is controlled by oxygen reduction. The NC films annealed at 500℃ and 600℃ do not exhibit the same pattern, although their grain sizes are considerably large. This result is attributed to the existence of an anodic phase, Fe0.947Ni0.054, in these films. Under this condition, the related corrosion process is synthetically controlled by anodic dissolution and depolarization.
