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The development of non-equilibrium segregation of boron at grain boundaries in Fe-4 0%Ni alloy during continuous cooling process was experimentally observed with boron Particle Tracking Autoradiography (PTA) and Transmission Electron Microscopy (TEM,). The samples with 10ppm boron were cooled at 2℃/s to 1040, 980, 920, 860, 780 and 640℃ respectively after pre-heat treatment of 1150℃ for 15mm with a Gleeble-1500 heat simulating machine, then water quenched to room temperature. The width of segregation layer and boron depletion zone, rich factor and other parameters were measured by a special image analysis system. The experimental results of PTA show that the grain boundary segregation of boron during cooling process is a dynamic process and the development of the non-equilibrium segregation experiences three stages: first increases rapidly from 1150 to 1040℃, then gently from 1040 to 860℃, and rapidly again from 860℃ to 640℃. The width of boron depletion zone increases from about 11μm at 1040℃ to 26μm at 640℃. TEM observation shows that boron precipitates exist at grain boundaries when the samples are cooled to below 860℃. The experimental phenomena are briefly discussed.
The development of non-equilibrium segregation of boron at grain boundaries in Fe-4 0% Ni alloy during continuous cooling process was experimentally observed with boron Particle Tracking Autoradiography (PTA) and Transmission Electron Microscopy (TEM,). The samples with 10ppm boron were cooled at 2 ° C / s to 1040, 980, 920, 860, 780 and 640 ° C respectively after pre-heat treatment of 1150 ° C for 15mm with a Gleeble-1500 heat simulating machine, then water quenched to room temperature. The width of segregation the experimental results of PTA show that the grain boundary segregation of boron during cooling process is a dynamic process and the development of the non-equilibrium segregation experiences three stages: first increases rapidly from 1150 to 1040 ° C, then gently from 1040 to 860 ° C, and rapidly again from 860 ° C to 640 ° C. The width of boron depletion zone increases fr om about 11 μm at 1040 ° C. to 26 μm at 640 ° C. TEM observation shows that boron precipitates exist at grain boundaries when the samples are cooled to below 860 ° C. The experimental phenomena are briefly discussed.