The microstructure evolution and mechanical properties of a ZK60 magnesium alloy produced by the semi-solid thermal transformation （SSTT） route and the recrystallization and partial melting （RAP） route were studie...The microstructure evolution and mechanical properties of a ZK60 magnesium alloy produced by the semi-solid thermal transformation （SSTT） route and the recrystallization and partial melting （RAP） route were studied, respectively. The microstructure evolution during partial remelting was studied at different temperatures for different time. The tensile mechanical properties of thixoformed components by the two routes at room temperature were examined. The results show that coalescence is dominant in the SSTT alloy and Ostwald ripening is dominant in the RAP alloy. Compared with the SSTT route, the RAP route can produce finer semi-solid microstructure under the similar isothermal holding condition. The microstructure of the RAP alloy is much more spheroidized compared with the SSTT alloy. Thixoforming for the ZK60 magnesium alloy produced by the SSTT and RAP route results in successful filling of the die, and the thixoforming process improves the mechanical properties of ZK60 magnesium alloy. The RAP alloy shows significantly advantageous mechanical properties over that of the SSTT alloy.展开更多
Structural and compositional transitions of Datong coal ash and its CaCO3 additional effects were carefully exam- ined at a temperature range of 300 to 1 600℃ by using XRD and solid state NMR. The quantitative estima...Structural and compositional transitions of Datong coal ash and its CaCO3 additional effects were carefully exam- ined at a temperature range of 300 to 1 600℃ by using XRD and solid state NMR. The quantitative estimation of amorphous structures of ashes can be successfully obtained through the analyses of solid state NMR spectra. Viscosity of molten ash and its changes with CaCO3 addition were also evaluated up to 1 700 ℃ by using a rotary type viscometer. Glasses with poor crystalline and amorphous phase were continuously formed through the eutectic reaction of silica above fusing temperature （FT〉1 500 ℃） that caused broadening and shift of 29Si and 27A1 peaks in NMR results. With the additional amount of CaCO3 increasing, the peaks shifted to downfield obviously; the fraction of Si（OA1）0（OSi）4 decreased, while that of Si（OA1）l（OSi）l at 84.3 x 10-6 increased apparently. These transitions indicated the destruction of large alumina-silicate framework into small segments by the addition of Ca ion.展开更多
文摘The microstructure evolution and mechanical properties of a ZK60 magnesium alloy produced by the semi-solid thermal transformation （SSTT） route and the recrystallization and partial melting （RAP） route were studied, respectively. The microstructure evolution during partial remelting was studied at different temperatures for different time. The tensile mechanical properties of thixoformed components by the two routes at room temperature were examined. The results show that coalescence is dominant in the SSTT alloy and Ostwald ripening is dominant in the RAP alloy. Compared with the SSTT route, the RAP route can produce finer semi-solid microstructure under the similar isothermal holding condition. The microstructure of the RAP alloy is much more spheroidized compared with the SSTT alloy. Thixoforming for the ZK60 magnesium alloy produced by the SSTT and RAP route results in successful filling of the die, and the thixoforming process improves the mechanical properties of ZK60 magnesium alloy. The RAP alloy shows significantly advantageous mechanical properties over that of the SSTT alloy.
文摘Structural and compositional transitions of Datong coal ash and its CaCO3 additional effects were carefully exam- ined at a temperature range of 300 to 1 600℃ by using XRD and solid state NMR. The quantitative estimation of amorphous structures of ashes can be successfully obtained through the analyses of solid state NMR spectra. Viscosity of molten ash and its changes with CaCO3 addition were also evaluated up to 1 700 ℃ by using a rotary type viscometer. Glasses with poor crystalline and amorphous phase were continuously formed through the eutectic reaction of silica above fusing temperature （FT〉1 500 ℃） that caused broadening and shift of 29Si and 27A1 peaks in NMR results. With the additional amount of CaCO3 increasing, the peaks shifted to downfield obviously; the fraction of Si（OA1）0（OSi）4 decreased, while that of Si（OA1）l（OSi）l at 84.3 x 10-6 increased apparently. These transitions indicated the destruction of large alumina-silicate framework into small segments by the addition of Ca ion.
