Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni ...Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni alloys were studied. The results show that the GFA of Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) is improved successfully with the Y addition. The highest GFA appeares at x=6, while the reduced glass transition temperature (Trg) is 0.5225 and the supercooled liquid region(ΔTx) is 42.06 K; the position of the main diffraction halo is different for the alloys, and the maximum of the main diffraction halo of alloys with x=0, 1, 3 corresponds to the main peaks of a metastable fcc-Mg6Ni or fcc-Mg6Ni + Ni-Y intermetallic phases, and for the alloys with x=6, 10, it corresponds to Mg-Y and Ni-Y intermetallic phases; the micro-hardness of the alloys is improved with Y additions, and the highest micro-hardness is obtained at x=6 at.%, which is 960 MPa.展开更多
The temperature dependence of the viscosity of liquid Al-12wt.%Sn-4wt.%Si was studied with a hightemperature viscosity apparatus.Anomalous changes of viscosity of the melt were found at 1,103 K and 968 K in the coolin...The temperature dependence of the viscosity of liquid Al-12wt.%Sn-4wt.%Si was studied with a hightemperature viscosity apparatus.Anomalous changes of viscosity of the melt were found at 1,103 K and 968 K in the cooling process,which indicates anomalous structural changes of the melt.It is calculated that the anomalous structural change is associated with an abrupt decrease of atomic clusters'size and activation energy in the melt.According to the temperature of the anomalous structural changes,melt heat treatment process(quenching from superheat to pouring temperature) was performed on Al-12wt.%Sn-4wt.%Si melt prior to pouring,aimed to keep the small atomic clusters from higher temperature to lower pouring temperature.The results suggest that relatively small atomic clusters at the pouring temperature in the melt could generate a deep under-cooling of nucleation in the subsequent solidification process,and refine the as-cast structure.After being quenched from superheating to pouring temperature,the relatively small atomic clusters,especially the Si-Si clusters in the melt will grow to equilibrium state(relatively big atomic clusters) with holding time,resulting in the prominent coarsening of the Si morphology in the as-cast structure.展开更多
With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sinter...With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sintering have been investigated. The results show that Zn-Al eutec-toid microstructure can be achieved through their powders’ sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, in which Zn can dissolve into Al whereas Al can hardly dissolve into Zn. During sintering, a diffusion-solution zone a’ has formed and subsequently transformed into a eutectoid microstructure in the cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by the diffusion-solution zone α’. If the diffusion-solution zone α’ is unsaturated, it will have much more crystal defects and the combination between α’ and phase P is weak, thus the process of phase boundary sliding becomes easily; on the展开更多
基金supported by the Award Fund for Outstanding Young Scientist in Shandong Province, China (No. BS2011CL004)
文摘Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni alloys were studied. The results show that the GFA of Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) is improved successfully with the Y addition. The highest GFA appeares at x=6, while the reduced glass transition temperature (Trg) is 0.5225 and the supercooled liquid region(ΔTx) is 42.06 K; the position of the main diffraction halo is different for the alloys, and the maximum of the main diffraction halo of alloys with x=0, 1, 3 corresponds to the main peaks of a metastable fcc-Mg6Ni or fcc-Mg6Ni + Ni-Y intermetallic phases, and for the alloys with x=6, 10, it corresponds to Mg-Y and Ni-Y intermetallic phases; the micro-hardness of the alloys is improved with Y additions, and the highest micro-hardness is obtained at x=6 at.%, which is 960 MPa.
基金supported by the Key Subject (Laboratory) Research Foundation of Shandong Provincethe Natural Science Foundation of China (No.50871047)+1 种基金the Encouragement Foundation for Distinguished Young Scientist of Shandong Province (No. 2008BS04018)the Natural Science Foundation of Shandong Province (No.Y2006F55 and No.Y2007F69)
文摘The temperature dependence of the viscosity of liquid Al-12wt.%Sn-4wt.%Si was studied with a hightemperature viscosity apparatus.Anomalous changes of viscosity of the melt were found at 1,103 K and 968 K in the cooling process,which indicates anomalous structural changes of the melt.It is calculated that the anomalous structural change is associated with an abrupt decrease of atomic clusters'size and activation energy in the melt.According to the temperature of the anomalous structural changes,melt heat treatment process(quenching from superheat to pouring temperature) was performed on Al-12wt.%Sn-4wt.%Si melt prior to pouring,aimed to keep the small atomic clusters from higher temperature to lower pouring temperature.The results suggest that relatively small atomic clusters at the pouring temperature in the melt could generate a deep under-cooling of nucleation in the subsequent solidification process,and refine the as-cast structure.After being quenched from superheating to pouring temperature,the relatively small atomic clusters,especially the Si-Si clusters in the melt will grow to equilibrium state(relatively big atomic clusters) with holding time,resulting in the prominent coarsening of the Si morphology in the as-cast structure.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 59871031 and 59871025).
文摘With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sintering have been investigated. The results show that Zn-Al eutec-toid microstructure can be achieved through their powders’ sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, in which Zn can dissolve into Al whereas Al can hardly dissolve into Zn. During sintering, a diffusion-solution zone a’ has formed and subsequently transformed into a eutectoid microstructure in the cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by the diffusion-solution zone α’. If the diffusion-solution zone α’ is unsaturated, it will have much more crystal defects and the combination between α’ and phase P is weak, thus the process of phase boundary sliding becomes easily; on the