In this study,extrusion was performed on Mg-Zr-Sr-Dy alloys for improving their mechanical,corrosion,and biocompatibility properties.Effects of extrusion and alloying elements on the microstructural characteristics,te...In this study,extrusion was performed on Mg-Zr-Sr-Dy alloys for improving their mechanical,corrosion,and biocompatibility properties.Effects of extrusion and alloying elements on the microstructural characteristics,tensile and compressive strengths,corrosion behavior,and biocompatibility were investigated.The Mg-Zr-Sr-Dy alloys were composed of an α-Mg matrix containing {10■2} extension twins and secondary phases of intermetallic compounds Mg_(17)Sr_(2) and Mg_(2)Dy.Evolution of basal and rare earth(RE) textures was observed in the extruded alloys and an increase in Dy content to 2 wt.% resulted in texture randomization and strengthening of the RE component,mainly due to particle-stimulated nucleation and a change from discontinuous dynamic recrystallization to continuous dynamic recrystallization,which also led to an improved tension-compression yield asymmetry of 0.87.Extrusion of the alloys significantly enhanced their tensile and compressive properties due to improved distribution of alloying elements and formation of textures.Corrosion rates tested by hydrogen evolution testing,potentiodynamic polarization,and electrical impedance spectroscopy showed similar trends for each composition,and the lowest corrosion rate of 3.37 mmy^(-1) was observed for the Mg-1Zr-0.5Sr-1Dy in the potentiodynamic polarization testing.Dy_(2)O_(3) was observed in the inner layers of the Mg(OH)_(2) protective films,whose protective efficacy was confirmed by charge-transfer and film resistances.A comparison among the minimum CRs observed in this study and previously studied as-cast Mg-Zr-Sr-Dy and extruded Mg-Zr-Sr alloys,demonstrates that both the extrusion process and addition of Dy in Mg-Zr-Sr improved the CR.Similarly,extruded Mg-Zr-Sr-Dy alloys showed improved cell viability and adhesion of human osteoblast-like SaOS2 cells due to increased corrosion resistance and enhanced Sr distribution within the Mg matrix.展开更多
The NiA1 Cr（Mo） （Hf, Dy） hypoeutectic alloys were prepared by conventional casting and injection casting techniques respectively, and their microstructure and room temperature mechanical properties were investigat...The NiA1 Cr（Mo） （Hf, Dy） hypoeutectic alloys were prepared by conventional casting and injection casting techniques respectively, and their microstructure and room temperature mechanical properties were investigated. The results reveal that with the addition of Hf and Dy, the Ni2AIHf Heusler phase and NisDy phase form along the NiAI/Cr（Mo） phase boundaries in intercellular region. By the injection casting method, some Ni2AIHf Heusler phase and NisDy phase transform into Hf and Dy solid solutions, respectively. Moreover, the microstructure of the alloy gets good optimization, which can be characterized by the fine interlamellar spacing, high proportion of eutectic cell area and homogeneously distributed fine Ni2AIHf, NisDy, Hf solid solution and Dy solid solutions. Compared with conventional-cast alloy, the room temperature mechanical properties of injection-cast alloy are improved obviously.展开更多
Minor Dy element was added into a Mg?4Y?3Nd?0.4Zr alloy,and its effects on the microstructure and the mechanicalproperties at elevated temperatures were investigated.Scanning electron microscope(SEM)and transmission e...Minor Dy element was added into a Mg?4Y?3Nd?0.4Zr alloy,and its effects on the microstructure and the mechanicalproperties at elevated temperatures were investigated.Scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to observe the microstructures.The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg?REphases were Mg5RE and Mg3RE17,respectively,and distributed mainly along grain boundaries.After a solution treatment,theeutectic Mg5RE phases were dissolved into the matrix,whereas the Mg3RE17compound still remained.After peak aging,fineMg?RE phases were precipitated homogeneously within the matrix of the alloys containing Dy.Dy addition can result in asignificant improvement in the tensile strength at both room and elevated temperatures,and a slight decrease in the elongation.展开更多
Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by...Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by arc melting.Effect of Dy doping on the microstructure,magnetostrictive and mechanical properties of as-cast Fe83Ga17 alloy was investigated.Results show that Dy-doped alloys exhibit a dual-phase structure containing the A2 matrix and Dy-rich precipitates(Fe56Ga34Dy10).Both magnetostriction and mechanical properties of Fe83Ga17 alloys are improved by Dy doping.A small amount of Dy addition(x=0.2)significantly causes Fe83Ga17 alloy to transform from typical brittle material(fracture strainε<1%)to plastic material(ε≈11%).Correspondingly,the fracture mode transforms from intergranular fracture to dimple fracture.At the same time,the ultimate tensile strength and the magnetostriction rise up to 209 MPa and 64 ppm,respectively.Dy-rich precipitates disperse along the grain boundries and inside the grains,which plays an important role in the grain refinement and solution strengthening,and therefore,contribute to the enhancement of mechanical properties of the alloy.The improvement of magnetostriction could be attributed to the large lattice distortion induced by Dy atoms entering into the A2 matrix.Doping Dy into Fe-Ga alloys provides an effective solution to the brittleness in their applications.展开更多
The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts...The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts of monovalent cations. It was suggested that mono-valent cations had competition coordination with Na^+ for Dy(PPP)_2^(7-).展开更多
The composite of Dy-α-sialon/10 wt pct nano-size SiC particles has been prepared from precursor powders of Si3N4, AIN, Al2O3, Dy2O3 and nano-size β-SiC. The hardness, toughness and bending strength of the composite ...The composite of Dy-α-sialon/10 wt pct nano-size SiC particles has been prepared from precursor powders of Si3N4, AIN, Al2O3, Dy2O3 and nano-size β-SiC. The hardness, toughness and bending strength of the composite at ambient temperature are a little higher than those of Dy-α-sialon.while the bending strength is maintained up to 1000℃ and about 2 times more than that of Dy-α-sialon at the same temperature. The fracture surfaces show that the grain size of the composite is smaller than that of Dy-α-sialon, and both Of them have predominately transgranular mode of fracture. It is believed that the decrease of the bending strength of Dy-α-sialon at elevated temperature is caused by the viscous flow of the grain boundary phase, while the addition of nanosize SiC particles effectively increases the viscosity of the grain boundary phase and therefore prevents the strength loss of Dy-α-sialon/nano-size SiC composites at elevated temperature展开更多
基金the financial support for this research by the Australian Research Council (ARC) through the Future Fellowship (FT160100252)the Discovery Project (DP170102557)。
文摘In this study,extrusion was performed on Mg-Zr-Sr-Dy alloys for improving their mechanical,corrosion,and biocompatibility properties.Effects of extrusion and alloying elements on the microstructural characteristics,tensile and compressive strengths,corrosion behavior,and biocompatibility were investigated.The Mg-Zr-Sr-Dy alloys were composed of an α-Mg matrix containing {10■2} extension twins and secondary phases of intermetallic compounds Mg_(17)Sr_(2) and Mg_(2)Dy.Evolution of basal and rare earth(RE) textures was observed in the extruded alloys and an increase in Dy content to 2 wt.% resulted in texture randomization and strengthening of the RE component,mainly due to particle-stimulated nucleation and a change from discontinuous dynamic recrystallization to continuous dynamic recrystallization,which also led to an improved tension-compression yield asymmetry of 0.87.Extrusion of the alloys significantly enhanced their tensile and compressive properties due to improved distribution of alloying elements and formation of textures.Corrosion rates tested by hydrogen evolution testing,potentiodynamic polarization,and electrical impedance spectroscopy showed similar trends for each composition,and the lowest corrosion rate of 3.37 mmy^(-1) was observed for the Mg-1Zr-0.5Sr-1Dy in the potentiodynamic polarization testing.Dy_(2)O_(3) was observed in the inner layers of the Mg(OH)_(2) protective films,whose protective efficacy was confirmed by charge-transfer and film resistances.A comparison among the minimum CRs observed in this study and previously studied as-cast Mg-Zr-Sr-Dy and extruded Mg-Zr-Sr alloys,demonstrates that both the extrusion process and addition of Dy in Mg-Zr-Sr improved the CR.Similarly,extruded Mg-Zr-Sr-Dy alloys showed improved cell viability and adhesion of human osteoblast-like SaOS2 cells due to increased corrosion resistance and enhanced Sr distribution within the Mg matrix.
基金Project(2012M510271) supported by the China Postdoctoral Science FoundationProject(2012BAI18B05) supported by the Five-Year National Key Technology R&D Program during the 12th Five-year Plan of ChinaProject(2011AA030104) supported by the National High Technology Research and Development Program of China
文摘The NiA1 Cr（Mo） （Hf, Dy） hypoeutectic alloys were prepared by conventional casting and injection casting techniques respectively, and their microstructure and room temperature mechanical properties were investigated. The results reveal that with the addition of Hf and Dy, the Ni2AIHf Heusler phase and NisDy phase form along the NiAI/Cr（Mo） phase boundaries in intercellular region. By the injection casting method, some Ni2AIHf Heusler phase and NisDy phase transform into Hf and Dy solid solutions, respectively. Moreover, the microstructure of the alloy gets good optimization, which can be characterized by the fine interlamellar spacing, high proportion of eutectic cell area and homogeneously distributed fine Ni2AIHf, NisDy, Hf solid solution and Dy solid solutions. Compared with conventional-cast alloy, the room temperature mechanical properties of injection-cast alloy are improved obviously.
基金Project(GB09209)supported by the Science and Technology Bureau of Heilongjiang Province,China
文摘Minor Dy element was added into a Mg?4Y?3Nd?0.4Zr alloy,and its effects on the microstructure and the mechanicalproperties at elevated temperatures were investigated.Scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to observe the microstructures.The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg?REphases were Mg5RE and Mg3RE17,respectively,and distributed mainly along grain boundaries.After a solution treatment,theeutectic Mg5RE phases were dissolved into the matrix,whereas the Mg3RE17compound still remained.After peak aging,fineMg?RE phases were precipitated homogeneously within the matrix of the alloys containing Dy.Dy addition can result in asignificant improvement in the tensile strength at both room and elevated temperatures,and a slight decrease in the elongation.
基金Beijing Science and Technology Planning Project(Grant No.Z201100006720003)。
文摘Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by arc melting.Effect of Dy doping on the microstructure,magnetostrictive and mechanical properties of as-cast Fe83Ga17 alloy was investigated.Results show that Dy-doped alloys exhibit a dual-phase structure containing the A2 matrix and Dy-rich precipitates(Fe56Ga34Dy10).Both magnetostriction and mechanical properties of Fe83Ga17 alloys are improved by Dy doping.A small amount of Dy addition(x=0.2)significantly causes Fe83Ga17 alloy to transform from typical brittle material(fracture strainε<1%)to plastic material(ε≈11%).Correspondingly,the fracture mode transforms from intergranular fracture to dimple fracture.At the same time,the ultimate tensile strength and the magnetostriction rise up to 209 MPa and 64 ppm,respectively.Dy-rich precipitates disperse along the grain boundries and inside the grains,which plays an important role in the grain refinement and solution strengthening,and therefore,contribute to the enhancement of mechanical properties of the alloy.The improvement of magnetostriction could be attributed to the large lattice distortion induced by Dy atoms entering into the A2 matrix.Doping Dy into Fe-Ga alloys provides an effective solution to the brittleness in their applications.
文摘The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts of monovalent cations. It was suggested that mono-valent cations had competition coordination with Na^+ for Dy(PPP)_2^(7-).
文摘The composite of Dy-α-sialon/10 wt pct nano-size SiC particles has been prepared from precursor powders of Si3N4, AIN, Al2O3, Dy2O3 and nano-size β-SiC. The hardness, toughness and bending strength of the composite at ambient temperature are a little higher than those of Dy-α-sialon.while the bending strength is maintained up to 1000℃ and about 2 times more than that of Dy-α-sialon at the same temperature. The fracture surfaces show that the grain size of the composite is smaller than that of Dy-α-sialon, and both Of them have predominately transgranular mode of fracture. It is believed that the decrease of the bending strength of Dy-α-sialon at elevated temperature is caused by the viscous flow of the grain boundary phase, while the addition of nanosize SiC particles effectively increases the viscosity of the grain boundary phase and therefore prevents the strength loss of Dy-α-sialon/nano-size SiC composites at elevated temperature
