The effects of silicocalcium on the microstructure and mechanical properties of casting magnesium alloy Mg-6Al-0.5Mn(AM60) were studied. The results show that the microstructure of AM60 casting magnesium alloy is effe...The effects of silicocalcium on the microstructure and mechanical properties of casting magnesium alloy Mg-6Al-0.5Mn(AM60) were studied. The results show that the microstructure of AM60 casting magnesium alloy is effectively refined by adding small amount of silicocalcium. The grain size decreases from 180 μm to 80 μm with 1.8% Si addition, while the size increases with 2.5% Si addition. The AM60+Si-Ca alloys mainly contain Mg matrix, β-Mg17Al12 phase, Al8Mn5 phase and a small polygonal type Mg2Si phase in matrix. Al8Mn5 can act as the heterogeneous nucleation for the Mg2Si phase. With the increase of silicocalcium, the content of Mg2Si phase increases gradually, the Mg2Si particles grow up and change coarse gradually. The microhardness of AM60 matrix increases with silicocalcium addition. The peak values of the tensile strength, elongation and impact toughness appear simultaneously with 1.8% silicocalcium addition, and the tensile strength, elongation and impact toughness are heightened respectively by 13.9%, 28.5% and 100%.展开更多
The effects of Ce addition on the microstructure of Mg-6Zn-1Mn alloy during casting, homogenization, hot extrusion, T4, T6 and T4＋two-step aging were investigated. The mechanical properties of alloys with and without...The effects of Ce addition on the microstructure of Mg-6Zn-1Mn alloy during casting, homogenization, hot extrusion, T4, T6 and T4＋two-step aging were investigated. The mechanical properties of alloys with and without Ce were compared. The results showed that Ce had an obvious effect on the microstructure of ZM61-0.5Ce alloy by restricting the occurrence of dynamic recrystallization and restraining the grain growth during extrusion and heat treatment subsequently. A new binary phase Mg 12 Ce was identified in ZM61-0.5Ce alloy, which distributed at grain boundaries and was broken to small particles distributed at grain boundaries along extrusion direction during extrusion. The mechanical properties of as-extruded ZM61-0.5Ce alloy were improved with the addition of Ce. The improved tensile properties of as-extruded ZM61-0.5Ce alloy were due to the finer grain sizes as compared to ZM61 alloy. However, the UTS and YS decreased severely and the elongation increased when ZM61-0.5Ce was treated by T6 and T4＋two-step aging. Brittle Mg 12 Ce phase, which was distributed at the grain boundary areas and cannot dissolve into the Mg matrix after solution treatment, became crack source under tensile stress.展开更多
The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500machine over deformation temperature range of300-450℃and strain rate of0.01-10s^-1.The mic...The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500machine over deformation temperature range of300-450℃and strain rate of0.01-10s^-1.The microstructural evolution of the alloy during the hot compression process was characterized by transmission electron microscopy(TEM)and electron back scatter diffractometry(EBSD).The results show that the flow stress behavior and microstructural evolution are sensitive to deformation parameters.The peak stress level,steady flow stress,dislocation density and amount of substructures of the alloy increase with decreasing deformation temperature and increasing strain rate.Conversely,the high angle grain boundary area increases,the grain boundary is in serrated shape and the dynamic recrystallization in the alloy occurs.The microstructure of the alloy is fibrous-like and the main softening mechanism is dynamic recovery during steady deformation state.The flow stress behavior can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of184.2538kJ/mol.The constitutive equation and the hot processing map were established.The hot processing map exhibits that the optimum processing conditions for Al-9Mg-1.1Li-0.5Mn alloy are in deformation temperature range from380to450℃and strain rate range from0.01to0.1s^-1.展开更多
Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr ...Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.展开更多
A new rare earth magnesium alloy(Mg-6 Zn-4 Sm-0.4 Zr, wt.%) was prepared by permanent mould casting. The microstructure and mechanical properties of the alloy sample in as-cast and various heat treatment situations we...A new rare earth magnesium alloy(Mg-6 Zn-4 Sm-0.4 Zr, wt.%) was prepared by permanent mould casting. The microstructure and mechanical properties of the alloy sample in as-cast and various heat treatment situations were characterized with an optical microscope(OM), X-ray diffractometer(XRD), scanning electron microscope(SEM) equipped with energy dispersive spectroscope(EDS), transmission electron microscope(TEM) and mechanical tests at room temperature, respectively. The experimental results show that the as-cast alloy mainly consists of α-Mg, eutectic Mg_2Zn_3, MgZnSm and Mg_(41)Sm_5. These eutectic phases with continuous or semicontinuous morphology principally distribute along grain boundaries. Almost all the eutectic compounds dissolve in α-Mg and the grains have no obvious growth trend after optimum solution treatment at 490 °C for 18 h. Meanwhile, the ultimate tensile strength(UTS) of 229 MPa and elongation(EL) to rupture of 9.78% can be achieved through the optimal solution treatment, which increase by 37 MPa and 57.74%, respectively, compared with that of the as-cast alloy. Further aging treatments at 200 °C for different durations lead to the conspicuous increment of mechanical properties and prominent age-hardening response. Peak-aged alloy(treated at 200 °C for 12 h) reveals better mechanical properties(UTS 258 MPa, EL 9.42%, hardness 73.4 HV) compared with the same alloy treated in other aging conditions, which is mainly ascribed to precipitated Mg_2Zn_3 and MgZn_2 phases. Fracture analysis demonstrates that the as-cast alloy belongs to inter-granular and cleavage fracture patterns, while the solutionized alloy(treated at 490 °C for 18 h) reveals trans-granular and quasi-cleavage fracture modes. For the peak-aged alloy, the fracture pattern obeys the mixture of trans-granular and cleavage modes.展开更多
The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A d...The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.展开更多
Mg-6 Al-1 Zn-xFe（x = 0,1,3,5 and 7 wt%）alloys were prepared by powder metallurgy and followed by hot extrusion.Majority of Fe element exists as insoluble particles in the alloys.The as-extruded alloys showed higher ...Mg-6 Al-1 Zn-xFe（x = 0,1,3,5 and 7 wt%）alloys were prepared by powder metallurgy and followed by hot extrusion.Majority of Fe element exists as insoluble particles in the alloys.The as-extruded alloys showed higher degradable rates but less stable mechanical properties than as-annealed alloys.Corrosion rate of all the alloys increased with increasing Fe concentration,reaching 2.4 mL cm-2h-1.0.2% yield strength of all the alloys was higher than 150 MPa.In short,Mg-6 Al-1 Zn-xFe alloys have an attractive combination of corrosion and mechanical properties,which holds a bright future for fracturing balls applications.展开更多
基金Project(204085) supported by the Key Project of Education Ministry of China Project(0523020500) supported by the Key Scientific and Technical Projects of Henan Province
文摘The effects of silicocalcium on the microstructure and mechanical properties of casting magnesium alloy Mg-6Al-0.5Mn(AM60) were studied. The results show that the microstructure of AM60 casting magnesium alloy is effectively refined by adding small amount of silicocalcium. The grain size decreases from 180 μm to 80 μm with 1.8% Si addition, while the size increases with 2.5% Si addition. The AM60+Si-Ca alloys mainly contain Mg matrix, β-Mg17Al12 phase, Al8Mn5 phase and a small polygonal type Mg2Si phase in matrix. Al8Mn5 can act as the heterogeneous nucleation for the Mg2Si phase. With the increase of silicocalcium, the content of Mg2Si phase increases gradually, the Mg2Si particles grow up and change coarse gradually. The microhardness of AM60 matrix increases with silicocalcium addition. The peak values of the tensile strength, elongation and impact toughness appear simultaneously with 1.8% silicocalcium addition, and the tensile strength, elongation and impact toughness are heightened respectively by 13.9%, 28.5% and 100%.
基金Project(2007CB613700)supported by the National Basic Research Program of ChinaProject(2007BAG06B04)supported by the National Key Technology R&D Program+2 种基金Project(CSTC,2009AB4008)supported by the Chongqing Sci&Tech ProgramProject(50725413)supported by the National Natural Science Foundation of ChinaProject(CDJXS10132202)supported by the Fundamental Research Funds for the Central Universities, China
文摘The effects of Ce addition on the microstructure of Mg-6Zn-1Mn alloy during casting, homogenization, hot extrusion, T4, T6 and T4＋two-step aging were investigated. The mechanical properties of alloys with and without Ce were compared. The results showed that Ce had an obvious effect on the microstructure of ZM61-0.5Ce alloy by restricting the occurrence of dynamic recrystallization and restraining the grain growth during extrusion and heat treatment subsequently. A new binary phase Mg 12 Ce was identified in ZM61-0.5Ce alloy, which distributed at grain boundaries and was broken to small particles distributed at grain boundaries along extrusion direction during extrusion. The mechanical properties of as-extruded ZM61-0.5Ce alloy were improved with the addition of Ce. The improved tensile properties of as-extruded ZM61-0.5Ce alloy were due to the finer grain sizes as compared to ZM61 alloy. However, the UTS and YS decreased severely and the elongation increased when ZM61-0.5Ce was treated by T6 and T4＋two-step aging. Brittle Mg 12 Ce phase, which was distributed at the grain boundary areas and cannot dissolve into the Mg matrix after solution treatment, became crack source under tensile stress.
基金Project (2017JJ2073) supported by the Natural Science Foundation of Hunan Province,China
文摘The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500machine over deformation temperature range of300-450℃and strain rate of0.01-10s^-1.The microstructural evolution of the alloy during the hot compression process was characterized by transmission electron microscopy(TEM)and electron back scatter diffractometry(EBSD).The results show that the flow stress behavior and microstructural evolution are sensitive to deformation parameters.The peak stress level,steady flow stress,dislocation density and amount of substructures of the alloy increase with decreasing deformation temperature and increasing strain rate.Conversely,the high angle grain boundary area increases,the grain boundary is in serrated shape and the dynamic recrystallization in the alloy occurs.The microstructure of the alloy is fibrous-like and the main softening mechanism is dynamic recovery during steady deformation state.The flow stress behavior can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of184.2538kJ/mol.The constitutive equation and the hot processing map were established.The hot processing map exhibits that the optimum processing conditions for Al-9Mg-1.1Li-0.5Mn alloy are in deformation temperature range from380to450℃and strain rate range from0.01to0.1s^-1.
基金Project(51975167) supported by the National Natural Science Foundation,China。
文摘Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.
基金financially supported by the National Nature Science Foundations of China(51464032)National Basic Research Program of China(Grant No.2010CB635106)
文摘A new rare earth magnesium alloy(Mg-6 Zn-4 Sm-0.4 Zr, wt.%) was prepared by permanent mould casting. The microstructure and mechanical properties of the alloy sample in as-cast and various heat treatment situations were characterized with an optical microscope(OM), X-ray diffractometer(XRD), scanning electron microscope(SEM) equipped with energy dispersive spectroscope(EDS), transmission electron microscope(TEM) and mechanical tests at room temperature, respectively. The experimental results show that the as-cast alloy mainly consists of α-Mg, eutectic Mg_2Zn_3, MgZnSm and Mg_(41)Sm_5. These eutectic phases with continuous or semicontinuous morphology principally distribute along grain boundaries. Almost all the eutectic compounds dissolve in α-Mg and the grains have no obvious growth trend after optimum solution treatment at 490 °C for 18 h. Meanwhile, the ultimate tensile strength(UTS) of 229 MPa and elongation(EL) to rupture of 9.78% can be achieved through the optimal solution treatment, which increase by 37 MPa and 57.74%, respectively, compared with that of the as-cast alloy. Further aging treatments at 200 °C for different durations lead to the conspicuous increment of mechanical properties and prominent age-hardening response. Peak-aged alloy(treated at 200 °C for 12 h) reveals better mechanical properties(UTS 258 MPa, EL 9.42%, hardness 73.4 HV) compared with the same alloy treated in other aging conditions, which is mainly ascribed to precipitated Mg_2Zn_3 and MgZn_2 phases. Fracture analysis demonstrates that the as-cast alloy belongs to inter-granular and cleavage fracture patterns, while the solutionized alloy(treated at 490 °C for 18 h) reveals trans-granular and quasi-cleavage fracture modes. For the peak-aged alloy, the fracture pattern obeys the mixture of trans-granular and cleavage modes.
基金Project(51141007)supported by the National Natural Science Foundation of ChinaProject(E2013501096)supported by Hebei Province Natural Science Foundation,China
文摘The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.
基金supported by project of the National Natural Science Foundation of China (51671041, 51701029 and 51531002)the National Key Research and Development Program of China (2016YFB0301100)+2 种基金the Fundamental Research Funds for the Central Universities (106112016CDJXZ138811 and 2018CDGFCL005)the China Postdoctoral Science Foundation Funded Project (2017M620410 and 2018T110942)the Chongqing Postdoctoral Scientific Research Foundation (Xm2017010)
文摘Mg-6 Al-1 Zn-xFe（x = 0,1,3,5 and 7 wt%）alloys were prepared by powder metallurgy and followed by hot extrusion.Majority of Fe element exists as insoluble particles in the alloys.The as-extruded alloys showed higher degradable rates but less stable mechanical properties than as-annealed alloys.Corrosion rate of all the alloys increased with increasing Fe concentration,reaching 2.4 mL cm-2h-1.0.2% yield strength of all the alloys was higher than 150 MPa.In short,Mg-6 Al-1 Zn-xFe alloys have an attractive combination of corrosion and mechanical properties,which holds a bright future for fracturing balls applications.
