To further increase the mechanical properties, 0.5wt.% Sm was introduced to a Mg-10Y alloy in this study. The effects of Sm addition on the microstructures and mechanical properties of the Mg-10Y alloy, especially the...To further increase the mechanical properties, 0.5wt.% Sm was introduced to a Mg-10Y alloy in this study. The effects of Sm addition on the microstructures and mechanical properties of the Mg-10Y alloy, especially the aged Mg-10Y alloy, were investigated. The microstructure observation and tensile tests were performed by using an optical microscopy, a scanning electron microscopy and a universal material testing machine, respectively. The phase analysis was performed using X-ray diffractometer. The results show that the 0.5wt.% Sm addition can not only promote the formation of fine and dispersed Mg24Y5 phases, but also improve their morphology and distribution; it also increases the thermal stability of Mg24Y5 phases. Sm addition is seen to increase the ultimate tensile strength of Mg-10Y alloy at elevated temperatures(200, 250, 300 and 350 ℃), while decrease the elongation. But the elongation is still up to 7.5% even at 350 ℃. In the range of 250 ℃ to 300℃, the ultimate tensile strength of the alloy reaches its maximum(with a range average of 235 MPa) and is not sensitive to the temperature change, which is very useful to the application of heat-resistant magnesium alloys. Even at 350 ℃, the ultimate tensile strength of Mg-10Y-0.5Sm is still up to 155 MPa. Considering both of the ultimate tensile strength and elongation, the maximum application temperature of the Mg-10Y-0.5Sm alloy can be up to 300 ℃. The strengthening mechanisms of Mg-10Y-0.5Sm alloy are mainly attributed to dispersion strengthening of Mg24Y5 phase particles with a certain solubility of Sm and grain refinement strengthening of α-Mg matrix.展开更多
The effects of didymium(Nd : Pr = 3 : 1 )on the microstructure and mechanical properties of Mg-10%A1 alloy were studied with the additions of 0~3%Di. The small block-like Al2(Nd,Pr) phase appears in 1%Di alloy, the bl...The effects of didymium(Nd : Pr = 3 : 1 )on the microstructure and mechanical properties of Mg-10%A1 alloy were studied with the additions of 0~3%Di. The small block-like Al2(Nd,Pr) phase appears in 1%Di alloy, the blocklike Al2(Nd,Pr) and needle-like Al11(Nd,Pr)3 phases appear synchronously in 2%Di and 3%Di alloys, while the network of (Mg17Al12)βphase is broken up. The tensile properties can be improved with the addition of didymium. When the addition of didymium in Mg-10%A1 alloy reaches 2% , the alloy exhibits the best combination of strength and ductility, but the strength and ductility drop at the addition of 3% Di due to the obvious increase of the size and quantity of the needle-like Al11(Nd,Pr)3 phase.展开更多
The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5...The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.展开更多
The corrosion behaviors of a basic type of RE-containing magnesium alloy Mg-15Y processed by different heat treatment methods were studied in 3.5% NaC1 solution at room temperature. The amount of Mg24Y5 phase decrease...The corrosion behaviors of a basic type of RE-containing magnesium alloy Mg-15Y processed by different heat treatment methods were studied in 3.5% NaC1 solution at room temperature. The amount of Mg24Y5 phase decreased with the extending of homogenization treatment. The time for achieving dissolving equilibrium of homogenization treatment at 525, 535, and 545 ℃ was 24, 20, and 8 h, respectively. The corrosion behavior of Mg-15Y alloy was studied using immersion, hydrogen evolution and electrochemical tests. The experimental results revealed that the heat treatment improved the corrosion resistance, and the corrosion resistance became better with increasing the heat treatment time. The corrosion mode of the alloy after heat treatment was microgalvanic corrosion consisting of the cathodic Mg24Y5 phase and anodic α-Mg matrix, and Mg-15Y exhibited favorable uniform corrosion mode in NaC1 solution. The volume and increasing tendency of the homogenization treatment samples were both more than those of the as-cast sample.展开更多
The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2-5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffrac...The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2-5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffraction, transmission electron microscope and electron probe microanalysis. Experimental results show that the pressure has a great influence on the solidification microstructure of the Mg65Cu25Y10. At ambient pressure, the solidification products are Mg2(Cu,Y) and a very small amount of Y2O3 inclusion. As the pressure is above 2 GPa, a new Cu2(Y,Mg) phase appears, while Y2O3 is not observed at the pressure of 3, 4 and 5 GPa. When the pressure increases from 2 GPa to 5 GPa, the grain sizes of Mg2(Cu,Y) and Cu2(Y,Mg) decrease from 125, 96 nm to 80, 7 nm, respectively. The mechanisms for the effects of the pressure on the phase evolution and microstructure during solidification process of Mg65Cu25Y10 alloy have been discussed.展开更多
In this work,a new(Y,Gd)H_(2) precipitate was identified and systematically investigated in the as-cast Mg-6Gd-3Y-0.5Zr alloy by XRD,SEM with EDS,TEM with EDS techniques and thermodynamics analysis.Results show that t...In this work,a new(Y,Gd)H_(2) precipitate was identified and systematically investigated in the as-cast Mg-6Gd-3Y-0.5Zr alloy by XRD,SEM with EDS,TEM with EDS techniques and thermodynamics analysis.Results show that the as-cast alloy contains α-Mg,Mg_(24)(Gd,Y)_(5),and(Y,Gd)H_(2) phase.The(Y,Gd)H_(2) phase usually forms near the eutectic phase Mg_(24)(Gd,Y)_(5) or in the α-Mg grains,displaying a rectangle-shape.The Mg_(24)(Gd,Y)_(5) and(Y,Gd)H_(2) phases crystalize in bcc and fcc structure,respectively,and the(Y,Gd)H_(2) phase has a semi-coherent relationship with α-Mg matrix.The thermodynamics calculation results reveal that the hydrogen dissolved in the melt leads to the formation of hydrides.It is also found that the(Y,Gd)H_(2) hydride can form directly from the liquid phase during solidification.Additionally,it can precipitate by the decomposition of Mg_(24)(Gd,Y)_(5) phase due to absorbing hydrogen from the remaining melt.展开更多
The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). And, compression...The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). And, compression deformation behavior at room-temperature was studied. The results showed that the microstructure of Mg-8Zn-1Y alloy solidified under ambient pressure and super-high pressure was both mainly composed of ■-Mg and quasicrystal I-Mg3Zn6 Y. Solidification under super-high pressure contributed to refining solidified microstructure and changing morphology of the intergranular second phase. The morphology of intergranular second phase(quasicrystal I-Mg3Zn6Y) was transformed from continuous network(ambient pressure) to long island(high pressure) and finally to granular(super-high pressure) with the increase in pressure. The compressive strength, yield strength and rupture strain of the samples solidified under ambient pressure were significantly improved from 262.6 MPa, 244.4 MPa and 13.3% to 437.3 MPa, 368.9 MPa and 24.7% under the pressure of 6 GPa, respectively. Under ambient pressure, cleavage plane on compressive fracture was large and smooth. When it was solidified under the pressure ranging from 4 to 6 GPa, cleavage plane on compressive fracture was small and coarse. In addition, dimple, tear ridge and lobate patterns existed.展开更多
Double-pass hot compression tests were carried out over a wide range of holding time(0–180 s) and Zener-Hollomon parameter(1.6 E15–1.3 E20) to study the deformation behavior of cast Mg-8 Gd-3 Y alloy.The flow cu...Double-pass hot compression tests were carried out over a wide range of holding time(0–180 s) and Zener-Hollomon parameter(1.6 E15–1.3 E20) to study the deformation behavior of cast Mg-8 Gd-3 Y alloy.The flow curves show obvious work hardening and strain softening stages, leading to the peak stress of double-pass hot compression. Holding time and Zener-Hollomon parameter can significantly affect the second pass peak stress. It is found that increasing the holding time can cause a higher peak stress in the second pass deformation. The second pass stress reaches the peak stress of 71 MPa at ZenerHollomom parameter of 1.6 E15. When the parameter rises to 1.3 E20, the second pass peak goes up to237 MPa. In addition, the second pass peak stress is significantly higher than the unloading stress, which is opposite to the flow behavior of aluminum alloys. Residual stored deformation energy caused by the first pass deformation could be consumed by metadynamic recrystallization. Therefore, more strain energy is required for subsequent dynamic recrystallization, resulting in hardening behavior. A hardening fraction is defined to describe the deformation behavior quantitatively, which shows a positive correlation with the metadynamic recrystallization fraction. The metadynamic recrystallization leads to grain growth at the inter pass holding stage, diminishing dynamic recrystallization nucleation positions in the second pass deformation.展开更多
The microstructure evolution and mechanical properties of Mg-15Gd-3Y alloy were investigated in the as-cast and heat treated conditions. The microstrucmre evolution from as-cast to cast-T4 states involved a-Mg solid s...The microstructure evolution and mechanical properties of Mg-15Gd-3Y alloy were investigated in the as-cast and heat treated conditions. The microstrucmre evolution from as-cast to cast-T4 states involved a-Mg solid solution+Mg5(Gd,Y) phase→a-Mg supersaturated solid solution+rare earths compound Mg3(Gdl.26,Y0.74)→a-Mg supersaturated solid solution+rare earths compound Mg3(Gd0.Tas,Y1.255). It showed that 480 ℃/4 h was the optimal solution treatment parameter. If the solution temperature was high or the holding time was long, such as 520 ℃/16 h, an overheating phenomenon would be induced, which had a detrimental effect on the mechanical properties. When ageing at 225 and 200℃, the alloy would exhibit a significant age-hardening response and great long-time-age-hardening potential, respectively. The best mechanical properties were obtained at the parameters of 480 ℃/4 h+225 ℃/16 h, with the UTS of 257.0 MPa and elongation of 3.8%.展开更多
The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The resu...The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The results indicated that the corrosion resistance of Mg-15Y sample gradually deteriorated with immersion time increasing, which was consistent with the observation of corrosion morphologies. The solid-solution treatment decreased the amounts of second phase Mg24Ys. The Ecor~ and corrosion rate of as-cast samples were both lower than those of solid solution-treated samples, and both increased with increment of solid solution-treated time. The corrosion mechanism was proposed for the galvanic, pitting and filiform corrosion which varied with the immersion time and solid-solution treatment.展开更多
In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron micros...In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), energy dispersive spectrum(EDS) and tensile testing.The results indicated that the microstructure was obviously refined by extrusion and dynamic recrystallization.The second phases were dynamic precipitated and distributed more dispersively through extrusion.W-Phases(Mg3Zn3Y2) were twisted and broken, while I-Phases(Mg3Zn6Y) were spheroidized by deformation.Twin bands were formed to achieve the large deformation and hinder the slip of dislocations effectively to improve tensile properties.The tensile strength and elongation of extruded Mg-4Zn-1Y alloy were 254.94 MPa and 17.9% respectively which were improved greatly compared with those of as-cast alloy.The strengthening mechanisms of the extruded alloy were mainly fine-grain strengthening and distortion strengthening.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51171059)the Innovative Research Team(in Science and Technology)in University of Henan Province(No.2012IRTSTHN008)the Basic and Frontier Technologies Research Plan of Henan Province(No.102300410018)
文摘To further increase the mechanical properties, 0.5wt.% Sm was introduced to a Mg-10Y alloy in this study. The effects of Sm addition on the microstructures and mechanical properties of the Mg-10Y alloy, especially the aged Mg-10Y alloy, were investigated. The microstructure observation and tensile tests were performed by using an optical microscopy, a scanning electron microscopy and a universal material testing machine, respectively. The phase analysis was performed using X-ray diffractometer. The results show that the 0.5wt.% Sm addition can not only promote the formation of fine and dispersed Mg24Y5 phases, but also improve their morphology and distribution; it also increases the thermal stability of Mg24Y5 phases. Sm addition is seen to increase the ultimate tensile strength of Mg-10Y alloy at elevated temperatures(200, 250, 300 and 350 ℃), while decrease the elongation. But the elongation is still up to 7.5% even at 350 ℃. In the range of 250 ℃ to 300℃, the ultimate tensile strength of the alloy reaches its maximum(with a range average of 235 MPa) and is not sensitive to the temperature change, which is very useful to the application of heat-resistant magnesium alloys. Even at 350 ℃, the ultimate tensile strength of Mg-10Y-0.5Sm is still up to 155 MPa. Considering both of the ultimate tensile strength and elongation, the maximum application temperature of the Mg-10Y-0.5Sm alloy can be up to 300 ℃. The strengthening mechanisms of Mg-10Y-0.5Sm alloy are mainly attributed to dispersion strengthening of Mg24Y5 phase particles with a certain solubility of Sm and grain refinement strengthening of α-Mg matrix.
基金Project supported by the Science & Technology Bureau of Sichuan Province of China (04GG1589)
文摘The effects of didymium(Nd : Pr = 3 : 1 )on the microstructure and mechanical properties of Mg-10%A1 alloy were studied with the additions of 0~3%Di. The small block-like Al2(Nd,Pr) phase appears in 1%Di alloy, the blocklike Al2(Nd,Pr) and needle-like Al11(Nd,Pr)3 phases appear synchronously in 2%Di and 3%Di alloys, while the network of (Mg17Al12)βphase is broken up. The tensile properties can be improved with the addition of didymium. When the addition of didymium in Mg-10%A1 alloy reaches 2% , the alloy exhibits the best combination of strength and ductility, but the strength and ductility drop at the addition of 3% Di due to the obvious increase of the size and quantity of the needle-like Al11(Nd,Pr)3 phase.
基金the financial support by the Natioal Natural Science Foundation of China(Nos.:51571086 and 51271073)the financial support from the Natural Science Foundation of Henan Polytechnic University(No.:B2010-20)。
文摘The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.
基金Funded by the National Key Technology R&D Program of China
文摘The corrosion behaviors of a basic type of RE-containing magnesium alloy Mg-15Y processed by different heat treatment methods were studied in 3.5% NaC1 solution at room temperature. The amount of Mg24Y5 phase decreased with the extending of homogenization treatment. The time for achieving dissolving equilibrium of homogenization treatment at 525, 535, and 545 ℃ was 24, 20, and 8 h, respectively. The corrosion behavior of Mg-15Y alloy was studied using immersion, hydrogen evolution and electrochemical tests. The experimental results revealed that the heat treatment improved the corrosion resistance, and the corrosion resistance became better with increasing the heat treatment time. The corrosion mode of the alloy after heat treatment was microgalvanic corrosion consisting of the cathodic Mg24Y5 phase and anodic α-Mg matrix, and Mg-15Y exhibited favorable uniform corrosion mode in NaC1 solution. The volume and increasing tendency of the homogenization treatment samples were both more than those of the as-cast sample.
基金supported by the National Natural Science Foundation of China(Grant number:50071060)the National Development Project for Basic Scientific Research(Grant number:G2000067201).
文摘The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2-5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffraction, transmission electron microscope and electron probe microanalysis. Experimental results show that the pressure has a great influence on the solidification microstructure of the Mg65Cu25Y10. At ambient pressure, the solidification products are Mg2(Cu,Y) and a very small amount of Y2O3 inclusion. As the pressure is above 2 GPa, a new Cu2(Y,Mg) phase appears, while Y2O3 is not observed at the pressure of 3, 4 and 5 GPa. When the pressure increases from 2 GPa to 5 GPa, the grain sizes of Mg2(Cu,Y) and Cu2(Y,Mg) decrease from 125, 96 nm to 80, 7 nm, respectively. The mechanisms for the effects of the pressure on the phase evolution and microstructure during solidification process of Mg65Cu25Y10 alloy have been discussed.
基金financially supported by the Key Project of Equipment Pre-research Field Fund under Grant No.61409230407the National Natural Science Foundation of China(NSFC)under Grant No.51601054the Central Government Guides Local Science and Technology Development Fund Projects under Grant No.206Z1005G。
文摘In this work,a new(Y,Gd)H_(2) precipitate was identified and systematically investigated in the as-cast Mg-6Gd-3Y-0.5Zr alloy by XRD,SEM with EDS,TEM with EDS techniques and thermodynamics analysis.Results show that the as-cast alloy contains α-Mg,Mg_(24)(Gd,Y)_(5),and(Y,Gd)H_(2) phase.The(Y,Gd)H_(2) phase usually forms near the eutectic phase Mg_(24)(Gd,Y)_(5) or in the α-Mg grains,displaying a rectangle-shape.The Mg_(24)(Gd,Y)_(5) and(Y,Gd)H_(2) phases crystalize in bcc and fcc structure,respectively,and the(Y,Gd)H_(2) phase has a semi-coherent relationship with α-Mg matrix.The thermodynamics calculation results reveal that the hydrogen dissolved in the melt leads to the formation of hydrides.It is also found that the(Y,Gd)H_(2) hydride can form directly from the liquid phase during solidification.Additionally,it can precipitate by the decomposition of Mg_(24)(Gd,Y)_(5) phase due to absorbing hydrogen from the remaining melt.
基金Project(2007CB613701)supported by the National Basic Research Program of ChinaProject(20100470125)by National Science Foundation for Post-doctoral Scientists of ChinaProject(2009021028)supported by Science and Technique Foundation for Young Scholars of Shanxi Province
基金Project supported by National Natural Science Foundation of China(51475486)Natural Science Foundation of Hebei Province(E2013501096)
文摘The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). And, compression deformation behavior at room-temperature was studied. The results showed that the microstructure of Mg-8Zn-1Y alloy solidified under ambient pressure and super-high pressure was both mainly composed of ■-Mg and quasicrystal I-Mg3Zn6 Y. Solidification under super-high pressure contributed to refining solidified microstructure and changing morphology of the intergranular second phase. The morphology of intergranular second phase(quasicrystal I-Mg3Zn6Y) was transformed from continuous network(ambient pressure) to long island(high pressure) and finally to granular(super-high pressure) with the increase in pressure. The compressive strength, yield strength and rupture strain of the samples solidified under ambient pressure were significantly improved from 262.6 MPa, 244.4 MPa and 13.3% to 437.3 MPa, 368.9 MPa and 24.7% under the pressure of 6 GPa, respectively. Under ambient pressure, cleavage plane on compressive fracture was large and smooth. When it was solidified under the pressure ranging from 4 to 6 GPa, cleavage plane on compressive fracture was small and coarse. In addition, dimple, tear ridge and lobate patterns existed.
基金support of the National Key Research and Development Program of China (Grant No. 2016YFB0301103 and No. 2016YFB0101604)the National Natural Science Foundation of China (Grant No. 51601112)the Shanghai Rising-Star Program (Grant No. 17QB1403000)
文摘Double-pass hot compression tests were carried out over a wide range of holding time(0–180 s) and Zener-Hollomon parameter(1.6 E15–1.3 E20) to study the deformation behavior of cast Mg-8 Gd-3 Y alloy.The flow curves show obvious work hardening and strain softening stages, leading to the peak stress of double-pass hot compression. Holding time and Zener-Hollomon parameter can significantly affect the second pass peak stress. It is found that increasing the holding time can cause a higher peak stress in the second pass deformation. The second pass stress reaches the peak stress of 71 MPa at ZenerHollomom parameter of 1.6 E15. When the parameter rises to 1.3 E20, the second pass peak goes up to237 MPa. In addition, the second pass peak stress is significantly higher than the unloading stress, which is opposite to the flow behavior of aluminum alloys. Residual stored deformation energy caused by the first pass deformation could be consumed by metadynamic recrystallization. Therefore, more strain energy is required for subsequent dynamic recrystallization, resulting in hardening behavior. A hardening fraction is defined to describe the deformation behavior quantitatively, which shows a positive correlation with the metadynamic recrystallization fraction. The metadynamic recrystallization leads to grain growth at the inter pass holding stage, diminishing dynamic recrystallization nucleation positions in the second pass deformation.
基金Project supported by the National Natural Science Foundation of China (50775085)Special Fund for Basic Research and Operating Expenses of Central College (M2009061)Natural Science Foundation of Ningbo City(2008A610049)
文摘The microstructure evolution and mechanical properties of Mg-15Gd-3Y alloy were investigated in the as-cast and heat treated conditions. The microstrucmre evolution from as-cast to cast-T4 states involved a-Mg solid solution+Mg5(Gd,Y) phase→a-Mg supersaturated solid solution+rare earths compound Mg3(Gdl.26,Y0.74)→a-Mg supersaturated solid solution+rare earths compound Mg3(Gd0.Tas,Y1.255). It showed that 480 ℃/4 h was the optimal solution treatment parameter. If the solution temperature was high or the holding time was long, such as 520 ℃/16 h, an overheating phenomenon would be induced, which had a detrimental effect on the mechanical properties. When ageing at 225 and 200℃, the alloy would exhibit a significant age-hardening response and great long-time-age-hardening potential, respectively. The best mechanical properties were obtained at the parameters of 480 ℃/4 h+225 ℃/16 h, with the UTS of 257.0 MPa and elongation of 3.8%.
基金supported by the National Key Technology R&D Program of China (2011BAE22B01)
文摘The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The results indicated that the corrosion resistance of Mg-15Y sample gradually deteriorated with immersion time increasing, which was consistent with the observation of corrosion morphologies. The solid-solution treatment decreased the amounts of second phase Mg24Ys. The Ecor~ and corrosion rate of as-cast samples were both lower than those of solid solution-treated samples, and both increased with increment of solid solution-treated time. The corrosion mechanism was proposed for the galvanic, pitting and filiform corrosion which varied with the immersion time and solid-solution treatment.
基金Project supported by General Program of Liaoning Province Committee of Education(L2012035)Liaoning Province Science and Technology Plan(2013201018)Liaoning Province University Innovation Team Support Plan
文摘In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), energy dispersive spectrum(EDS) and tensile testing.The results indicated that the microstructure was obviously refined by extrusion and dynamic recrystallization.The second phases were dynamic precipitated and distributed more dispersively through extrusion.W-Phases(Mg3Zn3Y2) were twisted and broken, while I-Phases(Mg3Zn6Y) were spheroidized by deformation.Twin bands were formed to achieve the large deformation and hinder the slip of dislocations effectively to improve tensile properties.The tensile strength and elongation of extruded Mg-4Zn-1Y alloy were 254.94 MPa and 17.9% respectively which were improved greatly compared with those of as-cast alloy.The strengthening mechanisms of the extruded alloy were mainly fine-grain strengthening and distortion strengthening.