The effects of Y on the microstructure and mechanical properties of Mg-6Zn-lMn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mecha...The effects of Y on the microstructure and mechanical properties of Mg-6Zn-lMn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mechanical properties of Mg-6Zn-lMn alloy. Varied phases compositions, including Mg7Zn3, I-phase (Mg3YZn6), W-phase (Mg3Y2Zn3) and X-phase (MgI2YZn), are obtained by adjusting the Zn to Y mass ratio. Mn element exists as the fine Mn particles, which are well distributed in the alloy. Thermal analysis and microstructure observation reveal that the phase stability follows the trend of X〉W〉/〉MgTZn3. In addition, Y can improve the mechanical properties of Mg-Zn-Mn alloy significantly, and the alloy with Y content of 6.09% has the best mechanical properties. The high strength is mainly due to the strengthening by the grain size refinement, dispersion strengthening by fine Mn particles, and introduction of the Mg-Zn-Y ternary phases.展开更多
The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explain...The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explained from the ternary phase diagram calculation. The results show that the formation of the secondary phases in Mg-Zn-Y-Zr alloys firmly depends on the mole ratio of Y to Zn, and X (Mg 12 YZn)-phase, W (Mg 3 Y 2 Zn 3 )-phase and I (Mg 3 YZn 6 )-phase come out in sequence as the ratio of Y to Zn decreases. The mole ratios of Y to Zn with the corresponding phase constituent are suggested quantitatively as follows: the phase constituent is α-Mg + I when the mole ratio of Y to Zn is about 0.164; α-Mg + I +W when the mole ratio of Y to Zn is in the range of 0.164 0.33;α-Mg +W when the mole ratio of Y to Zn is about 0.33; α-Mg +W+X when the mole ratio of Y to Zn is in the range of 0.33 1.32; and α-Mg +X when the mole ratio of Y to Zn is about 1.32. The results also offer a guideline for alloy selection and alloy design in Mg-Zn-Y-Zr system.展开更多
Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were...Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were correspondingly investigated. The results indicate that the Mg element is homogeneously distributed in the matrix and the fragmentized Cu2Te phase is dispersed in the matrix after hot rolling. Then, the Cu2Te phase is further stretched to strip shape after the cold rolling process. The microstructures of the cold-rolled alloy keep unchanged for the sample annealed below 390 ℃ for 1 h. However, after annealing at 550 ℃ for 1 h, the copper alloy with fibrous microstructures formed during the cold rolling process recrystallizes, leading to an obvious drop of hardening effect and an increase of electrical conductivity. The Cu-Mg-Te-Y alloy with better comprehensive properties is obtained by annealing at 360-390 ℃.展开更多
The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn and Mg-6Zn-1Mn-4Sn-0.5Y alloys under extrusion and T6 aging conditions were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning ...The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn and Mg-6Zn-1Mn-4Sn-0.5Y alloys under extrusion and T6 aging conditions were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM) and tensile test. The results show that Y element refines the grains and improves the comprehensive mechanical properties of ZMT614-0.5Y both in as-extruded and T6 states. The phase compositions of Mg-6Zn-1Mn-4Sn-0.5Y are α-Mg, Mg Zn2, Mn, Mg2 Sn and Mg Sn Y phases. After T6 treatment, the ultimate tensile strength(UTS) and yield strength(YS) increase while the elongation decreases severely. For both of these alloys, the theoretical results combined with the experimental values demonstrate that the grain boundary strengthening and solid solution strengthening play an important role in enhancing the YS in the as-extruded state, while the precipitation strengthening is the key factor for the enhancement of YS in the T6 state.展开更多
In order to improve the high temperature oxidation resistance of TiAl alloy, Y modified silicide coatings were prepared by pack cementation process at 1030, 1080 and 1130 °C, respectively, for 5 h. The microstruc...In order to improve the high temperature oxidation resistance of TiAl alloy, Y modified silicide coatings were prepared by pack cementation process at 1030, 1080 and 1130 °C, respectively, for 5 h. The microstructures, phase constitutions and oxidation behavior of these coatings were studied. The results show that the coating prepared by co-depositing Si?Y at 1080 °C for 5 h has a multiple layer structure: a superficial zone consisting of Al-rich (Ti,Nb)5Si4 and (Ti,Nb)5Si3, an out layer consisting of (Ti,Nb)Si2, a middle layer consisting of (Ti,Nb)5Si4 and (Ti,Nb)5Si3, and aγ-TiAl inner layer. Co-deposition temperature imposes strong influences on the coating structure. The coating prepared by Si?Y co-depositing at 1080 °C for 5 h shows relatively good oxidation resistance at 1000 °C in air, and the oxidation rate constant of the coating is about two orders of magnitude lower than that of the bare TiAl alloy.展开更多
A high strength GW94 alloy with fully recrystallized microstructure and equiaxed ultrafine grains of submicron size was produced by multiaxial forging and ageing. The alloy exhibits an ultimate tensile strength of 377...A high strength GW94 alloy with fully recrystallized microstructure and equiaxed ultrafine grains of submicron size was produced by multiaxial forging and ageing. The alloy exhibits an ultimate tensile strength of 377 MPa, proof stress of 295 MPa and elongation to failure of 21.7%. The ductility is improved in comparison with that of the conventional extrusion processing. Superplastic ductility is achieved in tensile testing at 573 K with a maximum elongation of 450%. These high ductility and high strength are attributed to the coexistence of fully recrystallized grains and nanoscale Mg 5 (Gd, Y) particles dynamically precipitated at grain boundaries.展开更多
The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly com...The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly composed ofα-Mg, Mg2Ca, Ca2Mg6Zn3,I (Mg3YZn6) andW (Mg3Y2Zn3) phases. However, with Y content increasing from 0.86% to 2.68%, the amount of the Ca2Mg6Zn3 phase gradually decreases but that of theI (Mg3YZn6) andW (Mg3Y2Zn3) phases gradually increases. Furthermore, an increase in Y content from 0.86% to 2.68% also causes the grain size of the as-cast alloys to gradually decrease. In addition, the tensile and creep properties of the as-cast alloys vary with Y content. Namely, with Y content increasing from 0.86% to 2.68%, the creep properties gradually increase, whereas the tensile properties firstly increase and attain the maximum at 1.77% Y, beyond that they decrease. Amongst the as-cast alloys with 0.86% Y, 1.19% Y, 1.77% Y and 2.68% Y, the alloy with 1.77% Y exhibits the relatively optimal tensile and creep properties.展开更多
The effect of zinc addition on the microstructure and mechanical properties of Mg-7Y-3Sm-0.5Zr casting alloy was investigated. Creep test was carried out at 200-300 °C under 50-120 MPa. Within the limits of the c...The effect of zinc addition on the microstructure and mechanical properties of Mg-7Y-3Sm-0.5Zr casting alloy was investigated. Creep test was carried out at 200-300 °C under 50-120 MPa. Within the limits of the creep test conditions used in this study, the creep activation energy of the investigated alloys was in the range of 156-221 kJ/mol. The microstructure evolution during creep was characterized by optical metallography, SEM and TEM. The results show that the creep life of the alloy is increased from 52.2 to 152.8 h at 300 °C under 50 MPa by only 1% addition of Zn, though both the alloys have similar creep behaviors below 250 °C, which suggests that the thermally stable compound and lamellar structure can improve the high temperature creep resistance of the alloy with the addition of Zn.展开更多
In order to obtain a high-performance surface on TiAl alloy that can meet the requirements in hot corrosion environment,Si-Al-Y coatings were fabricated by pack cementation process at 1050℃for 4 h.Corrosion behaviors...In order to obtain a high-performance surface on TiAl alloy that can meet the requirements in hot corrosion environment,Si-Al-Y coatings were fabricated by pack cementation process at 1050℃for 4 h.Corrosion behaviors of the TiAl alloy with and without Si-Al-Y coatings are compared to illustrate the factors and corresponding mechanism in molten salt environment of 25 wt%K2SO4 and 75 wt%Na2SO4 at 900°C.The obtained Si-Al-Y coating was mainly composed of a TiSi2 outer layer,a(Ti,X)5Si4 and(Ti,X)5Si3(X represents Nb or Cr element)middle layer,a TiAl2 inner layer and a Al-rich inter-diffusion zone.The inter-phase selective corrosion containing corrosion pits extending alongα2 phase from lamellar interfaces in hot corrosion tested TiAl alloy was observed.However,by being coated with Si-Al-Y coating,the hot corrosion performance of TiAl alloy was improved remarkably.展开更多
Magnesium alloys possess lots of unique advantages as one of the most promising materials. However, relatively poor mechanical properties limit the application of Mg alloys. As a relatively excellent strengthing phase...Magnesium alloys possess lots of unique advantages as one of the most promising materials. However, relatively poor mechanical properties limit the application of Mg alloys. As a relatively excellent strengthing phase, icosahedral quasicrystal phased-phase) has great influence on Mg-Zn-Y-(Zr) alloys. The yield strength of Mg-Zn-Y-(Zr) alloys could reach 150 - 450 MPa at room temperature with different I-phase volume fractions, therefore the formation of I-phase has been regared as an effective method to improve the performance of Mg alloys. In this review paper, a series of researches about the Mg-Zn-Y-(Zr) alloys containing I-phase have been discussed, mainly including the current understandings about formation mechanism and I- phase structure, its orientation relationship with a-Mg matrix, and the effect of I-phase on Mg-Zn-Y-(Zr) alloys.展开更多
To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was in...To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.展开更多
In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and ...In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.展开更多
基金Project(2007CB613700)supported by the National Basic Research Program of ChinaProject(2011BAE22B01-3)supported by the National Key Technologies R&D Program of China+1 种基金Project(2010DFR50010,2008DFR50040)supported by the International Scientific and Technological Cooperation Program of Ministry of Science and Technology of ChinaProject(CSTC,2010AA4048)supported by Chongqing Science and Technology Commission,China
文摘The effects of Y on the microstructure and mechanical properties of Mg-6Zn-lMn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mechanical properties of Mg-6Zn-lMn alloy. Varied phases compositions, including Mg7Zn3, I-phase (Mg3YZn6), W-phase (Mg3Y2Zn3) and X-phase (MgI2YZn), are obtained by adjusting the Zn to Y mass ratio. Mn element exists as the fine Mn particles, which are well distributed in the alloy. Thermal analysis and microstructure observation reveal that the phase stability follows the trend of X〉W〉/〉MgTZn3. In addition, Y can improve the mechanical properties of Mg-Zn-Mn alloy significantly, and the alloy with Y content of 6.09% has the best mechanical properties. The high strength is mainly due to the strengthening by the grain size refinement, dispersion strengthening by fine Mn particles, and introduction of the Mg-Zn-Y ternary phases.
基金Project(50725413)supported by the National Natural Science Foundation of China
文摘The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explained from the ternary phase diagram calculation. The results show that the formation of the secondary phases in Mg-Zn-Y-Zr alloys firmly depends on the mole ratio of Y to Zn, and X (Mg 12 YZn)-phase, W (Mg 3 Y 2 Zn 3 )-phase and I (Mg 3 YZn 6 )-phase come out in sequence as the ratio of Y to Zn decreases. The mole ratios of Y to Zn with the corresponding phase constituent are suggested quantitatively as follows: the phase constituent is α-Mg + I when the mole ratio of Y to Zn is about 0.164; α-Mg + I +W when the mole ratio of Y to Zn is in the range of 0.164 0.33;α-Mg +W when the mole ratio of Y to Zn is about 0.33; α-Mg +W+X when the mole ratio of Y to Zn is in the range of 0.33 1.32; and α-Mg +X when the mole ratio of Y to Zn is about 1.32. The results also offer a guideline for alloy selection and alloy design in Mg-Zn-Y-Zr system.
基金Project (50875031) supported by the National Natural Science Foundation of ChinaProject (DUT122D205) supported by the Fundamental Research Funds for the Central Universities,China
文摘Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were correspondingly investigated. The results indicate that the Mg element is homogeneously distributed in the matrix and the fragmentized Cu2Te phase is dispersed in the matrix after hot rolling. Then, the Cu2Te phase is further stretched to strip shape after the cold rolling process. The microstructures of the cold-rolled alloy keep unchanged for the sample annealed below 390 ℃ for 1 h. However, after annealing at 550 ℃ for 1 h, the copper alloy with fibrous microstructures formed during the cold rolling process recrystallizes, leading to an obvious drop of hardening effect and an increase of electrical conductivity. The Cu-Mg-Te-Y alloy with better comprehensive properties is obtained by annealing at 360-390 ℃.
基金Project(2013CB632200)supported by National Basic Research Program of ChinaProject(2010DFR50010)supported by International Scientific and Technological Cooperation Program of Ministry of Science and Technology of ChinaProject supported by Sharing Fund of Chongqing University’s Large-scale Equipment,China
文摘The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn and Mg-6Zn-1Mn-4Sn-0.5Y alloys under extrusion and T6 aging conditions were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM) and tensile test. The results show that Y element refines the grains and improves the comprehensive mechanical properties of ZMT614-0.5Y both in as-extruded and T6 states. The phase compositions of Mg-6Zn-1Mn-4Sn-0.5Y are α-Mg, Mg Zn2, Mn, Mg2 Sn and Mg Sn Y phases. After T6 treatment, the ultimate tensile strength(UTS) and yield strength(YS) increase while the elongation decreases severely. For both of these alloys, the theoretical results combined with the experimental values demonstrate that the grain boundary strengthening and solid solution strengthening play an important role in enhancing the YS in the as-extruded state, while the precipitation strengthening is the key factor for the enhancement of YS in the T6 state.
基金Project(2014JZ012)supported by the Natural Science Program for Basic Research in Key Areas of Shaanxi Province,China
文摘In order to improve the high temperature oxidation resistance of TiAl alloy, Y modified silicide coatings were prepared by pack cementation process at 1030, 1080 and 1130 °C, respectively, for 5 h. The microstructures, phase constitutions and oxidation behavior of these coatings were studied. The results show that the coating prepared by co-depositing Si?Y at 1080 °C for 5 h has a multiple layer structure: a superficial zone consisting of Al-rich (Ti,Nb)5Si4 and (Ti,Nb)5Si3, an out layer consisting of (Ti,Nb)Si2, a middle layer consisting of (Ti,Nb)5Si4 and (Ti,Nb)5Si3, and aγ-TiAl inner layer. Co-deposition temperature imposes strong influences on the coating structure. The coating prepared by Si?Y co-depositing at 1080 °C for 5 h shows relatively good oxidation resistance at 1000 °C in air, and the oxidation rate constant of the coating is about two orders of magnitude lower than that of the bare TiAl alloy.
基金Project(2007CB613704)supported by the National Basic Research Program of China
文摘A high strength GW94 alloy with fully recrystallized microstructure and equiaxed ultrafine grains of submicron size was produced by multiaxial forging and ageing. The alloy exhibits an ultimate tensile strength of 377 MPa, proof stress of 295 MPa and elongation to failure of 21.7%. The ductility is improved in comparison with that of the conventional extrusion processing. Superplastic ductility is achieved in tensile testing at 573 K with a maximum elongation of 450%. These high ductility and high strength are attributed to the coexistence of fully recrystallized grains and nanoscale Mg 5 (Gd, Y) particles dynamically precipitated at grain boundaries.
基金Foundation item:Project(2007CB613704)supported by the National Basic Research Program of ChinaProject(CSTC2013jcyj C60001)supported by the Chongqing Science and Technology Commission of ChinaProject(CQUT1205)supported by the Open Funds from Key Laboratory of Manufacture and Test Techniques for Automobile Parts(Chongqing University of Technology),Ministry of Education,China
文摘The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly composed ofα-Mg, Mg2Ca, Ca2Mg6Zn3,I (Mg3YZn6) andW (Mg3Y2Zn3) phases. However, with Y content increasing from 0.86% to 2.68%, the amount of the Ca2Mg6Zn3 phase gradually decreases but that of theI (Mg3YZn6) andW (Mg3Y2Zn3) phases gradually increases. Furthermore, an increase in Y content from 0.86% to 2.68% also causes the grain size of the as-cast alloys to gradually decrease. In addition, the tensile and creep properties of the as-cast alloys vary with Y content. Namely, with Y content increasing from 0.86% to 2.68%, the creep properties gradually increase, whereas the tensile properties firstly increase and attain the maximum at 1.77% Y, beyond that they decrease. Amongst the as-cast alloys with 0.86% Y, 1.19% Y, 1.77% Y and 2.68% Y, the alloy with 1.77% Y exhibits the relatively optimal tensile and creep properties.
基金Project (51074106) supported by the National Natural Science Foundation of ChinaProject (2009AA033501) supported by the National High-Tech Research and Development Program of China+1 种基金Projects (2011BAE22B01-5, 2006BAE04B01-2) supported by the National Science and Technology Pillar Program during the 12th Five-Year Plan PeriodProject (06SR07104) supported by the International Cooperation Fund of Shanghai Science and Technology Committee, Shanghai/Rhone-Alpes Science and Technology Cooperation Fund,China
文摘The effect of zinc addition on the microstructure and mechanical properties of Mg-7Y-3Sm-0.5Zr casting alloy was investigated. Creep test was carried out at 200-300 °C under 50-120 MPa. Within the limits of the creep test conditions used in this study, the creep activation energy of the investigated alloys was in the range of 156-221 kJ/mol. The microstructure evolution during creep was characterized by optical metallography, SEM and TEM. The results show that the creep life of the alloy is increased from 52.2 to 152.8 h at 300 °C under 50 MPa by only 1% addition of Zn, though both the alloys have similar creep behaviors below 250 °C, which suggests that the thermally stable compound and lamellar structure can improve the high temperature creep resistance of the alloy with the addition of Zn.
基金Project(2020AAC02025)supported by the Natural Science Foundation of Ningxia Province,ChinaProject(51961003)supported by the National Natural Science Foundation of China+1 种基金Project(TJGC2019040)supported by the Ningxia Youth Talents Supporting Program,ChinaProject(2020xyzc103)supported by the Foundation of North Minzu University,China。
文摘In order to obtain a high-performance surface on TiAl alloy that can meet the requirements in hot corrosion environment,Si-Al-Y coatings were fabricated by pack cementation process at 1050℃for 4 h.Corrosion behaviors of the TiAl alloy with and without Si-Al-Y coatings are compared to illustrate the factors and corresponding mechanism in molten salt environment of 25 wt%K2SO4 and 75 wt%Na2SO4 at 900°C.The obtained Si-Al-Y coating was mainly composed of a TiSi2 outer layer,a(Ti,X)5Si4 and(Ti,X)5Si3(X represents Nb or Cr element)middle layer,a TiAl2 inner layer and a Al-rich inter-diffusion zone.The inter-phase selective corrosion containing corrosion pits extending alongα2 phase from lamellar interfaces in hot corrosion tested TiAl alloy was observed.However,by being coated with Si-Al-Y coating,the hot corrosion performance of TiAl alloy was improved remarkably.
基金National Natural Science Foundation of China(Nos.U1610123,51674226,51574207)International Cooperation project of the Ministry of Science and Technology of China(No.2014DFA50320)Science and Technology Major Project of Shanxi Province(No.MC2016-06)
文摘Magnesium alloys possess lots of unique advantages as one of the most promising materials. However, relatively poor mechanical properties limit the application of Mg alloys. As a relatively excellent strengthing phase, icosahedral quasicrystal phased-phase) has great influence on Mg-Zn-Y-(Zr) alloys. The yield strength of Mg-Zn-Y-(Zr) alloys could reach 150 - 450 MPa at room temperature with different I-phase volume fractions, therefore the formation of I-phase has been regared as an effective method to improve the performance of Mg alloys. In this review paper, a series of researches about the Mg-Zn-Y-(Zr) alloys containing I-phase have been discussed, mainly including the current understandings about formation mechanism and I- phase structure, its orientation relationship with a-Mg matrix, and the effect of I-phase on Mg-Zn-Y-(Zr) alloys.
基金The work was supported by the National Natural Science Foundation of China(No.51401115)the Promoted Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,China(No.BS2013CL034)partially by the Fundamental Research Funds of Shandong University,China(2016JC016).
文摘To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.
基金Project(51961003)supported by the National Natural Science Foundation of ChinaProject(NGY2018-148)supported by the Science and Technology Research of Ningxia Colleges,ChinaProject(NZ16083)supported by Key Program of Natural Science Foundation of Ningxia,China
文摘In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.