Ti is regarded as one of the promising grain refiners in cast Al-Li-Cu alloys,but few research works have been done on its independent role.In this study,the effect of Ti on the microstructure evolution and mechanical...Ti is regarded as one of the promising grain refiners in cast Al-Li-Cu alloys,but few research works have been done on its independent role.In this study,the effect of Ti on the microstructure evolution and mechanical properties of cast Al-2Li-2Cu-0.5Mg base alloy was investigated.The results revealed that the grains can be prominently refined with the increase of Ti addition.After adding Ti,high density TiB_(2)-Al_(3)Ti composite particles with a low lattice misfit form as heterogeneous nucleation sites for the α-Al matrix.δ’(Al3Li) and T_(1)(Al_(2)CuLi) precipitates that provide enhanced strength are dominated in the alloys after T6 aging treatment.The average size of both δ’ and half-width of δ’-precipitation free zone(PFZ) decreases gradually with the increase of Ti content.This is because the higher binding energy between Ti atoms and vacancies limits the diffusion efficiency of Li atoms,and thus results in a higher ductility.Additionally,no nano-sized Al_(3)Ti or core-shell structure of Al_(3)(Li,Ti) particles are found.The tensile property test results indicate that the Al-2Li-2Cu-0.5Mg alloy achieves optimal properties after aging at 175 °C for 32 h when 0.15wt.% Ti is added.It exhibits a yield strength of 352±5 MPa,an ultimate tensile strength of 423±6 MPa,and an elongation of(3±0.4)%.These findings are expected to offer a reliable theoretical guidance for the industrial composition design of the Al-Li-Cu series cast alloys.展开更多
In this work, the effects of reclaimed sand additions on the microstructure characteristics, mechanical properties and fracture behavior of furan no-bake resin sand have been investigated systematically within the tem...In this work, the effects of reclaimed sand additions on the microstructure characteristics, mechanical properties and fracture behavior of furan no-bake resin sand have been investigated systematically within the temperature range from 25 to 600 oC. The addition of 20%-100% reclaimed sand showed dramatic strength deterioration effect at the same temperature, which is associated with the formation of bonding bridges. Both the ultimate tensile strength(UTS) and compressive strength(CS) of the moulding sand initially increase with the increase of temperature, and then sharply decrease with the further increase of temperature, which is attributed to the thermal decomposition of furan resin. The addition amount of reclaimed sand has a remarkable effect on the room temperature fracture mode, i.e., with the addition of 0-20% reclaimed sand, the fracture mode was mainly cohesive fracture; the fracture mode converts to be mixture fracture mode as the addition of reclaimed sand increases to 35%-70%; further increasing the addition to 100% results in the fracture mode of typical adhesive fracture. The fracture surface of the bonding bridge changes from a semblance of cotton or holes to smooth with the increase of test temperature.展开更多
In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt th...In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification,and the samples of semi-solid slurry were taken by the rapid quenching method.The results show that fine and sphericalα-Mg particles can be obtained under rotating gas bubble stirring treatment.The process parameters such as gas flow rate,cooling rate and rotation speed have significant influence on the morphology of primary solid particles.After rotating gas bubble stirring treatment,the higher the particle density,the finer and rounder the primaryα-Mg particles.The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.展开更多
The rheo-squeeze casting(RSC)process is a newly-developed casting process for high-performance components.In order to further improve the mechanical properties of magnesium alloys,AZ91-2wt.%Ca(AZX912)alloy was prepare...The rheo-squeeze casting(RSC)process is a newly-developed casting process for high-performance components.In order to further improve the mechanical properties of magnesium alloys,AZ91-2wt.%Ca(AZX912)alloy was prepared by the RSC process and then subjected to heat treatment.The microstructure evolution and mechanical properties of AZX912 alloy during heat treatment were investigated.It was found that during solid solution treatment at 410°C,β-Mg_(17)Al_(12) phase with low melting point dissolves intoα-Mg matrix,while the connected network-like Al_2Ca phase with high melting point tends to separate gradually,and the tips of Al_2Ca phase is partially spheroidized.With the increase of solid solution time,the yield strength(YS)of AZX912 alloy decreases gradually while the ultimate tensile strength(UTS)and elongation to failure(E_f)increase continuously.Isothermal ageing at 225°C promotes the precipitation ofβ-Mg_(17)Al_(12) phase in the matrix of AZX912 alloy.The hardness reaches the peak after ageing for 96 h and the increase in hardness is about 24.8%.The precipitation ofβ-Mg_(17)Al_(12) phase during ageing treatment is beneficial to YS but harmful to E_f.The mechanism of microstructure evolution during heat treatment and its effect on mechanical properties are discussed.展开更多
The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr(wt.%) alloys in as-cast, solution treated(T4) and aged(T6) conditions were studied by means of immersion test and electrochemical measurements in 5wt....The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr(wt.%) alloys in as-cast, solution treated(T4) and aged(T6) conditions were studied by means of immersion test and electrochemical measurements in 5wt.% NaCl solution saturated with Mg(OH)_2. It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4; while the corrosion resistance of the permanent mold casting is superior to the sand casting. The morphologies of the corrosion products are similar porous structures consisting of tiny erect flakes perpendicular to the corroded surface of the alloy, irrespective of the heat treatment conditions. Especially, the corrosion film in T4 condition is more compact than that in the other two conditions. In addition, the severer corrosion happening to the as-cast condition is correlated with the galvanic corrosion between the matrix and the eutectic compounds; while improved corrosion resistance for the T4 and T6 conditions is ascribed to the dissolution of the secondary eutectic compounds. The measured corrosion current densities of Mg-10Gd-3Y-0.5Zr alloys in as-cast, T4, and T6 conditions are 36 μA?cm^(-2), 10 μA?cm^(-2), and 33 μA?cm^(-2), respectively. The proposed equivalent circuit [Rs(CPE_1(R_t(R_fCPE_2))] by Zview software matches well with the tested electrochemical impedance spectra(EIS) data.展开更多
Magnesium-lithium(Mg-Li) alloy,as the lightest metal structure material,has unparalleled market prospects in aerospace,weapons and equipment,electronic technology,transportation,and many other fields.However,it is har...Magnesium-lithium(Mg-Li) alloy,as the lightest metal structure material,has unparalleled market prospects in aerospace,weapons and equipment,electronic technology,transportation,and many other fields.However,it is hard to balance the superlight and high strength of Mg-Li alloy,and the inferior high-temperature strength and poor high-temperature stability limit the wide application of Mg-Li alloy.At present,the main methods to improve the mechanical properties of Mg-Li alloy are alloying,grain refinement,and compound strengthening.The domestic and overseas research progress in the strengthening and toughening methods and mechanisms of Mg-Li alloy are reviewed,and the future development of the high strength and high toughness Mg-Li alloy is prospected.展开更多
基金National Natural Science Foundation of China(Nos.U2037601,51821001)Key Basic Research Project of the National Basic Strengthening Plan,China(No.2022-xxxx-ZD-093-xx)。
基金supported by the Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment (No. SKL202005)the Major Scientific and Technological Innovation Project of Luoyang,China(No. 2201029A)+1 种基金the National Natural Science Foundation of China (Nos. 51771115, 51775334)the Research Program of SAST-SJTU Joint Research Center of Advanced Spaceflight Technologies,China (No. USCAST2020-14)。
基金financially supported by the National Natural Science Foundation of China (Nos.51821001 and 51871148)。
文摘Ti is regarded as one of the promising grain refiners in cast Al-Li-Cu alloys,but few research works have been done on its independent role.In this study,the effect of Ti on the microstructure evolution and mechanical properties of cast Al-2Li-2Cu-0.5Mg base alloy was investigated.The results revealed that the grains can be prominently refined with the increase of Ti addition.After adding Ti,high density TiB_(2)-Al_(3)Ti composite particles with a low lattice misfit form as heterogeneous nucleation sites for the α-Al matrix.δ’(Al3Li) and T_(1)(Al_(2)CuLi) precipitates that provide enhanced strength are dominated in the alloys after T6 aging treatment.The average size of both δ’ and half-width of δ’-precipitation free zone(PFZ) decreases gradually with the increase of Ti content.This is because the higher binding energy between Ti atoms and vacancies limits the diffusion efficiency of Li atoms,and thus results in a higher ductility.Additionally,no nano-sized Al_(3)Ti or core-shell structure of Al_(3)(Li,Ti) particles are found.The tensile property test results indicate that the Al-2Li-2Cu-0.5Mg alloy achieves optimal properties after aging at 175 °C for 32 h when 0.15wt.% Ti is added.It exhibits a yield strength of 352±5 MPa,an ultimate tensile strength of 423±6 MPa,and an elongation of(3±0.4)%.These findings are expected to offer a reliable theoretical guidance for the industrial composition design of the Al-Li-Cu series cast alloys.
基金Project(2016YFB0301004)supported by the National Key Research and Development Program of ChinaProject(51771115)supported by the National Natural Science Foundation of China+3 种基金Project(6141B06310106)supported by the Joint Fund for Space Science and Technology,ChinaProject(009-031-001)supported by the Science and Technology Innovation Program,ChinaProject(USCAST2016-18)supported by the Research Program of Joint Research Center of Advanced Spaceflight Technologies,ChinaProject(SAST2016048)supported by the Science Innovation Foundation of Shanghai Academy of Spaceflight Technology,China
基金financial supports from the National Natural Science Foundation of China (51771115,51775334)Joint Fund for Space Science and Technology (6141B06310106),ChinaChina and National Defense Science and Technology Innovation Special Zone Project (002-002-01),China。
基金Project(2016YFB0301003)supported by the National Key R&D Program of ChinaProject(51871148)supported by the National Natural Science Foundation of ChinaProject(sklmmc-kf18-02)supported by Open Research Fund of the State Key Laboratory of Metal Matrix Composites,China
基金financially supported by the National Natural Science Foundation of China(Nos.51771115,51775334,51821001,U2037601)Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment(No.SKL2020005)。
基金supported by the National Natural Science Foundation of China(Nos.U2037601,51775334 and 51821001)the National Key Research&Development Program of China(No.2016YFB0701205)+2 种基金the Joint Innovation Fund of CALT and College,China(No.CALT2020-TS07)the Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment,China(No.SKL2020005)the Research Program of Joint Research Center of Advanced Spaceflight Technologies,China(No.USCAST2020-14).
基金supported by the National Natural Science Foundation of China (51871148,51821001)the United Fund of National Department of Education and Equipment Development (6141A02033245)the National Key R&D Program of China (2016YFB0301003)。
基金the National Natural Science Foundation of China(Nos.51871148,51821001)the United Fund of National Department of Education and Equipment Development,China(No.6141A02033245).
基金financial supports from National Natural Science Foundation of China(Nos.51775334,51771115,U2037601)Research Program of Joint Research Center of Advanced Spaceflight Technologies,China(No.USCAST2020-14)。
基金sponsored by the National Natural Science Foundation of China(Nos.51275295 and 51201102)the Shanghai Rising–Star Program(No.14QB1403200)Research Fund for the Doctoral Program of Higher Education of China(Nos.20120073120011 and 20130073110052)
文摘In this work, the effects of reclaimed sand additions on the microstructure characteristics, mechanical properties and fracture behavior of furan no-bake resin sand have been investigated systematically within the temperature range from 25 to 600 oC. The addition of 20%-100% reclaimed sand showed dramatic strength deterioration effect at the same temperature, which is associated with the formation of bonding bridges. Both the ultimate tensile strength(UTS) and compressive strength(CS) of the moulding sand initially increase with the increase of temperature, and then sharply decrease with the further increase of temperature, which is attributed to the thermal decomposition of furan resin. The addition amount of reclaimed sand has a remarkable effect on the room temperature fracture mode, i.e., with the addition of 0-20% reclaimed sand, the fracture mode was mainly cohesive fracture; the fracture mode converts to be mixture fracture mode as the addition of reclaimed sand increases to 35%-70%; further increasing the addition to 100% results in the fracture mode of typical adhesive fracture. The fracture surface of the bonding bridge changes from a semblance of cotton or holes to smooth with the increase of test temperature.
基金This project is sponsored by National Natural Science Foundation of China(No.51275295)Funded Projects of SAST-SJTU Joint Research Centre of Advanced Aerospace Technology(No.USCAST2012-15)Research Fund for the Doctoral Program of Higher Education of China(No.20120073120011).
文摘In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification,and the samples of semi-solid slurry were taken by the rapid quenching method.The results show that fine and sphericalα-Mg particles can be obtained under rotating gas bubble stirring treatment.The process parameters such as gas flow rate,cooling rate and rotation speed have significant influence on the morphology of primary solid particles.After rotating gas bubble stirring treatment,the higher the particle density,the finer and rounder the primaryα-Mg particles.The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.
基金financially supported by National Natural Science Foundation of China(No.51601076 and No.51401093)Natural Science Fund for Colleges and Universities in Jiangsu Province(No.16KJB430013)
文摘The rheo-squeeze casting(RSC)process is a newly-developed casting process for high-performance components.In order to further improve the mechanical properties of magnesium alloys,AZ91-2wt.%Ca(AZX912)alloy was prepared by the RSC process and then subjected to heat treatment.The microstructure evolution and mechanical properties of AZX912 alloy during heat treatment were investigated.It was found that during solid solution treatment at 410°C,β-Mg_(17)Al_(12) phase with low melting point dissolves intoα-Mg matrix,while the connected network-like Al_2Ca phase with high melting point tends to separate gradually,and the tips of Al_2Ca phase is partially spheroidized.With the increase of solid solution time,the yield strength(YS)of AZX912 alloy decreases gradually while the ultimate tensile strength(UTS)and elongation to failure(E_f)increase continuously.Isothermal ageing at 225°C promotes the precipitation ofβ-Mg_(17)Al_(12) phase in the matrix of AZX912 alloy.The hardness reaches the peak after ageing for 96 h and the increase in hardness is about 24.8%.The precipitation ofβ-Mg_(17)Al_(12) phase during ageing treatment is beneficial to YS but harmful to E_f.The mechanism of microstructure evolution during heat treatment and its effect on mechanical properties are discussed.
基金sponsored by the National Natural Science Foundation of China(No.51275295)Research Fund for the Doctoral Program of Higher Education of China(Nos.20120073120011 and 20130073110052)
文摘The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr(wt.%) alloys in as-cast, solution treated(T4) and aged(T6) conditions were studied by means of immersion test and electrochemical measurements in 5wt.% NaCl solution saturated with Mg(OH)_2. It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4; while the corrosion resistance of the permanent mold casting is superior to the sand casting. The morphologies of the corrosion products are similar porous structures consisting of tiny erect flakes perpendicular to the corroded surface of the alloy, irrespective of the heat treatment conditions. Especially, the corrosion film in T4 condition is more compact than that in the other two conditions. In addition, the severer corrosion happening to the as-cast condition is correlated with the galvanic corrosion between the matrix and the eutectic compounds; while improved corrosion resistance for the T4 and T6 conditions is ascribed to the dissolution of the secondary eutectic compounds. The measured corrosion current densities of Mg-10Gd-3Y-0.5Zr alloys in as-cast, T4, and T6 conditions are 36 μA?cm^(-2), 10 μA?cm^(-2), and 33 μA?cm^(-2), respectively. The proposed equivalent circuit [Rs(CPE_1(R_t(R_fCPE_2))] by Zview software matches well with the tested electrochemical impedance spectra(EIS) data.
基金the National Natural Science Foundation of China(Nos.51771115,51775334,51821001 and U2037601)the Joint Fund for Space Science and Technology(No.6141B06310106)。
文摘Magnesium-lithium(Mg-Li) alloy,as the lightest metal structure material,has unparalleled market prospects in aerospace,weapons and equipment,electronic technology,transportation,and many other fields.However,it is hard to balance the superlight and high strength of Mg-Li alloy,and the inferior high-temperature strength and poor high-temperature stability limit the wide application of Mg-Li alloy.At present,the main methods to improve the mechanical properties of Mg-Li alloy are alloying,grain refinement,and compound strengthening.The domestic and overseas research progress in the strengthening and toughening methods and mechanisms of Mg-Li alloy are reviewed,and the future development of the high strength and high toughness Mg-Li alloy is prospected.
