The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring...The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.展开更多
The effects of high pressure rheo-squeeze casting(HPRC) on the Fe-rich phases(FRPs) and mechanical properties of Al-17 Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration(...The effects of high pressure rheo-squeeze casting(HPRC) on the Fe-rich phases(FRPs) and mechanical properties of Al-17 Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration(UV) and then formed by high-pressure squeeze casting(HPSC). The FRPs in the as-cast HPSC Al-17 Si-1 Fe alloys only contained a long, needle-shaped β-Al5 Fe Si phase at 0 MPa. In addition to the β-Al5 Fe Si phase, the HPSC Al-17 Si-1.5 Fe alloy also contained the plate-shaped δ-Al4 Fe Si2 phase. A fine, block-shaped δ-Al4 Fe Si2 phase was formed in the Al-17 Si-1 Fe alloy treated by UV. The size of FRPs decreased with increasing pressure. After UV treatment, solidification under pressure led to further refinement of the FRPs. Considering alloy samples of the same composition, the ultimate tensile strength(UTS) of the HPRC samples was higher than that of the HPSC samples, and the UTS increased with increasing pressure. The UTS of the Al-17 Si-1 Fe alloy formed by HPSC exceeded that of the Al-17 Si-1.5 Fe alloy formed in the same manner under the same pressure. Conversely, the UTS of the Al-17 Si-1 Fe alloy formed by HPRC decreased to a value lower than that of the Al-17 Si-1.5 Fe alloy formed in the same manner.展开更多
The microstructure,mechanical properties and flame resistance behavior of the AZ91−1Ce alloys with different Ca additions were firstly investigated.Then,the effect of processing parameters,including applied pressures ...The microstructure,mechanical properties and flame resistance behavior of the AZ91−1Ce alloys with different Ca additions were firstly investigated.Then,the effect of processing parameters,including applied pressures and rotation speeds,on the microstructure and mechanical properties of the rheo-squeeze casting AZ91−1Ce−2Ca alloy was studied.The results indicate that with the increase of Ca content,the microstructure is refined and the flame resistance of the AZ91−1Ce−xCa alloys increases.But when the Ca content exceeds 1 wt.%,with the Ca content increasing,the mechanical properties of the AZ91−1Ce−xCa alloys reduce rapidly.For rheo-squeeze casting process,the increase of applied pressure and rotation speed can both bring about significant refinement in the microstructure of the AZ91−1Ce−2Ca alloy and reduction of the porosity,so the mechanical properties increase.Compared to conventional casting,the AZ91−1Ce alloy with the addition of 2 wt.%Ca by rheo-squeeze casting not only guarantees the oxidation resistance(801℃),but also improves mechanical properties.展开更多
In this study,a high-ductility AZ91 magnesium alloy was fabricated by the novel continuous rheo-squeeze casting-extrusion(CRSCE)process.The semi-solid slurry was prepared by ultrasonic vibration(UV)treatment,then soli...In this study,a high-ductility AZ91 magnesium alloy was fabricated by the novel continuous rheo-squeeze casting-extrusion(CRSCE)process.The semi-solid slurry was prepared by ultrasonic vibration(UV)treatment,then solidified under pressure,and finally hot extruded.UV treatment can reduce the Al element content in primary grains and increase it in secondary grains.The refined Mg_(17)Al_(12) phase was scattered along secondary grain boundaries and then stretched into narrow,fibrous bands during the hot extrusion.The fibrous bands with proper separation distances can accelerate the dynamic recrystallization(DRX)process and suppress the growth of DRXed grains.Microcracks were initiated inside the brittle Mg_(17)Al_(12) phase and tended to propagate along the continuously distributed Mg_(17)Al_(12) phase during the tensile test.Thus,the tiny Mg_(17)Al_(12) phase in the billet and narrow,fibrous bands in as-extruded rods can prevent cracks from spreading and enhance ductility.Therefore,excellent comprehensive mechanical properties were obtained,with an ultimate tensile strength of 326.3 MPa and an elongation of 16.46%.The CRSCE method offers a novel way to fabricate high-ductility and high-alloyed magnesium alloys without homogenization.Microstructure regulation mechanisms of CRSCE,microstructural hereditary laws,and the effect of the Mg_(17)Al_(12) phase on mechanical properties were further discussed.展开更多
Although icosahedral quasicrystal phase(denoted as I-phase)has been verified as an outstanding reinforcing phase,the mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloys fabricated by traditional casting pr...Although icosahedral quasicrystal phase(denoted as I-phase)has been verified as an outstanding reinforcing phase,the mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloys fabricated by traditional casting processes are still unsatisfactory due to the serious segregation of intermetallic compounds.In this study,the microstructure and mechanical properties of Mg-12Zn-2Y alloy fabricated by different casting processes,including permanent mold casting,squeeze casting and rheo-squeeze casting with ultrasonic vibration,were systematically investigated and compared.The results show that massive,large-sized I-phase and Mg7Zn3 phase gather together in the permanent mold cast sample,while the squeeze casting process leads to the transformation of I-phase into fine lamellar morphology and the amount of Mg7Zn3 decreases.As to the rheo-squeeze casting process,when the ultrasonic vibration is exerted with power from 800 W to 1,600 W,theα-Mg grains are refined and spheroidized to a large extent,and the lamellar spacing of the eutectic structure is significantly reduced,accompanied by some tiny granular I-phase scattering in theα-Mg matrix.However,when the ultrasonic power continuously increases to 2,400 W,the eutectic structure becomes coarse.The best mechanical properties of the rheo-squeeze cast alloy are obtained when the ultrasonic power is 1,600 W.The microhardness,yield strength,ultimate tensile strength and elongation are 79.9 HV,140 MPa,236 MPa,and 3.25%,which are 44.1%,26.1%,25.5%,132.1%respectively higher than the corresponding values of the squeeze casting sample,and are 47.6%,44.3%,69.8%,and 253.3%respectively higher than the corresponding values of the permanent mold casting sample.展开更多
基金Project(2006AA03Z115) supported by the National Hi-tech Research and Development Program of ChinaProject(2006CB605203) supported by the National Basic Research Program of ChinaProject(50774007) supported by the National Natural Science Foundation of China
文摘The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.
基金financially supported by the National Natural Science Foundation of China (No. 51605342)the China Postdoctoral Science Foundation (No. 2015M572135)the Open Research Fund Program of Hubei Provincial Key Laboratory of Chemical Equipment Intensification and Intrinsic Safety (No. 2016KA01)
文摘The effects of high pressure rheo-squeeze casting(HPRC) on the Fe-rich phases(FRPs) and mechanical properties of Al-17 Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration(UV) and then formed by high-pressure squeeze casting(HPSC). The FRPs in the as-cast HPSC Al-17 Si-1 Fe alloys only contained a long, needle-shaped β-Al5 Fe Si phase at 0 MPa. In addition to the β-Al5 Fe Si phase, the HPSC Al-17 Si-1.5 Fe alloy also contained the plate-shaped δ-Al4 Fe Si2 phase. A fine, block-shaped δ-Al4 Fe Si2 phase was formed in the Al-17 Si-1 Fe alloy treated by UV. The size of FRPs decreased with increasing pressure. After UV treatment, solidification under pressure led to further refinement of the FRPs. Considering alloy samples of the same composition, the ultimate tensile strength(UTS) of the HPRC samples was higher than that of the HPSC samples, and the UTS increased with increasing pressure. The UTS of the Al-17 Si-1 Fe alloy formed by HPSC exceeded that of the Al-17 Si-1.5 Fe alloy formed in the same manner under the same pressure. Conversely, the UTS of the Al-17 Si-1 Fe alloy formed by HPRC decreased to a value lower than that of the Al-17 Si-1.5 Fe alloy formed in the same manner.
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)。
文摘The microstructure,mechanical properties and flame resistance behavior of the AZ91−1Ce alloys with different Ca additions were firstly investigated.Then,the effect of processing parameters,including applied pressures and rotation speeds,on the microstructure and mechanical properties of the rheo-squeeze casting AZ91−1Ce−2Ca alloy was studied.The results indicate that with the increase of Ca content,the microstructure is refined and the flame resistance of the AZ91−1Ce−xCa alloys increases.But when the Ca content exceeds 1 wt.%,with the Ca content increasing,the mechanical properties of the AZ91−1Ce−xCa alloys reduce rapidly.For rheo-squeeze casting process,the increase of applied pressure and rotation speed can both bring about significant refinement in the microstructure of the AZ91−1Ce−2Ca alloy and reduction of the porosity,so the mechanical properties increase.Compared to conventional casting,the AZ91−1Ce alloy with the addition of 2 wt.%Ca by rheo-squeeze casting not only guarantees the oxidation resistance(801℃),but also improves mechanical properties.
基金funded by the National Natural Science Foundation of China(No.52175321).
文摘In this study,a high-ductility AZ91 magnesium alloy was fabricated by the novel continuous rheo-squeeze casting-extrusion(CRSCE)process.The semi-solid slurry was prepared by ultrasonic vibration(UV)treatment,then solidified under pressure,and finally hot extruded.UV treatment can reduce the Al element content in primary grains and increase it in secondary grains.The refined Mg_(17)Al_(12) phase was scattered along secondary grain boundaries and then stretched into narrow,fibrous bands during the hot extrusion.The fibrous bands with proper separation distances can accelerate the dynamic recrystallization(DRX)process and suppress the growth of DRXed grains.Microcracks were initiated inside the brittle Mg_(17)Al_(12) phase and tended to propagate along the continuously distributed Mg_(17)Al_(12) phase during the tensile test.Thus,the tiny Mg_(17)Al_(12) phase in the billet and narrow,fibrous bands in as-extruded rods can prevent cracks from spreading and enhance ductility.Therefore,excellent comprehensive mechanical properties were obtained,with an ultimate tensile strength of 326.3 MPa and an elongation of 16.46%.The CRSCE method offers a novel way to fabricate high-ductility and high-alloyed magnesium alloys without homogenization.Microstructure regulation mechanisms of CRSCE,microstructural hereditary laws,and the effect of the Mg_(17)Al_(12) phase on mechanical properties were further discussed.
基金financially supported by the Natural Science Foundation of Anhui Province(No.1908085QE197)the State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(P2019-024)the Fundamental Research Funds for the Central Universities(JZ2019HGTA0043)。
文摘Although icosahedral quasicrystal phase(denoted as I-phase)has been verified as an outstanding reinforcing phase,the mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloys fabricated by traditional casting processes are still unsatisfactory due to the serious segregation of intermetallic compounds.In this study,the microstructure and mechanical properties of Mg-12Zn-2Y alloy fabricated by different casting processes,including permanent mold casting,squeeze casting and rheo-squeeze casting with ultrasonic vibration,were systematically investigated and compared.The results show that massive,large-sized I-phase and Mg7Zn3 phase gather together in the permanent mold cast sample,while the squeeze casting process leads to the transformation of I-phase into fine lamellar morphology and the amount of Mg7Zn3 decreases.As to the rheo-squeeze casting process,when the ultrasonic vibration is exerted with power from 800 W to 1,600 W,theα-Mg grains are refined and spheroidized to a large extent,and the lamellar spacing of the eutectic structure is significantly reduced,accompanied by some tiny granular I-phase scattering in theα-Mg matrix.However,when the ultrasonic power continuously increases to 2,400 W,the eutectic structure becomes coarse.The best mechanical properties of the rheo-squeeze cast alloy are obtained when the ultrasonic power is 1,600 W.The microhardness,yield strength,ultimate tensile strength and elongation are 79.9 HV,140 MPa,236 MPa,and 3.25%,which are 44.1%,26.1%,25.5%,132.1%respectively higher than the corresponding values of the squeeze casting sample,and are 47.6%,44.3%,69.8%,and 253.3%respectively higher than the corresponding values of the permanent mold casting sample.
