The microstructure and corrosion behavior of the as-homogenized and as-extruded Mg-xLi-3Al-2Zn-0.5Y alloys(x=4,8,12,wt.%)were studied.The results show that as the Li content increases from 4%to 12%,the matrix transfer...The microstructure and corrosion behavior of the as-homogenized and as-extruded Mg-xLi-3Al-2Zn-0.5Y alloys(x=4,8,12,wt.%)were studied.The results show that as the Li content increases from 4%to 12%,the matrix transfers from singleα-Mg phase,(α-Mg+β-Li)dual phase to singleβ-Li phase.A mixed corrosion feature of intergranular corrosion and pitting corrosion occurs in the Mg-4Li-3Al-2Zn-0.5Y and Mg-12Li-3Al-2Zn-0.5Y alloys.The former is related to the precipitated AlLi phase along the grain boundaries,and the latter is related to the high potential difference between the second phase and the matrix.The corrosion resistance of the as-extruded alloys is better than that of the as-homogenized alloys.The superior corrosion resistance of the as-extruded Mg-8Li-3Al-2Zn-0.5Y alloy with the lowest corrosion rate(P_(W)=(0.63±0.26)mm/a)is attributed to the more uniform distribution of second phases,the protectiveα-Mg phase via sacrificing theβ-Li phase and the relatively integrated oxide film.展开更多
Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined ...Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.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
Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microst...Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microstructure of RS ribbons.The results show that there is high density of particles distributed within grains and at grain boundaries in the region near wheel side.The particle density is decreased in the middle region and free surface region.The alloy is predominantly composed of supersaturated--Mg solid solution,T phase and W phase;meanwhile,a few icosahedral quasicrystalline and Mg4Zn7 particles are also observed.The T phase is confirmed having a body-centered orthorhombic structure that is transformed from the body-centered tetragonal structure Mg12Ce phase due to the partial substitution of Mg atoms by Zn.展开更多
The electromagnetic direct chill （EMDC） casting process is a welt-established production route for aluminum alloy ingot, however, the skin effect restricts the casting diameter. In order to avoid this problem, annul...The electromagnetic direct chill （EMDC） casting process is a welt-established production route for aluminum alloy ingot, however, the skin effect restricts the casting diameter. In order to avoid this problem, annulus electromagnetic direct chill （A-EMDC） casting process has been developed. A three-dimension finite element computational model of A-EMDC casting process was established by using ANSYS Magnetic-Nodal programs and FLOTRAN CFD programs. Microstruetures of A-EMDC casting semi-solid Al-6Si-3Cu-Mg alloy billets were investigated. Two pairs of vortexes occur within the crystallizer with opposite direction in A-EMDC. The annulus gap is advantageous to increasing circulate flow, reducing the temperature gradient as well as shallowing liquid sump depth. The microstructure obtained by A-EMDC is globular or rosette-like, and the microstructure is homogeneous in the billet.展开更多
The mechanical properties of Al-6Mg alloy with three treatment states （H112, O and cold-extruded states） were investigated at room and high temperatures using an INSTRON machine and a Split Hopkinson Pressure Bar （...The mechanical properties of Al-6Mg alloy with three treatment states （H112, O and cold-extruded states） were investigated at room and high temperatures using an INSTRON machine and a Split Hopkinson Pressure Bar （SHPB）. Stress-strain curves of the alloy with different processes were obtained at a quasi-static strain rate of 5×10-4 s-1and dynamic strain rates of 1 400-4 200 s-1, respectively. The results suggest that, at room temperature, the three processed Al-6Mg alloys are all low sensitive to strain rate. The O state Al-6Mg alloy （Al-6Mg-O） exhibits the most ductility, while the cold-extruded Al-6Mg alloy （Al-6Mg-C） displays the highest strength. At elevated temperatures, the yield stresses and the differences in yield stress of the three processed alloys all decrease with increasing temperature under the quasi-static strain rate of 5×10-4 s-1. Based on test results, modified Johnson-Cook （JC） constitutive models for the three processed Al-6Mg alloys were developed. The microstructures before and after deformation were examined by electron backscattered diffraction （EBSD） and further dynamic recrystallization （DRX） at the strain rate of 3 300 s-1 was discussed.展开更多
A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microsc...A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microscopy(SEM),glancing angle X-ray diffractometry(GAXRD) and various electrochemical methods.The micro-arc oxidation process consists of three stages and corresponds with different coating structures.In the initial stage,the coating thickness is linearly increased and is controlled by electrochemical polarization.In the second stage,the coating grows mainly inward and accords with parabolic regularity.In the third stage,the loose coating forms and is controlled by local arc light.The looser coating is mainly composed of MgSiO3 and the compact coating is mainly composed of MgO.From micro-arc oxidation stage to local arc light stage,the corrosion resistance of the coated alloy firstly increases and then decreases.The satisfied corrosion resistance corresponds to the coating time ranging from 6 to10 min.展开更多
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)。
文摘The microstructure and corrosion behavior of the as-homogenized and as-extruded Mg-xLi-3Al-2Zn-0.5Y alloys(x=4,8,12,wt.%)were studied.The results show that as the Li content increases from 4%to 12%,the matrix transfers from singleα-Mg phase,(α-Mg+β-Li)dual phase to singleβ-Li phase.A mixed corrosion feature of intergranular corrosion and pitting corrosion occurs in the Mg-4Li-3Al-2Zn-0.5Y and Mg-12Li-3Al-2Zn-0.5Y alloys.The former is related to the precipitated AlLi phase along the grain boundaries,and the latter is related to the high potential difference between the second phase and the matrix.The corrosion resistance of the as-extruded alloys is better than that of the as-homogenized alloys.The superior corrosion resistance of the as-extruded Mg-8Li-3Al-2Zn-0.5Y alloy with the lowest corrosion rate(P_(W)=(0.63±0.26)mm/a)is attributed to the more uniform distribution of second phases,the protectiveα-Mg phase via sacrificing theβ-Li phase and the relatively integrated oxide film.
基金supported by the National Natural Science Foundation of China (Nos. 51674166, U1902220)the National Key R&D Program of China (No. 2021YFB3701303)。
文摘Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.
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Project (50271054) supported by the National Natural Science Foundation of ChinaProject (20070700003) supported by the Doctorate Programs Foundation of Ministry of Education of China+1 种基金Project (102102210031) supported by the Science and Technologies Foundation of Henan Province,ChinaProject (2010A430008) supported by the Natural Science Foundation of Henan Educational Committee of China
文摘Rapidly solidified（RS） Mg-6Zn-1Y-1Ce ribbons were prepared by single roller melt-spinning technique.Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the microstructure of RS ribbons.The results show that there is high density of particles distributed within grains and at grain boundaries in the region near wheel side.The particle density is decreased in the middle region and free surface region.The alloy is predominantly composed of supersaturated--Mg solid solution,T phase and W phase;meanwhile,a few icosahedral quasicrystalline and Mg4Zn7 particles are also observed.The T phase is confirmed having a body-centered orthorhombic structure that is transformed from the body-centered tetragonal structure Mg12Ce phase due to the partial substitution of Mg atoms by Zn.
基金Project(2009AA03Z534) supported by the National Hi-tech Research and Development Program of ChinaProject(2006CB605203) supported by the National Basic Research Program of China
文摘The electromagnetic direct chill （EMDC） casting process is a welt-established production route for aluminum alloy ingot, however, the skin effect restricts the casting diameter. In order to avoid this problem, annulus electromagnetic direct chill （A-EMDC） casting process has been developed. A three-dimension finite element computational model of A-EMDC casting process was established by using ANSYS Magnetic-Nodal programs and FLOTRAN CFD programs. Microstruetures of A-EMDC casting semi-solid Al-6Si-3Cu-Mg alloy billets were investigated. Two pairs of vortexes occur within the crystallizer with opposite direction in A-EMDC. The annulus gap is advantageous to increasing circulate flow, reducing the temperature gradient as well as shallowing liquid sump depth. The microstructure obtained by A-EMDC is globular or rosette-like, and the microstructure is homogeneous in the billet.
基金Funded by the Special Funds of National Space Debris(No.KJSP06211)
文摘The mechanical properties of Al-6Mg alloy with three treatment states （H112, O and cold-extruded states） were investigated at room and high temperatures using an INSTRON machine and a Split Hopkinson Pressure Bar （SHPB）. Stress-strain curves of the alloy with different processes were obtained at a quasi-static strain rate of 5×10-4 s-1and dynamic strain rates of 1 400-4 200 s-1, respectively. The results suggest that, at room temperature, the three processed Al-6Mg alloys are all low sensitive to strain rate. The O state Al-6Mg alloy （Al-6Mg-O） exhibits the most ductility, while the cold-extruded Al-6Mg alloy （Al-6Mg-C） displays the highest strength. At elevated temperatures, the yield stresses and the differences in yield stress of the three processed alloys all decrease with increasing temperature under the quasi-static strain rate of 5×10-4 s-1. Based on test results, modified Johnson-Cook （JC） constitutive models for the three processed Al-6Mg alloys were developed. The microstructures before and after deformation were examined by electron backscattered diffraction （EBSD） and further dynamic recrystallization （DRX） at the strain rate of 3 300 s-1 was discussed.
文摘A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microscopy(SEM),glancing angle X-ray diffractometry(GAXRD) and various electrochemical methods.The micro-arc oxidation process consists of three stages and corresponds with different coating structures.In the initial stage,the coating thickness is linearly increased and is controlled by electrochemical polarization.In the second stage,the coating grows mainly inward and accords with parabolic regularity.In the third stage,the loose coating forms and is controlled by local arc light.The looser coating is mainly composed of MgSiO3 and the compact coating is mainly composed of MgO.From micro-arc oxidation stage to local arc light stage,the corrosion resistance of the coated alloy firstly increases and then decreases.The satisfied corrosion resistance corresponds to the coating time ranging from 6 to10 min.
