The Mg-Li dual-phase alloys, comprised of hexagonal (HCP) and body-centered cubic (BCC) phases, exhibit a better combination of strength and ductility than Mg single-phase alloys. In this work, the deformation behavio...The Mg-Li dual-phase alloys, comprised of hexagonal (HCP) and body-centered cubic (BCC) phases, exhibit a better combination of strength and ductility than Mg single-phase alloys. In this work, the deformation behaviors of Mg-6Li-2Gd and Mg-2Gd alloys, representatives of dual-phase and single-phase alloys, have been studied at both microscale and mesoscale to elucidate the underlying mechanisms. Nanoindentation results show that the α-Mg phase in the Mg-6Li-2Gd alloy is harder than the β-Li phase. The intergranular deformation incompatibility, which arises from the elastic-plastic interactions, different strain accommodation behaviors, and strain hardening behaviors between the hard α-Mg phase and the soft β-Li phase, leads to pronounced hetero-deformation induced (HDI) stress of the Mg-6Li-2Gd alloy. The HDI stress strengthens the two phases simultaneously, so that the yield strength of the dual-phase Mg-6Li-2Gd alloy is higher than the Mg-2Gd alloy as well as the harder α-Mg phase in the Mg-6Li-2Gd alloy. Due to the decreased strength difference between the two phases caused by the HDI stress strengthening, the dual-phase alloy exhibits homogeneous plasticity at the mesoscale, which benefits the elongation of the Mg-6Li-2Gd alloy. The HDI strengthening magnitude in the Mg-6Li-2Gd alloy is further quantified. Based on the equal strain upper bound and equal stress lower bound approximations, the yield strength improved by the HDI stress is estimated to be 18–37 MPa, which is in the same range as the elastic visco-plastic self-consistent (EVPSC) simulation results. As the tensile strain is larger than ∼3 %, the HDI strengthening magnitude for the Mg-6Li-2Gd alloy reaches 50–65 MPa, accounting for 35 % of the corresponding flow stress.展开更多
Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was ...Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was analyzed by X-ray diffraction （XRD）, optical microscopy （OM） and scanning electron microscopy （SEM）. The results show that magnesium and gadolinium deposit mainly in the first 30 min, and the alloy obtained contains 96.53% Mg, 0.27% Li and 3.20% Gd （mass fraction）. Then, the reduction of lithium ions occurs quickly. The composition of alloy can be adjusted by controlling electrolysis time or Gd 2 O 3 concentration in LiCl-KCl melts. With the addition of Gd into Mg-Li alloys, the corrosion resistance of the alloys is enhanced. XRD results suggest that Mg 3 Gd and Mg 2 Gd can be formed in Mg-Li-Gd alloys. The distribution of Gd element in Mg-Li-Gd alloys indicates that Gd element mainly distributes at the grain boundaries of Mg-Li-Gd alloys.展开更多
The as-cast Mg-8 Li-xZn-yGd(x=1 2, 3,4;y=1,2;wt.%)alloys were prepared in a vacuum induction furnace and their microstructure and mechanical properties were investigated. The results show that the increase of Zn conte...The as-cast Mg-8 Li-xZn-yGd(x=1 2, 3,4;y=1,2;wt.%)alloys were prepared in a vacuum induction furnace and their microstructure and mechanical properties were investigated. The results show that the increase of Zn content results in the volume fraction of W-phase(Mg3 Zn3 Gd2) increasing while that of Mg3 Gd phase decreasing. The strength of Mg-8 Li-xZn-1 Gd alloys is improved with the increase of Zn content,which is ascribed to the second phase strengthening of fine strip-like W-phase and the solid solution strengthening of Zn element.For Mg-8 Li-4 Zn-yGd alloys,the increase of Gd content leads to the appearance of coarse and discontinuous net-like W-phase, which decreases the strength. The Mg-8 Li-4 Zn-1 Gd alloy exhibits an optimum comprehensive performance with the yield strength, ultimate tensile strength and elongation of 154.7 MPa, 197.0 MPa and 12.4%, respectively. In addition,the aging behavior of the typical alloys was also investigated.展开更多
The microstructure observation,tensile test,electrochemical measurement,and corrosion morphology characterization were conducted to study the effect of Gd on the microstructure,mechanical properties,and corrosion beha...The microstructure observation,tensile test,electrochemical measurement,and corrosion morphology characterization were conducted to study the effect of Gd on the microstructure,mechanical properties,and corrosion behavior of as-homogenized Mg−8Li−3Al−2Zn−0.2Zr(LAZ832−0.2Zr)alloy.The addition of trace Gd can improve the mechanical properties of as-homogenized LAZ832−0.2Zr alloy by refining the microstructure,reducing the content of AlLi softening phase,and forming Al_(2)Gd strengthening phase.Meanwhile,the addition of trace Gd can weaken the microgalvanic corrosion between matrix phase and AlLi phase,inhibit the galvanic corrosion betweenα-Mg phase andβ-Li phase,and result in the formation of dense oxide film containing Gd_(2)O_(3),thereby improving the corrosion resistance of the alloy.When the Gd content is 1.0 wt.%,the alloy shows the best comprehensive properties with the ultimate tensile strength of 189.8 MPa,elongation of 42.3%,and corrosion rate(determined by hydrogen evolution)of 0.86 mm·a^(−1).展开更多
基金support from the National Natural Science Foundation of China(Grant Nos.52071206,U2241231,and 52305506).
文摘The Mg-Li dual-phase alloys, comprised of hexagonal (HCP) and body-centered cubic (BCC) phases, exhibit a better combination of strength and ductility than Mg single-phase alloys. In this work, the deformation behaviors of Mg-6Li-2Gd and Mg-2Gd alloys, representatives of dual-phase and single-phase alloys, have been studied at both microscale and mesoscale to elucidate the underlying mechanisms. Nanoindentation results show that the α-Mg phase in the Mg-6Li-2Gd alloy is harder than the β-Li phase. The intergranular deformation incompatibility, which arises from the elastic-plastic interactions, different strain accommodation behaviors, and strain hardening behaviors between the hard α-Mg phase and the soft β-Li phase, leads to pronounced hetero-deformation induced (HDI) stress of the Mg-6Li-2Gd alloy. The HDI stress strengthens the two phases simultaneously, so that the yield strength of the dual-phase Mg-6Li-2Gd alloy is higher than the Mg-2Gd alloy as well as the harder α-Mg phase in the Mg-6Li-2Gd alloy. Due to the decreased strength difference between the two phases caused by the HDI stress strengthening, the dual-phase alloy exhibits homogeneous plasticity at the mesoscale, which benefits the elongation of the Mg-6Li-2Gd alloy. The HDI strengthening magnitude in the Mg-6Li-2Gd alloy is further quantified. Based on the equal strain upper bound and equal stress lower bound approximations, the yield strength improved by the HDI stress is estimated to be 18–37 MPa, which is in the same range as the elastic visco-plastic self-consistent (EVPSC) simulation results. As the tensile strain is larger than ∼3 %, the HDI strengthening magnitude for the Mg-6Li-2Gd alloy reaches 50–65 MPa, accounting for 35 % of the corresponding flow stress.
基金Project(2009AA050702)supported by the National High-tech Research and Development Program of ChinaProject(GC06A212)supported by the Scientific Technology Project of Heilongjiang Province,China+2 种基金Project(50871033)supported by the National Natural Science Foundation of ChinaProject(208181)supported by the Key Project of Ministry of Education,ChinaProject(HEUCF101002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was analyzed by X-ray diffraction （XRD）, optical microscopy （OM） and scanning electron microscopy （SEM）. The results show that magnesium and gadolinium deposit mainly in the first 30 min, and the alloy obtained contains 96.53% Mg, 0.27% Li and 3.20% Gd （mass fraction）. Then, the reduction of lithium ions occurs quickly. The composition of alloy can be adjusted by controlling electrolysis time or Gd 2 O 3 concentration in LiCl-KCl melts. With the addition of Gd into Mg-Li alloys, the corrosion resistance of the alloys is enhanced. XRD results suggest that Mg 3 Gd and Mg 2 Gd can be formed in Mg-Li-Gd alloys. The distribution of Gd element in Mg-Li-Gd alloys indicates that Gd element mainly distributes at the grain boundaries of Mg-Li-Gd 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
文摘The as-cast Mg-8 Li-xZn-yGd(x=1 2, 3,4;y=1,2;wt.%)alloys were prepared in a vacuum induction furnace and their microstructure and mechanical properties were investigated. The results show that the increase of Zn content results in the volume fraction of W-phase(Mg3 Zn3 Gd2) increasing while that of Mg3 Gd phase decreasing. The strength of Mg-8 Li-xZn-1 Gd alloys is improved with the increase of Zn content,which is ascribed to the second phase strengthening of fine strip-like W-phase and the solid solution strengthening of Zn element.For Mg-8 Li-4 Zn-yGd alloys,the increase of Gd content leads to the appearance of coarse and discontinuous net-like W-phase, which decreases the strength. The Mg-8 Li-4 Zn-1 Gd alloy exhibits an optimum comprehensive performance with the yield strength, ultimate tensile strength and elongation of 154.7 MPa, 197.0 MPa and 12.4%, respectively. In addition,the aging behavior of the typical alloys was also investigated.
基金financial supports from the Anhui Provincial Natural Science Foundation,China (No.2208085QE124)the Natural Science Foundation of the Education Department of Anhui Province,China (No.KJ2021A0394)the Open Project of Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials,China (No.GFST2021KF04)。
文摘The microstructure observation,tensile test,electrochemical measurement,and corrosion morphology characterization were conducted to study the effect of Gd on the microstructure,mechanical properties,and corrosion behavior of as-homogenized Mg−8Li−3Al−2Zn−0.2Zr(LAZ832−0.2Zr)alloy.The addition of trace Gd can improve the mechanical properties of as-homogenized LAZ832−0.2Zr alloy by refining the microstructure,reducing the content of AlLi softening phase,and forming Al_(2)Gd strengthening phase.Meanwhile,the addition of trace Gd can weaken the microgalvanic corrosion between matrix phase and AlLi phase,inhibit the galvanic corrosion betweenα-Mg phase andβ-Li phase,and result in the formation of dense oxide film containing Gd_(2)O_(3),thereby improving the corrosion resistance of the alloy.When the Gd content is 1.0 wt.%,the alloy shows the best comprehensive properties with the ultimate tensile strength of 189.8 MPa,elongation of 42.3%,and corrosion rate(determined by hydrogen evolution)of 0.86 mm·a^(−1).
