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
Machined chips of Mg-Zn-Y-Zr alloy were consolidated by cold pressing and then hot extrusion under various processing temperatures and extrusion ratios. The results show that the microstructure of the chip-extruded al...Machined chips of Mg-Zn-Y-Zr alloy were consolidated by cold pressing and then hot extrusion under various processing temperatures and extrusion ratios. The results show that the microstructure of the chip-extruded alloy is marked by a large number of recrystallized grains and some unrecrystallized grains, which results in high strength but low ductility at temperatures below 320 ℃. With increasing processing temperature up to 360 ℃, entirely recrystallized and equiaxed grains are obtained. Mg-Zn-Y-Zr alloy with low strength but high ductility is obtained compared with the alloy processed at low temperature. At 420℃, coarse and equiaxed grains are formed, which results in the drastic decrease of mechanical properties. With increasing extrusion ratio from 8 to 16, the grain refinement is more obvious and the mechanical properties at room temperature are improved effectively. However, the yield strength and ultimate tensile strength are improved a little with further increasing extrusion ratio.展开更多
The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^＋-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties ...The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^＋-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_（HRS）/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current（SCLC）.The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.展开更多
The structure and chemical durability of non-alkali aluminoborosilicate glasses with various contents of ZnO were investigated.As the replacement of MgO by ZnO increases from 0 to 3.2mol%,the average number of bridge ...The structure and chemical durability of non-alkali aluminoborosilicate glasses with various contents of ZnO were investigated.As the replacement of MgO by ZnO increases from 0 to 3.2mol%,the average number of bridge oxygen per tetrahedron (BO/T) as a measure of network connectivity increases from 2.84 to 3.04,and the chemical durability improved.The weight loss ratio (WLR) of glass etched in 10vol% HF (20 ℃,20 min) solution decreased from 4.809 to 4.509,and in 5wt% NaOH (95 ℃,6 h) solution decreased from 1.201 to 0.994.The replacement of MgO by ZnO further increased to 6.4mol%,the value of BO/T decreased to 3.04 instead,and thus the chemical durability deteriorated.The WLR of HF-acid and NaOH-alkali corrosion increased to 6.683 and 1.994,respectively.The chemical durability shows strongly dependent on the network connectivity and exhibits mixed intermediate effects during the replacement of MgO by ZnO.展开更多
The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150℃have been investigated by using tensile tests,optical metallography,scanning electron microscopy,transmission ...The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150℃have been investigated by using tensile tests,optical metallography,scanning electron microscopy,transmission electron microscopy and atom probe tomography analyses.With increasing Zn/Mg ratios,the ageing process is significantly accelerated and the time to peak ageing is reduced.T’phase predominates in alloys of lower Zn/Mg ratios whileη’phase predominates in alloys with a Zn/Mg ratio over 2.86.Co-existence of T’phase andη’phase with a large number density is beneficial to the high strength of alloys.Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture.A strength model has been established to predict the co-strengthening effect of T’phase andη’phase in Al-Zn-Mg-Cu alloys,including the factors of the grain boundary,solid solution and precipitation.展开更多
Al-Zn-Mg-Cu alloys with different major strengthening precipitates are subjected to a novel combinatorial pre-treatment,including natural ageing and pre-stretching.The evolution of hardness and microstructure during t...Al-Zn-Mg-Cu alloys with different major strengthening precipitates are subjected to a novel combinatorial pre-treatment,including natural ageing and pre-stretching.The evolution of hardness and microstructure during the combinatorial pre-treatment and subsequent artificial ageing has been investigated.The results reveal that the growth rate of hardness in alloy B(Zn/Mg=10.0)is much higher than that of alloy A(Zn/Mg=1.5)due to the fast precipitation kinetics ofηphase compared with T phase.Both GP I zones and dislocations introduced by the combinatorial pre-treatment can act as heterogeneous nucleation sites for precipitation,resulting in more precipitates and higher hardness than pre-stretched alloys A and B.Dislocations distribute uniformly in combinatorial pre-treated alloys owing to the existence of GP I zones and dislocations,which promote the precipitation and refine the precipitate size.Moreover,these alloys with distinct pre-stretching(2%–10%)show similar precipitation behavior and peak hardness,and it indicates that the dislocation-induced precipitation will not be affected by the density of dislocations when plenty of GP I zones pre-exist.展开更多
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 (51005217) supported by the National Natural Science Foundation of ChinaProject (20100480677) supported by China Postdoctoral Science Foundation
文摘Machined chips of Mg-Zn-Y-Zr alloy were consolidated by cold pressing and then hot extrusion under various processing temperatures and extrusion ratios. The results show that the microstructure of the chip-extruded alloy is marked by a large number of recrystallized grains and some unrecrystallized grains, which results in high strength but low ductility at temperatures below 320 ℃. With increasing processing temperature up to 360 ℃, entirely recrystallized and equiaxed grains are obtained. Mg-Zn-Y-Zr alloy with low strength but high ductility is obtained compared with the alloy processed at low temperature. At 420℃, coarse and equiaxed grains are formed, which results in the drastic decrease of mechanical properties. With increasing extrusion ratio from 8 to 16, the grain refinement is more obvious and the mechanical properties at room temperature are improved effectively. However, the yield strength and ultimate tensile strength are improved a little with further increasing extrusion ratio.
基金Funded by the National Natural Science Foundation of China(No.51262003)the Guangxi Key Laboratory of Information Materials(Guilin University of Electronic Technology),China(No.1110908-10-Z)
文摘The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^＋-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_（HRS）/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current（SCLC）.The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.
基金the Nation Key Research and Development Program of China(No.2016YFB0303700)the Hubei Provincial Major Technical Innovation Program of China(No.2017AAA117)the National Natural Science foundation of China(No.51602235)。
文摘The structure and chemical durability of non-alkali aluminoborosilicate glasses with various contents of ZnO were investigated.As the replacement of MgO by ZnO increases from 0 to 3.2mol%,the average number of bridge oxygen per tetrahedron (BO/T) as a measure of network connectivity increases from 2.84 to 3.04,and the chemical durability improved.The weight loss ratio (WLR) of glass etched in 10vol% HF (20 ℃,20 min) solution decreased from 4.809 to 4.509,and in 5wt% NaOH (95 ℃,6 h) solution decreased from 1.201 to 0.994.The replacement of MgO by ZnO further increased to 6.4mol%,the value of BO/T decreased to 3.04 instead,and thus the chemical durability deteriorated.The WLR of HF-acid and NaOH-alkali corrosion increased to 6.683 and 1.994,respectively.The chemical durability shows strongly dependent on the network connectivity and exhibits mixed intermediate effects during the replacement of MgO by ZnO.
基金supported by the National Natural Science Foundation of China(No.51871033)the National Key Research and Development Program of China(2016YFB0700401)the Opening Project of State Key Laboratory for Advanced Metals and Materials(No.2020-ZD02)。
文摘The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150℃have been investigated by using tensile tests,optical metallography,scanning electron microscopy,transmission electron microscopy and atom probe tomography analyses.With increasing Zn/Mg ratios,the ageing process is significantly accelerated and the time to peak ageing is reduced.T’phase predominates in alloys of lower Zn/Mg ratios whileη’phase predominates in alloys with a Zn/Mg ratio over 2.86.Co-existence of T’phase andη’phase with a large number density is beneficial to the high strength of alloys.Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture.A strength model has been established to predict the co-strengthening effect of T’phase andη’phase in Al-Zn-Mg-Cu alloys,including the factors of the grain boundary,solid solution and precipitation.
基金supported by the National Natural Science Foundation of China(No.51871033)the Opening Project of the State Key Laboratory for Advanced Metals and Materials(Nos.2020-ZD02 and 2022-Z03).
文摘Al-Zn-Mg-Cu alloys with different major strengthening precipitates are subjected to a novel combinatorial pre-treatment,including natural ageing and pre-stretching.The evolution of hardness and microstructure during the combinatorial pre-treatment and subsequent artificial ageing has been investigated.The results reveal that the growth rate of hardness in alloy B(Zn/Mg=10.0)is much higher than that of alloy A(Zn/Mg=1.5)due to the fast precipitation kinetics ofηphase compared with T phase.Both GP I zones and dislocations introduced by the combinatorial pre-treatment can act as heterogeneous nucleation sites for precipitation,resulting in more precipitates and higher hardness than pre-stretched alloys A and B.Dislocations distribute uniformly in combinatorial pre-treated alloys owing to the existence of GP I zones and dislocations,which promote the precipitation and refine the precipitate size.Moreover,these alloys with distinct pre-stretching(2%–10%)show similar precipitation behavior and peak hardness,and it indicates that the dislocation-induced precipitation will not be affected by the density of dislocations when plenty of GP I zones pre-exist.
