High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-p...High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.展开更多
The magnesium alloy is prone to burn during die-casting, which limits its applications severely, so the effect of adding rare earth （RE） on the ignition-proof of AZ91D Mg alloy is studied. The results indicate that ...The magnesium alloy is prone to burn during die-casting, which limits its applications severely, so the effect of adding rare earth （RE） on the ignition-proof of AZ91D Mg alloy is studied. The results indicate that the addition of mischmetal RE elements has a remarkable influence on the ignition-proof property of the magnesium alloy. It is found that the ignition temperature of the magnesium alloy can be greatly raised by adding a proper amount of RE. When the amount is 0.1wt%, the ignition temperature reaches 877℃ which is 206℃ higher than that of AZ91D without RE and the mechanical properties of the alloy are also improved, However, the amount of RE must be properly controlled because too much RE would induce grain coarsening and reduce the mechanical properties.展开更多
Theoretical analysis on ignition-proof of AZ91D alloy added with Ce was studied. The effect of Ce on burning temperature was investigated. The burning temperature increases with increasing Ce by insulation work at dif...Theoretical analysis on ignition-proof of AZ91D alloy added with Ce was studied. The effect of Ce on burning temperature was investigated. The burning temperature increases with increasing Ce by insulation work at different temperatures. The influence of Ce on maximum insulation work time was also studied. The maximum insulation work time increases with increasing Ce and decreases with the melting temperature. There is a tendency for Ce to concentrate on the surface of melti.ng AZ91D alloy. Ce will react with MgO and O2. The resultant will fill the cavity of MgO film to form multifilm. So the density of surface film of liquid Mg will increase to prevent burning.展开更多
The ignition-proof mechanism of ZM5 magnesium alloy added with 0.1% （mass fraction） rare earth （RE） was investigated. The oxide scales and substrates were characterized by scanning electronic microscope （SEM）, X...The ignition-proof mechanism of ZM5 magnesium alloy added with 0.1% （mass fraction） rare earth （RE） was investigated. The oxide scales and substrates were characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, energy dispersive spectrometer （EDS） and tensile test. And an oxidation model of ZM5 alloy with RE was established. The results show that the ignition temperature of ZM5 alloy is particularly elevated from 654 to 823 ℃, the microstructure is refined, and the tensile strength is slightly improved from 168.2 to 174.6 MPa by adding 0.1% RE. A double-layer oxidation film formed on the alloy surface under high temperature mainly consists of MgO, RE203 and A1203, which is 2.5-3.5 μm in thickness. It is found that the forming of protective oxidation film on the thermodynamics is attributed to RE elements congregating on the surface of molten Mg alloy.展开更多
This study focused on the synergistic effect of alloying elements neodymium(Nd) and dysprosium(Dy) on the ignition-proof performance of AZ91D alloy. The ignition-proof mechanism of AZ91D-3 Nd-x Dy(x = 0.5, 1.0, 1.5, 2...This study focused on the synergistic effect of alloying elements neodymium(Nd) and dysprosium(Dy) on the ignition-proof performance of AZ91D alloy. The ignition-proof mechanism of AZ91D-3 Nd-x Dy(x = 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%) alloy was discussed in depth through ignition-proof testing and microstructure observation. The results showed that the AZ91D-3 Nd-2 Dy alloy exhibited the highest ignition-point of 893 K, increased by 69 K as compared to the AZ91D alloy. The ignition-proof mechanism of Nd and Dy additions lay in three aspects:(1) the formation of denser oxide film consisting of Dy_2O_3 and MgO improves the oxidation resistance of the alloy,(2) the great reduction of the low melting-point phase β-Mg_(17)Al_(12), which leads to the decrease in the oxygen diffusion channels, and(3) the newly formed high melting-point phases(Al_2Nd and Al_2Dy), which block the oxygen diffusion channels and prevent the chemical reaction of Mg and oxygen.展开更多
The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that...The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that La atoms preferred occupying surface sites to the bulk sites, which suggested the La surface segregation. When oxygen atoms adsorbed on a pure or La alloyed Mg （0001） surface, certain amount of heat would release, and La alloying made the heat released less, which might increase the ignition point of Mg alloy. Both Mg and La had strong atomic affinity with oxygen, so the oxidation film of Mg-La alloys consisted of MgO, La2O3. The denser La2O3 turned oxide film into free and close structure, and prevented oxygen from passing through the oxidation film. The La-O covalent bonding could explain why La2O3 was compact, and resulted in good ignition-proof of Mg-La alloys.展开更多
A Mg-Y-Ca-Ce magnesium alloy was optimized for high ignition-proof property, which did not bum in air at 1233 K up to 30 min. Oxidation behavior of the alloy was investigated by X-ray diffraction （XRD）, scanning ele...A Mg-Y-Ca-Ce magnesium alloy was optimized for high ignition-proof property, which did not bum in air at 1233 K up to 30 min. Oxidation behavior of the alloy was investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and thermodynamics calculation at 673, 773 and 873 K. XRD and SEM analysis indicated that dense and compact oxide films composed of MgO, Y203 and CaO formed. The oxidation behavior was characterized by the selective oxidation. Based on Pilling-Bedworth ra- tio （PBR） and energy dispersive spectrometer （EDS） analysis, Y203 contributed more to form the compact surface oxide film, which led to the excellent ignition-proof performance. The thermodynamics analysis and EDS results implied that the Y-rich areas were preferred paths for the selective oxidation.展开更多
Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca,which could be melted at 1173 K in air without any protection.Thermogravimetric measurements in dr...Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca,which could be melted at 1173 K in air without any protection.Thermogravimetric measurements in dry air revealed that the oxidation dynamics curves of Mg-2.5Ca alloy and Mg-3.5Y-0.79Ca alloy at high temperatures followed the parabolic-line law or the cubic-line law.X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis indicated that the oxide film on the surface of Mg-3.5Y-0.79Ca and Mg-2.5Ca alloys exhibited a duplex structure,which agreed with the results of thermodynamic analysis.By comparison,the ignition-proof effect of the combination addition of Y and Ca was better than that of the single addition of Ca.展开更多
基金the financial supports from the National Key Research and Development Plan(Grant No.2021YFB3701100)the National Natural Science Foundation of China(Grant No.U2241231,No.52071206)。
文摘High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.
文摘The magnesium alloy is prone to burn during die-casting, which limits its applications severely, so the effect of adding rare earth （RE） on the ignition-proof of AZ91D Mg alloy is studied. The results indicate that the addition of mischmetal RE elements has a remarkable influence on the ignition-proof property of the magnesium alloy. It is found that the ignition temperature of the magnesium alloy can be greatly raised by adding a proper amount of RE. When the amount is 0.1wt%, the ignition temperature reaches 877℃ which is 206℃ higher than that of AZ91D without RE and the mechanical properties of the alloy are also improved, However, the amount of RE must be properly controlled because too much RE would induce grain coarsening and reduce the mechanical properties.
文摘Theoretical analysis on ignition-proof of AZ91D alloy added with Ce was studied. The effect of Ce on burning temperature was investigated. The burning temperature increases with increasing Ce by insulation work at different temperatures. The influence of Ce on maximum insulation work time was also studied. The maximum insulation work time increases with increasing Ce and decreases with the melting temperature. There is a tendency for Ce to concentrate on the surface of melti.ng AZ91D alloy. Ce will react with MgO and O2. The resultant will fill the cavity of MgO film to form multifilm. So the density of surface film of liquid Mg will increase to prevent burning.
基金Project(2004BB8429) supported by Chongqing Municipal Science and Technology Commission, China
文摘The ignition-proof mechanism of ZM5 magnesium alloy added with 0.1% （mass fraction） rare earth （RE） was investigated. The oxide scales and substrates were characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, energy dispersive spectrometer （EDS） and tensile test. And an oxidation model of ZM5 alloy with RE was established. The results show that the ignition temperature of ZM5 alloy is particularly elevated from 654 to 823 ℃, the microstructure is refined, and the tensile strength is slightly improved from 168.2 to 174.6 MPa by adding 0.1% RE. A double-layer oxidation film formed on the alloy surface under high temperature mainly consists of MgO, RE203 and A1203, which is 2.5-3.5 μm in thickness. It is found that the forming of protective oxidation film on the thermodynamics is attributed to RE elements congregating on the surface of molten Mg alloy.
文摘This study focused on the synergistic effect of alloying elements neodymium(Nd) and dysprosium(Dy) on the ignition-proof performance of AZ91D alloy. The ignition-proof mechanism of AZ91D-3 Nd-x Dy(x = 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%) alloy was discussed in depth through ignition-proof testing and microstructure observation. The results showed that the AZ91D-3 Nd-2 Dy alloy exhibited the highest ignition-point of 893 K, increased by 69 K as compared to the AZ91D alloy. The ignition-proof mechanism of Nd and Dy additions lay in three aspects:(1) the formation of denser oxide film consisting of Dy_2O_3 and MgO improves the oxidation resistance of the alloy,(2) the great reduction of the low melting-point phase β-Mg_(17)Al_(12), which leads to the decrease in the oxygen diffusion channels, and(3) the newly formed high melting-point phases(Al_2Nd and Al_2Dy), which block the oxygen diffusion channels and prevent the chemical reaction of Mg and oxygen.
基金National Natural Science Foundation of China(50671069)Natural Science Foundation of Liaoning Province(20102173)the Experimental Central Director’s Foundation of Shenyang Normal University(Sy201103)
文摘The surface segregation of La and its effect on the oxygen adsorption on a Mg （0001） surface for a coverage 0=-0.25 monolayer were performed by using first-principles calculations. The calculated results showed that La atoms preferred occupying surface sites to the bulk sites, which suggested the La surface segregation. When oxygen atoms adsorbed on a pure or La alloyed Mg （0001） surface, certain amount of heat would release, and La alloying made the heat released less, which might increase the ignition point of Mg alloy. Both Mg and La had strong atomic affinity with oxygen, so the oxidation film of Mg-La alloys consisted of MgO, La2O3. The denser La2O3 turned oxide film into free and close structure, and prevented oxygen from passing through the oxidation film. The La-O covalent bonding could explain why La2O3 was compact, and resulted in good ignition-proof of Mg-La alloys.
基金Project supported by the National Key Technology R&D Program(2011BAE22B06)National Natural Science Foundation of China(51101100)
文摘A Mg-Y-Ca-Ce magnesium alloy was optimized for high ignition-proof property, which did not bum in air at 1233 K up to 30 min. Oxidation behavior of the alloy was investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and thermodynamics calculation at 673, 773 and 873 K. XRD and SEM analysis indicated that dense and compact oxide films composed of MgO, Y203 and CaO formed. The oxidation behavior was characterized by the selective oxidation. Based on Pilling-Bedworth ra- tio （PBR） and energy dispersive spectrometer （EDS） analysis, Y203 contributed more to form the compact surface oxide film, which led to the excellent ignition-proof performance. The thermodynamics analysis and EDS results implied that the Y-rich areas were preferred paths for the selective oxidation.
基金supported by National Natural Science Foundation of China (50901048)the fund of the State Key Laboratory of Solidification Process-ing in NWPU (SKLSP201003)+2 种基金Program for Changjiang Scholar and Innovative Research Team in University (IRT0972)Program for the TopYoung Academic Leaders of Higher Learning Institutions of ShanxiNatural Science Foundation of Shanxi (2010021022-5)
文摘Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca,which could be melted at 1173 K in air without any protection.Thermogravimetric measurements in dry air revealed that the oxidation dynamics curves of Mg-2.5Ca alloy and Mg-3.5Y-0.79Ca alloy at high temperatures followed the parabolic-line law or the cubic-line law.X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis indicated that the oxide film on the surface of Mg-3.5Y-0.79Ca and Mg-2.5Ca alloys exhibited a duplex structure,which agreed with the results of thermodynamic analysis.By comparison,the ignition-proof effect of the combination addition of Y and Ca was better than that of the single addition of Ca.
