The Mg_(17)Al_(12)-phase,which is common and important in Mg-Al alloy,has long been regarded as a brittle phase in experiments but theoretical calculations report controversial results.To unravel why theoretical calcu...The Mg_(17)Al_(12)-phase,which is common and important in Mg-Al alloy,has long been regarded as a brittle phase in experiments but theoretical calculations report controversial results.To unravel why theoretical calculations report controversial results and determine whether Mg_(17)Al_(12)is brittle or ductile,density functional theory calculations on atomic level are performed to investigate mechanic properties of Mg_(17)Al_(12)without containing alloying elements and without taking the size effect.The results showed that the parameter k-point played critical role in the DFT-based elastic calculations.The convergent G/B ratio of Mg_(17)Al_(12)was about 0.52,suggesting that the Mg_(17)Al_(12)-phase was theoretically ductile although its ductility was poor.The chemical bonding in Mg_(17)Al_(12)was the mixture of metallic Mg-Mg bond and covalent Al-Al bond.The advantage of metallic bonding over covalent bonding provided a possible explanation for the ductility of Mg_(17)Al_(12).Possible reasons for the brittleness of Mg_(17)Al_(12)in experiments are also discussed.展开更多
By using CaCO3 as the "blowing agent", Zn–(10–50) wt% Mg alloy foams with close-pore structure were fabricated by the powder metallurgical route. The key of successful foaming is Mg addition and the proper sinte...By using CaCO3 as the "blowing agent", Zn–(10–50) wt% Mg alloy foams with close-pore structure were fabricated by the powder metallurgical route. The key of successful foaming is Mg addition and the proper sintering treatment, which lead to the formation of intermetallic compounds and can make the gas release reaction between Mg melt and CaCO3 happen the during foaming process.展开更多
A commercial as-cast ME21 magnesium alloy containing rare-earth (RE) element was processed by equalchannel angular pressing to obtain fine-grained micro structure. Stress corrosion cracking (SCC) behaviors of the fine...A commercial as-cast ME21 magnesium alloy containing rare-earth (RE) element was processed by equalchannel angular pressing to obtain fine-grained micro structure. Stress corrosion cracking (SCC) behaviors of the fine-grained samples were studied by slow-strain-rate testing in air, distilled water and Hanks’solution at the strain rate of 1×10^(-6) s^(-1). All samples show a relatively low SCC sensitivity in distilled water but a great SCC tendency in Hanks’ solution. The microscopic observations of the fracture surfaces and the side surfaces reveal obvious active anodic dissolution and hydrogen embrittlement cracks, which indicate the higher SCC susceptibility in Hanks'solution. The fine-grained microstructure with more crystal defects promotes the passivation process of the oxide film and restrains the hydrogen induced cracking of the ME21 magnesium alloy, leading to the higher general corrosion resistance as well as SCC resistance.展开更多
The gas released from the titanium hydride decomposition is one of the key factors to influence the Al alloy melt foaming process.In this study,a set of decomposition kinetic equations of titanium hydride was acquired...The gas released from the titanium hydride decomposition is one of the key factors to influence the Al alloy melt foaming process.In this study,a set of decomposition kinetic equations of titanium hydride was acquired by separating its temperature programmed decomposition(TPD) spectrum,which was acquired by a special designed TPD apparatus with argon used as carrier gas and thermal conductivity cell as the detector.According to these equations,the decomposition and hydrogen release characteristics of titanium hydride at a fixed/elevated temperature are described quantitatively,which can be applied to forecast the Al alloy melt foaming process and furnish the theoretical basis for fabrication of three-dimensional complex shaped Al alloy foam.展开更多
基金supported by National Natural Science Foundation of China(Grant No.51878246,51975183)
文摘The Mg_(17)Al_(12)-phase,which is common and important in Mg-Al alloy,has long been regarded as a brittle phase in experiments but theoretical calculations report controversial results.To unravel why theoretical calculations report controversial results and determine whether Mg_(17)Al_(12)is brittle or ductile,density functional theory calculations on atomic level are performed to investigate mechanic properties of Mg_(17)Al_(12)without containing alloying elements and without taking the size effect.The results showed that the parameter k-point played critical role in the DFT-based elastic calculations.The convergent G/B ratio of Mg_(17)Al_(12)was about 0.52,suggesting that the Mg_(17)Al_(12)-phase was theoretically ductile although its ductility was poor.The chemical bonding in Mg_(17)Al_(12)was the mixture of metallic Mg-Mg bond and covalent Al-Al bond.The advantage of metallic bonding over covalent bonding provided a possible explanation for the ductility of Mg_(17)Al_(12).Possible reasons for the brittleness of Mg_(17)Al_(12)in experiments are also discussed.
基金supported by the Research Project of University of Science and Technology Beijing (USTB) (Grant No. 2015-Z06)the Fundamental Research Funds for the Central Universities (Grant No. 2016B06614)National Natural Science Foundation of China (No. 11472098)
文摘By using CaCO3 as the "blowing agent", Zn–(10–50) wt% Mg alloy foams with close-pore structure were fabricated by the powder metallurgical route. The key of successful foaming is Mg addition and the proper sintering treatment, which lead to the formation of intermetallic compounds and can make the gas release reaction between Mg melt and CaCO3 happen the during foaming process.
基金supported by the Key Research and Development Project of Jiangsu Province of China(BE2017148)the Fundamental Research Funds for the Central Universities(HHU2016B10314)Six Major Talent Peaks Project of Jiangsu Province of China(2014-XCL-023)
文摘A commercial as-cast ME21 magnesium alloy containing rare-earth (RE) element was processed by equalchannel angular pressing to obtain fine-grained micro structure. Stress corrosion cracking (SCC) behaviors of the fine-grained samples were studied by slow-strain-rate testing in air, distilled water and Hanks’solution at the strain rate of 1×10^(-6) s^(-1). All samples show a relatively low SCC sensitivity in distilled water but a great SCC tendency in Hanks’ solution. The microscopic observations of the fracture surfaces and the side surfaces reveal obvious active anodic dissolution and hydrogen embrittlement cracks, which indicate the higher SCC susceptibility in Hanks'solution. The fine-grained microstructure with more crystal defects promotes the passivation process of the oxide film and restrains the hydrogen induced cracking of the ME21 magnesium alloy, leading to the higher general corrosion resistance as well as SCC resistance.
基金supported by the Supporting Program for Science and Technology of Changzhou(Industry,Grant No.CE20120024)National Natural Science Foundation of China(Grant No.11472098)+3 种基金the financial support from111 Project(No.B07003)the Program for Changjiang Scholars and Innovative Research Team in Universitythe Research Project of State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology Beijing(SKL-AMM-USTB)(Grant No.2011Z-13)
文摘The gas released from the titanium hydride decomposition is one of the key factors to influence the Al alloy melt foaming process.In this study,a set of decomposition kinetic equations of titanium hydride was acquired by separating its temperature programmed decomposition(TPD) spectrum,which was acquired by a special designed TPD apparatus with argon used as carrier gas and thermal conductivity cell as the detector.According to these equations,the decomposition and hydrogen release characteristics of titanium hydride at a fixed/elevated temperature are described quantitatively,which can be applied to forecast the Al alloy melt foaming process and furnish the theoretical basis for fabrication of three-dimensional complex shaped Al alloy foam.