Knowledge of the microscopic structure, including three-dimensional （3-D） size and orientation of the precipitates, is essential to fully understand the mechanical properties of the magnesium alloys and designing th...Knowledge of the microscopic structure, including three-dimensional （3-D） size and orientation of the precipitates, is essential to fully understand the mechanical properties of the magnesium alloys and designing the alloys with better performance. Analytical TEM with high spatial resolution offers the simultaneous measurements of 3-D size, structure, orientation, composition of the precipitates from one typical sample along an established crystallographic axis. Besides popular Burgers orientation relationship （OR）, other ORs such as Pitsch-Schrader OR, Crawley OR, Potter OR and a new OR with the form of [0001]α 1.0° from [311]γ and （1120）α 2.0° from （033）γ between the magnesium matrix and the precipitate γ-MglTAl 12 are identified by TEM imaging and diffraction techniques. As a case study, the thicknesses of the individual precipitates with Burgers OR are further measured to be 100 200 nm through both electron energy-loss spectroscopy and x-ray energy dispersive spectroscopy combining differential x-ray absorption and extrapolation, which are in agreement with the overall 3-D size statistic distribution results obtained through analysing various samples along various directions. Furthermore, the fabricated wedge-shape structure provides a platform on which to study the dependence of the interfacial strain on the variation of the thickness.展开更多
Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order （LPSO） structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 2...Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order （LPSO） structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 223 kinds of polytypes of 42R LPSO structure in a hexagonal close-packed （HCP） system, and their stacking sequences and space groups have been derived in detail. The result provides a theoretical explanation for the various polytypes of the LPSO structure.展开更多
文摘本文研究了铸态、固溶态和时效过程的Mg-1.67at.%Zn-2.3at.%Dy与Mg-1.51at.%Zn-2.77at.%Er合金的微观结构变化及其力学性能的影响。微观分析结果表明,Mg-1.67at.%Zn-2.3at.%Dy与Mg-1.51at.%Zn-2.77at.%Er合金,在493 K温度下时效20 h硬度均达到峰值,峰值硬度分别为106.4 HV和98.7 HV。拉伸试验结果表明,固溶处理后,合金Mg-1.67at.%Zn-2.3at.%Dy与Mg-1.51at.%Zn-2.77at.%Er的抗拉强度均有明显的提高。合金Mg-1.67at.%Zn-2.3at.%Dy固溶后包含三个相,分别是α-Mg相,Mg8Zn Dy共晶相,Mg12Zn Dy LPSO相(包括14H型和18R型)。合金Mg-1.51at.%Zn-2.77at.%Er固溶后包含三个相,分别是α-Mg相,Mg3Zn3Er2共晶相,Mg12Zn Er LPSO相(包括14H型和18R型)。
基金Project supported by the National Natural Science Foundation of China (Grant Nos 50571075 and 50771074)the Program for New Century Excellent Talents in University, China (Grant No NCET-07-0640)
文摘Knowledge of the microscopic structure, including three-dimensional （3-D） size and orientation of the precipitates, is essential to fully understand the mechanical properties of the magnesium alloys and designing the alloys with better performance. Analytical TEM with high spatial resolution offers the simultaneous measurements of 3-D size, structure, orientation, composition of the precipitates from one typical sample along an established crystallographic axis. Besides popular Burgers orientation relationship （OR）, other ORs such as Pitsch-Schrader OR, Crawley OR, Potter OR and a new OR with the form of [0001]α 1.0° from [311]γ and （1120）α 2.0° from （033）γ between the magnesium matrix and the precipitate γ-MglTAl 12 are identified by TEM imaging and diffraction techniques. As a case study, the thicknesses of the individual precipitates with Burgers OR are further measured to be 100 200 nm through both electron energy-loss spectroscopy and x-ray energy dispersive spectroscopy combining differential x-ray absorption and extrapolation, which are in agreement with the overall 3-D size statistic distribution results obtained through analysing various samples along various directions. Furthermore, the fabricated wedge-shape structure provides a platform on which to study the dependence of the interfacial strain on the variation of the thickness.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51371130,51171130,and 51271134)the Fundamental Research Funds for the Central Universities,Chinathe Open Research Fund of Science and Technology on High Strength Structural Materials Laboratory,Central South University,China
文摘Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order （LPSO） structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 223 kinds of polytypes of 42R LPSO structure in a hexagonal close-packed （HCP） system, and their stacking sequences and space groups have been derived in detail. The result provides a theoretical explanation for the various polytypes of the LPSO structure.
