Zhifeng Wang Weimin Zhao Haipeng Li Jian Ding Yongyan Li Chunyong Liang
材料科学技术（英）
For the first time, petal-like and spherical Mg-based icosahedral quasicrystal phase (I-phase) were obtained by introducing Ti, Sb, Ce and C nanotubes into Mg-Zn-Y alloy under normal casting conditions. The formation mechanism and stability criterion of spherical I-phase were discussed. The morphology and microhardness of I-phase and their determinants were studied in this paper. The results show that the different value of microhardness of I-phase could be attributed to the different kinds of the fourth component and its content, and its different innate characters. The final morphology of icosahedral quasicrystalline (IQC) is decided by the size of critical stable radius Rr, the content of the fourth component and degree of undercooling.
关键词:
Quasicrystal
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Xiying ZHOU
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Peiyao LI
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Junming LUO
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Shiqiang QIAN
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Jianhua TONG
材料科学技术（英）
Dry sliding friction between the Al¬59Cu¬25.5Fe¬12.5B¬3 quasicrystals (QCs)/coating of the diamond-like carbon (DLC) was carried out by self-made tribometer under different conditions. The influences of four parameters (temperature, sliding velocity, applied load, atmosphere) on friction and wear of quasicrystal surface were studied. Microstructure of quasicrystal, morphology of worn surface, and wear debris were observed by scanning electron microscopy (SEM). The results showed that for QCs, the friction coefficient and roughness of worn surface were influenced by the parameters, especially greatly by the temperature. With rise of the applied load and sliding velocity, the friction coefficient decreased. The dominant wear mechanism at 350℃ was delamination for QCs. The cracks formed on the worn surface during the friction. Moreover, phase transformation was not observed on worn surface of QCs at 350℃. All the results are discussed and explained.
关键词:
Quasicrystal
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Z.M. Zhang
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C.J. Xu
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X.F. Guo
金属学报(英文版)
In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys, the flakes of rapidly solidified Mg-6.4Zn-1.1Y magnesium alloy with thickness of 50-60冚m were obtained by a melt spinning single-roller device, and then the flakes were processed into rods by reciprocating extrusion and direct extrusion. The microstructure of the alloy was analyzed by optical microscope and SEM, and the constituent phases were identified by XRD. Phase transformation and its onset temperature were determined by differential thermal analyzer (DTA). The analysis result shows that rapid solidification for Mg-6.4Zn-1.1Y alloy can inhibit the eutectic reactions, broaden the solid solubility of Zn in 冄-Mg solute solution, and impede the formation of Mg3Y2Zn3 and MgZn2 compounds, and thus help the icosahedral Mg3YZn6 quasicrystal formed directly from the melt. The microstructure of the flakes consists of the -Mg solid solution and icosahedral Mg3YZn6 quasicrystal. Dense rods can be made from the flakes by 2-pass reciprocating extrusion and direct extrusion. The interfaces between flakes in the rods can be welded and jointed perfectly. During the reciprocating extrusion and direct extrusion process, more Mg3YZn6 compounds are precipitated and distributed uniformly, whereas the rods possesses fine microstructures inherited from rapidly solidified flakes. The rods contain only two phases: 冄-magnesium solid solution as matrix and fine icosahedral Mg3YZn6 quasicrystal which disperses uniformly in the matrix.
关键词:
Magnesium alloy
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