Papers by Author: Pei Ying Liu

Abstract: 0.3%Er is added to Al-5.6Zn-1.9Mg-1.6Cu-1.0Li alloy (in wt.%) to investigate the effect of erbium on microstructure of the alloy. Most of erbium exists in the primary Al₃Er phases which are incoherent with the alloy matrix unevenly. A few of fine Al₃Er phases, precipitated from supersaturated solid solution, are coherent with the matrix. η′-MgZn₂ precipitates in the single-aged alloy are sparser than that in the double-aged alloy. A few of fine Al₃Er phases act as the heterogeneous sites of η phases. There exist some precipitation free zones in the matrix around fine Al₃Er precipitates. Erbium is segregated to grain boundary seriously. A few of Al₃Er phases are present in grain boundary. The grain boundary precipitates are not continuous about the Al₃Er phases.

Abstract: 1.1%Li was added to 7075 alloys to obtain the Li-containing Al-Zn-Mg-Cu alloys. The microstructure and hardness of the alloys are investigated by transmission electron microscopy (TEM) and Vickers hardness. The hardness of the single-aged alloys is low. When the alloys were double-aged or multi-aged, the hardness is comparable to that of Al-Zn-Mg-Cu alloys at peak ageing. Two peaks were present in the hardness curves of the multi-aged Li-containing Al-Zn-Mg-Cu alloys. With the last-step temperature increases, two-peak phenomenon becomes prominent. The density and size of precipitates are influenced remarkedly by the ageing processes. Coarse grain boundary precipitates and PFZ (precipitate free zone)can be observed when the Li-containing Al-Zn-Mg-Cu alloys were multi-aged, and the higher the last-step ageing temperature, the wider the PFZ is.

Abstract: The effect of ageing processes on the toughness and the yield strength of the Li-containing Al-Zn-Mg-Cu alloys (Al-5.6%Zn-1.9%Mg-1.6%Cu-1.1%Li-0.24Cr) was investigated. The microstructure was observed by transmission electron microscopy, tensile test was performed at a rate of 1mm·s-1, fracture toughness was experimentally determined by the impact test, and the fracture modes had been assessed by image analysis of scanning electron microscopy micrographs. The strength of the Li-containing Al-Zn-Mg-Cu alloys treated at 120 °C is not more than 430MPa, which is very lower than that of 7075 alloys. The strength is comparable to that of 7075–T6 alloys after double-ageing or multi-ageing, however its ductility is lower than that of 7075-T6 alloys. The single-aged Li-containing alloys have high toughness. The multi-aged alloys become brittle. The fracture surface for the Li-containing Al-Zn-Mg-Cu alloys is intergranular, since the intergranular precipitation weakness the grain boundaries.

Abstract: In the present work Mg-Li-X alloys with different alloying are investigated and the studies are focus on the stability of microstructures and properties of β base Mg-13Li-X alloys. The alloying elements concerned are aluminum, zinc, zirconium, rare earth. The microstructure and corresponding mechanical properties are examined with the aid of DSC analyses, X-ray diffraction and OM observation. The results showed that the hardening effect and the stability of the alloys varied with different addition of aluminum, zinc, zirconium, rare earth elements. The mechanical properties of the alloys greatly depend on the additional elements.

Abstract: The effects of Al, Zr additions on the microstructure and properties of a β matrix Mg-Li-Al-Zr alloy of hot forged, cold rolled and heat- treated states have been systematically investigated. The tensile properties of the alloy was tested, and microstructure was studied by X-ray diffraction and SEM methods. The results showed that the addition of zirconium in the aluminum containing Mg-Li alloy was effective for grain refinement. The alloy containing zirconium of rolled state exhibited higher strength and satisfied ductility compared with the alloy without zirconium. The existence of zirconium in the alloy was mainly in the form of Al-Zr compounds of Al2Zr andAl3Zr. The reason for less age-hardening effect may be caused by the capture of aluminum by zirconium and as a consequent by the lake of aluminum in the matrix.

Abstract: Metal ions were implanted into the surface of fiber with metal vapor vacuum arc source implanter. The resin matrix composite was made of the surface modified fibers. The microwave absorbing property of the composite was measured. It is shown that the microwave absorbing property of the composite was improved effectively by the ion implantation and the extreme reflectivity reached -6.13dB. The paper studied the microwave absorbing property of the composite material treated by ion impregnation and discussed mechanism.

Abstract: Ferromagnetic layer and dielectric layer of nanometer thickness were deposited alternatively on quartz glass plates to compose nanometer multiple-layers with microwave absorbing function by electrostatic self-assembly. The thickness of a double-layer composed of a ferromagnetic layer and a dielectric layer is 6~8 nm measured by UV-VS spectrophotometer. The nanometer multi-layer with total thickness of 100~200 nm exhibits obvious microwave-absorbing effect in the wave range of 8~18 GHz and the maximum attenuation reaches -16.85 dB. The wave-absorbing mechanism of nanometer multiple-layers was discussed based on the quantum theory

Abstract: In the present work the deformation behavior of magnesium alloys with different lithium content has been investigated in terms of microstructures, crystal parameters, textures and mechanical properties. The lattice constants of a phase (hcp) determined by XRD varied with its lithium content and at the same time there are some changes in the texture composition. The plasticity would remarkably increase while b phase (bcc) becomes dominant in the microstructure of alloys.

Abstract: The influence of Zn content and Zn/Mg ratio on the equilibrium phase amounts of major ageing strengthening phase η’ (MgZn2) in lithium containing 7000 series aluminum alloys has been investigated by means of thermodynamic calculations. The results show that, comparing with Li-free 7000 series aluminum alloys, Zn/Mg ratio is no longer the determinant for the amount of η’ and only increasing Zn content that can increase the amount of η’. And the results were discussed with existing experiments.