Pei Ying Liu

Structure and properties of ultrafine-grained Al-Zn-Mg-Cu and Al-Cu-Mg-Mn alloys fabricated by ECA pressing combined with thermal treatment

Abstract An investigation was conducted on the structures and properties of aluminum-based alloys 7050 and 2224 with submicrocrystalline grains produced by severe plastic deformation through equal-channel angular pressing (ECA pressing). Special attention was paid to how the heat treatments before or after ECA pressing affected the structures and properties of alloys 7050 and 2224. The results showed that the ultimate tensile strength (UTS) of alloy 7050 reached 677 MPa, with elongation to failure of 15%, while the UTS of alloy 2224 reached 618 MPa, with elongation to failure of 12%. The forming of finer grains after ECA pressing resulted from cutting off shearing bands directly and from recrystallization at certain strain and annealing regimes. In this paper, three strengthening mechanisms were considered: grain refinement strengthening, high dislocation strengthening, and more homogenous and finer precipitations than the conventional T6-treated alloy.

Effects of Zr on Microstructures and Properties of a β Matrix Mg-13Li-3Al-0.7Zr Alloy

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.

Thermodynamics-Based Constituent Design of Lithium Containing 7000 Series Aluminum Alloys

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.

The Microstructures and Their Stability of β Base Mg-13Li-X Alloys

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.

Microstructure, Texture and Deformation Behavior of Lithium Containing Magnesium Alloys

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.

Improving the Microwave Absorbing Property of Fiber Reinforced/Resin by Surface Modification of Fiber through Ion Implantation

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.

Study of Microwave-Absorbing Property of Nanometer Multi-Layer

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