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mIcROSTRUcTURES AND PROPERTIES Of REcIPROcATINGLY ExTRUDED mg-6.4zn-1.1Y ALLOYS

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Acta metallurgica Sinica(English Letters) 2008年第1期21卷 37-42页

作者： z.m. zhang c.j. xu x.f. guo School of materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

An icosahedral mg3 Yzn6 quasicrystalline phase can be produced in mg-zn- Y system alloys when a proper amount of zn and Y is contained, and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy. In this article, phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast mg-6.4zn-1.1 Y alloy are analyzed. The microstructure of the as-cast mg-6.4zn-1.1 Y alloy consists of the α-mg solid solution, icosahedral mg3Yzn6 quasicrystal, and mg3 Y2zn3 and mgzn2 compounds. After the alloy was reciprocatingly extruded for four passes, grains were refined, mg3 Y2 zn3 and mgzn2 phases dissolved into the matrix, whereas, mg3 Yzn6 precipitated and distributed uniformly. The alloy possesses the best performance at this state; the tensile strength, yield strength, and elongation are 323.4 mPa, 258.2 mPa, and 19.7%, respectively. In comparison with that of the as-cast alloy, the tensile strength, yield strength, and elongation of the reciprocatingly extruded alloy increase by 258.3%, 397.5%, and 18 times, respectively. It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast mg-6.4zn-1.1 Y alloy, particularly for elongation. The high performance of the mg-6.4zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.

关键词： Reciprocating extrusion mg-zn- Y alloy Icosahedral quasicrystal

REcIPROcATING ExTRUSION Of IN SITU mg_2Si REINfORcED mg-Al BASED cOmPOSITE

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Acta metallurgica Sinica(English Letters) 2008年第3期21卷 169-177页

作者： z.m. zhang c.j. xu x.f. guo S.z. jia School of materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

m92Si reinforced mg-Al based composite with high amount o/silicon was prepared by permanent mould casting, and then extruded by reciprocating extrusion （RE） after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of m92Si and the mechanical properties of the com- posite were investigated, to develop new ways to refine the m928i phase and improve its shape. The result showed that RE was very useful in refining the m92Si phase. The more the RE processing passes, the better the refining effect would be. moreover, the uniform distribution of m928i phases would be more in the composite. After the composite was processed by RE for 12 passes, most m92Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. for the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 mPa, 211.4 mPa, and 3.3% at room temperature, whereas, 288.2 mPa, ,207.7 mPa, and 7.8%, respectively, at 150℃. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150℃. The m928i reinforced mg-Al based composite possesses good heat resistance at 150℃. The excellent resistance to effect of heat is attributed to the high melting tempera- ture and good thermal stability of fine mg2Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.

关键词： Reciprocating extrusion magnesium alloy In situ composite Elevated temperature property

mIcROSTRUcTURE Of BINARY mg-Al EUTEcTIc ALLOY WIRES PRODUcED BY THE OHNO cONTINUOUS cASTING PROcESS

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Acta metallurgica Sinica(English Letters) 2008年第4期21卷 275-281页

作者： z.m. zhang T. Lü c.j. xu x.f. guo School of materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

Directionally solidified binary mg-Al eutectic alloy wires of approximately 5 mm in diameter were produced by the Ohno continuous casting （Occ） process and the microstructure was examined. It was found that the wires possess obvious unidirectional growth characteristic along its axial direction. The microstructure consists of parallel columnar grains that resulted from the competitive growth of equiaxed grains solidified on the head of dummy bar. Each columnar grain comprises regular eutectic a-mg and β-mg17 Al12 phases, which grew along the axial direction of the wires. The morphology of the eutectic is mainly lamellar, meanwhile rod eutectic exists. The formation of rod eutectic was attributed to the ＂bridging effect＂ caused by incidental elements in the alloy.

关键词： mg-Al alloy Eutectic structure Directional solidification Occ process

EffEcT Of ANNEALING ON DAmPING cAPAcITIES Of AS-cAST zA27 ALLOY

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Acta metallurgica Sinica(English Letters) 2006年第5期19卷 379-384页

作者： z.m. zhang j. c. Wang H.z. Liu x.f. guo School of materials Science ＆ Engineering Xi＇an University of TechnologyXi＇an 710048 China State Key Laboratory of Solidification Processing Northwestern PolytechnicalUniversity Xi＇an 710072 China

zA27 alloy was prepared by casting with permanent mold and then annealed at 250℃ for 1-4h. The damping capaciG of the alloy was measured using a testing apparatus based on the cantilever beam technique. It was found that the as-cast zA27 alloy possesses high damping capacity with the value of 1.3 × 10^4 at 320Hz. After annealed at 250℃ for lh, the damping capacity decreases to 1.1 × 10^-3 and then remains constant even when the annealing time is increased to 4h. The microstructure of the as-cast zA27 alloy consists of large dendrites of Al-rich PrimaG （x-phases, eutectoid （α ＋ η） and nonequilibrium eutectic phases （α ＋ η ＋ ε）. After annealing at 250℃ for lh, the e phase disappears due to dissolution into the matrix, and the spacing between the flakes of eutectoid increases. The further increase in the annealing time has little effect on the spacing. The damping mechanism of the alloy was discussed considering the thermoelastic damping and defect damping. The value of thermoelastic damping accounts only for 7%-8% in the overall damping in cantilever beam damping measurements and the damping capacity of the zA27 alloy came mainly from defect damping.

关键词： damping capacity zA27 alloy annealing

EffEcTS Of ce ON cORROSION RESISTANcE Of Az91D mAGNESIUm ALLOY

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Acta metallurgica Sinica(English Letters) 2005年第2期18卷 129-136页

作者： z.H.Huang x.f.guo z.m.zhang c.j.xu SchoolofmaterialsScienceandEngineering Xi＇anUniversityofTechnologyXi＇an710048China

As-cast and corrosive microstructures of Az91D alloy containing various ce contents were observed by optical microscope (Om). The phase compositions of the alloys before and after the corrosion were analyzed by x-ray diffraction (xRD). meanwhile, the corrosion resistance of the alloys was tested by weight loss and potentiodynamic polarization curve methods respectively. The results show that rod-like Al4ce phase is formed in Az91D alloy containing certain ce content and as-cast microstructures are refined. Az91D-0.7%ce alloy has good grain refinement effect. The addition of ce can reduce the corrosion rate and corrosion current density of Az91D alloy and those of Az91D-0.1%ce alloy reach the minimum, which are 0.35mg/(cm2·d) and 2.761μA/cm2 with 75% and 86% reduction, respectively. The increasing volume fraction and reticular degree of β phase can improve the corrosion resistance of the alloys.

关键词： Az91D magnesium alloy ce modification microstructure corrosion resistance

GO/mgO/mg interface mediated strengthening and electromagnetic interference shielding in Az31 composite

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journal of magnesium and Alloys 2023年第10期11卷 3800-3814页

作者： z.Y.xu c.f.fang c.j.Li R.Wang x.P.zhang j.Tan Y.m.Wang Key Laboratory of Solidification control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian 116024China faculty of materials Science and Engineering Kunming University of Science and TechnologyKunming 650093China college of materials Science and Engineering Chongqing UniversityChongqing 400045China Key Laboratory of materials modification by Laser Ion and Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian 116023China

more requirements of electromagnetic interference(EmI) shielding performance are put forward for lightweight structural materials due to the development of aerospace and 5G communications. Herein, graphene oxide(GO) decorated with SnO_(2) coating is introduced as reinforcement into Az31 mg alloy. During the smelting process, the mgO layer is in situ gernerated at interface between GO and the molten mg alloy matrix by consuming SnO_(2). In the solid state, such kind of interface structure can improve the GO-mg interface bonding intensity,also significantly generate stacking faults. The Az31 composite reinfoced by trace modified GO(0.1 wt%) exhibits high ultimate strength and almost the same elongation with Az31 alloy. compared with Az31 alloy, the yield strength and ultimate tensile strength of composite are increased by 33.5% and 23.7%, respectively. meanwhile, the multi-level electromagnetic reflection from the multi-layer structure of GO and the interface polarization caused by the mgO mid-layer can significantly improve EmI shielding performance. The appropriate interface design strategy achieves the effect of “two birds with one stone”.

关键词： metal-matrix composites mechanical properties EmI shielding microstructures

Ion motion effects on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration

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High Power Laser Science and Engineering 2014年第2期2卷 1-7页

作者： W.P.Wang x.m.zhang x.f.Wang x.Y.zhao j.c.xu Y.H.Yu L.Q.Yi Y.Shi L.G.zhang T.j.xu c.Liu z.K.Pei B.f.Shen State Key Laboratory of High field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences

The effects of ion motion on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration are investigated by analytical modeling and particle-in-cell simulations. Studies show that the rear part of the transmitted pulse modulated by ion motion is sharper compared with the case of the electron shutter only. In this study, the ions further modulate the short-cycle pulses transmitted. A 3.9 fs laser pulse with an intensity of 1.33×1021W cm-2is generated by properly controlling the motions of the electron and ion in the simulations. The short-cycle laser pulse source proposed can be applied in the generation of single attosecond pulses and electron acceleration in a small bubble regime.

关键词： radiation pressure acceleration short-cycle pulses particle-in-cell simulations.

The characterization of fe-rich phases in a high-pressure die cast hypoeutectic aluminum-silicon alloy

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journal of materials Science & Technology 2020年第16期47卷 54-62页

作者： x.Y.jiao c.f.Liu z.P.guo G.D.Tong S.L.ma Y.Bi Y.f.zhang S.m.xiong School of materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced materials Processing Technology Tsinghua UniversityBeijing 100084China china fAW foundary co. LTDChangchun 130011China

Both microstructural characteristics and fracture behavior of fe-rich phases in a high-pressure die-cast hypoeutectic Al-Si alloy were *** was focused on the morphology and formation mechanism of fe-rich phases,together with their influence on *** show that primary ferich phases exhibited in blocky shape precipitated from liquid while secondary fe-rich phase in a large net shape was distributed along eutectic boundary participating in a ternary eutectic *** synchrotron x-ray tomography characterization,three fe-rich phases with different morphologies,i.e.,polyhedral shape,fine compact shape and chinese script-type shape were extracted along the radial *** slow-shot speed promoted the polyhedral fe-rich phase to precipitate in slow-shot sleeve while decreased the formation of fine compact and chinese script-type fe-rich phases in die *** of a worse deformation compatibility,polyhedral fe-rich phases fractured and became stress concentration sources before the failure of the casting.

关键词： Hypoeutectic Al-10Si fe-rich phases fracture morphology High pressure die casting

characterization of high-pressure die-cast hypereutectic Al-Si alloys based on microstructural distribution and fracture morphology

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journal of materials Science & Technology 2019年第6期35卷 1099-1107页

作者： x.Y. jiao j. Wang c.f. Liu z.P. guo G.D. Tong S.L. ma Y. Bi Y.f. zhang S.m. xiong School of materials Science and Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Automobile Safety and Energy Tsinghua University Beijing China china fAW foundry co. Ltd. Changchun 130011. China

The fracture behavior of high-pressure die-cast hypereutectic(HPDc) Al-Si alloys was investigated using a high-resolution laboratory cT and synchrotron x-ray tomography with a particular focus on the influence of HPDc microstructure. Results showed that microstructure of the alloy was mainly comprised of primary silicon particles(PSPs), Al dendrites, cu-rich phases and pores. most of the coarse PSPs, cu-rich phases and pores were located in the center of the specimen. The rapid solidification of HPDc led to a heterogeneous microstructural feature. Elemental cu was enriched in the frontiers of solid-liquid interface, causing the formation of large size dendritic arms. The pores were formed in the interdendrites which endured high stress intensity under high applied stress. microcracks were originated from pores and further connected cu-rich phases causing intergranular fracture. PSPs worked as obstacles causing piling-up dislocations in the phase interface. In the regions where large size of PSPs enriched in, PSPs ruptured rather than debonded from matrix, indicating transgranular fractures of PSPs. microcracks originated around pores and PSPs tended to converge on the main cracks to decrease the energy required for crack propagation.

关键词： Hypereutectic Al-Si alloy Primary silicon particles Porosity fracture morphology High pressure die casting