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Inhibition of Electromigration in Eutectic SnBi Solder Interconnect by Plastic Prestraining

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Journal of Materials Science & Technology 2011年第11期27卷 1072-1076页

作者： x.f. zhang H.Y. Liu J.D. Guo J.K. Shang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign. Urbana. IL 61801. USA

Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prestrain, Bi interfacial segregation to the anode, a clear indication of electromigration damage in SnBi solder inter- connect, was effectively prevented. Such an inhibiting effect is apparently contrary to the common notion that dislocations often act as fast diffusion paths. It is suggested that the dislocations introduced by plastic prestraining acted as sinks for vacancies in the early stage of the electromigration process, but as the vacancies accumulated at the dislocations, climb of those dislocations prompted recovery of the deformed samples under current stressing, greatly decreasing the density of dislocation and vacancy in the solder, leading to slower diffusion of Bi atoms.

关键词： Electromigration Interfacial segregation Prestrain Dislocation Vacancy

EffECTS Of DIffERENT fUNCTIONAL GROUP-CONTAINING ORGANICS ON MORPHOLOGY-CONTROLLED SYNTHESIS Of SILVER NANOPARTICLES AT ROOM TEMPERATURE

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 362-370页

作者： A.L. Wang H.B. Yin M. Ren x.N. Cheng Q.f. Zhou x.f. zhang faculty of Chemistry and Chemical Engineering Jiangsu University Zhenjiang 212013 China Department of Chemical Engineering Jiangsu Teachers University of Technology Changzhou 213001China

Silver nanoparticles with average particles sizes ranging from 2 to 131nm were manipulatively synthesized starting from silver nitrate using different functional group-containing organic modifiers at room temperature. The effects of the organic modifiers on the morphology of the resulting silver nanoparticles were strongly dependent on the intrinsic properties of the functional groups and the reducibility of the reductant. Numerous ether bonds （-0-）present in polyethylene glycol and Tween-80 were beneficial to the formation of silver nanoparticles with particle sizes of several nanometers in a narrow size distribution in both weak and strong reducing environments. Cetyltrimethylammonium bromide induced the formation of nanosized silver triangle plates in a weak reducing environment. The crystal growth of the silver nanoparticles with particle sizes of more than lOnm was postulated through an adhesion process of small-sized particles followed by a subsequent coalescence process under the present reaction conditions.

关键词： silver nanoparticle nanostructure crystal growth TEM (transmissionelectron microscopy)

MANUfACTURING Of ALUMINUM/fLY ASH COMPOSITE WITH LIQUID REACTIVE SINTERING TECHNOLOGY

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Acta Metallurgica Sinica(English Letters) 2002年第5期15卷 465-470页

作者： x.f. zhang, D.J. Wang and G. xieThe faculty of Material and Metallurgical Engineering, Kunming University of Science and Technology, Kunming 650093, China The faculty of Material and Metallurgical Engineering Kunming University of Science and Technology Kunming 650093 China

The Al/fly ash composites are fabricated by liquid reactive sintering P/M process with fly ash particles as intensifying phases. The reactivity and newly formed phases during liquid sintering process have been analyzed by combing Thermochemicdl data base calculation and xRD characterization. The results show that some of constituents in fly ash have reacted with liquid aluminum so that the elemental Si, fe, Ti as well as some amount of intermetallic compounds occur. The properties of aluminum/fly ash composites have been improved. With the fraction of fly ash increase, the composite density decreases; the hardness and the modulus of the composite increases, and the composite wear resistance are significantly increased. The fly ash reinforced composites represent a sort of low cost product with possible widespread applications in the automotive, small engine, and electromechanical machinery sectors.

关键词： aluminum/fly ash composite liquid reactive sintering

Identification and Measurement of Superabrasive Shapes

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Identification and Measurement of Superabrasive Shapes

MICROSTRUCTURES AND PROPERTIES Of RECIPROCATINGLY ExTRUDED Mg-6.4Zn-1.1Y ALLOYS

The International Conference on Surface finishing Technology and Surface Engineering

作者： D.W. Jia A.B. Yu x.f. zhang and Y. Chen Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University Tianjin China

＜正＞The measurement and identification method for superabrasive shape features was proposed based on digital image processing techniques. A system of shape measurement and identification was established in this paper. MATLAB software was programmed to fulfil the identification of grains. Image processing included digital image collection of abrasive grains by CCD, image enhancement, binarization, image filter and boundary detection. Equivalent shape was set to calculate the size of regular grains. As to irregular shape grains, the grains shape distribution could be determined with the shape coefficients. The results indicate that grain shape information can be detected by this measurement system. Grain size, size distribution and shape distribution can also be acquired. It is feasible and effective to apply digital image identification method to the identification and measurement of superabrasive shapes.

关键词： superabrasive image identification grain size shape.

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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

MICROSTRUCTURE Of Mg-6.4Zn-1.1Y ALLOY fABRICATED BY RAPID SOLIDIfICATION AND RECIPROCATING ExTRUSION

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Acta Metallurgica Sinica(English Letters) 2008年第1期21卷 30-36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

In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys, the flakes of rapidly solidified Mg-6.4Zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt spinning single-roller device, and the flakes were then 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 *** alloy can inhibit the eutectic reactions, broaden the solid solubility of Zn in α-Mg solute solution, and impede the formation of Mg3 Y2Zn3 and MgZn2 compounds, and thus help the icosahedral Mg3 YZn6 quasicrystal formed directly from the melt. The microstructure of the flakes consists of the α-Mg solid solution and icosahedral Mg3 YZn6 quasicrystal. Dense rods can be made from the flakes by two-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 Mg3 YZn6 compounds are precipitated and distributed uniformly, whereas the rods possess fine microstructures inherited from rapidly solidified flakes. The rods contain only two phases： α- magnesium solid solution as matrix and fine icosahedral Mg3 YZn6 quasicrystal which disperses uniformly in the matrix.

关键词： Magnesium alloy Rapid solidification Reciprocating extrusion Quasicrystal

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

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

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