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INVESTIGATION OF PHYSICO METALLuRGICAL PHENOMENA FOR THE CC FORMING OF WCP/Fe C COMPOSITES

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Acta Metallurgica Sinica(English Letters) 1999年第4期12卷 566-572页

作者： B.Z. Li1) ,Y.P. Song1) ,k.u. kainer2) , H. Zhang3) , J.P.Xie1) and R.Xiang4) 1) Department of Materials Engineering ,Luoyang Institute of Technology ,Luoyang 471039 ,China2) Institute of Material Science and Technology ,Tu Clausthal,D 38678 Clausthal

Theinvestigation of physicometallurgicalphenomena forthe CC formingof WCP/ Fe Ccom posites wasperformed. Resultsshow that underthe patentcondition, WCP/ Fe Ccomposite surfacelayerof16 20 m m heavycross sectioncan beacquiredintheoutsideofa hollow cylin der. The surface of CTC particlescould be partially dissolved by Fe containing melt. Thefineshortstick like WCcrystallitesarein situseparated neartothesurfaceof CTC *** from the CTC particles,someseparated, finetungsten carbidecrystallitesand Fe, W,Mo and Cretc. containing web composite carbides, are distributed on the matrix of WCP/ Fe Ccomposite. Fe Calloy matrix of the hollow composite cylinder is alloyed in differenthigh levels.

关键词： physicometallurgical phenomena CC forming WCP/ Fe Ccomposites of heavycross section

Microstructure evolution and tensile properties of friction-stir-welded AM50 magnesium alloy

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中国有色金属学会会刊：英文版 2008年第A01期18卷 76-80页

作者：曾荣昌 W.DIETZEL R.ZETTLER 陈君 k.u.kainer School of Materials Science and Engineering Chongqing Institute of Technology GkSS-Forschungszentrum Geesthacht GmbH Geesthacht 21502Germany

Friction stir welding(FSW) technique was utilized to weld cast AM50 magnesium alloy *** microstructures in the base metal(BM) and the weld joint were observed by optical *** mechanical properties were investigated by using hardness measurement and tensile test,and the fractographs were observed by scanning electron *** results show that the microstructure of the base material was characterized by bulk primaryαphase,α-matrix and intermetallic compoundβ(or Mg_(17)Al_(12)),and the weld nugget exhibiting recrystallized microstructure consists ofα-matrix andβ*** grain size in the weld is smaller than that in the base *** hardness of the weld joint is improved but the tensile strength and yield strength,as well as the elongation to failure of the base material *** fracture of BM has a rougher surface with more dimples,which is a characteristic of the ductile fracture,whereas the fracture on the nugget reveals a quasi-cleavage *** ultimate tensile strength and yield strength of the FSWed AM50 are 86.2%and 94.0%of those of the base metal,respectively.

关键词：镁合金焊接法搅拌摩擦焊微观结构

Review of studies on corrosion of magnesium alloys

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中国有色金属学会会刊：英文版 2006年第B02期16卷 763-771页

作者：曾荣昌张津黄伟九 W.DIETZEL k.u.kainer C.BLAWERT 柯伟 School of Material Science and Engineering Chongqing Institute of Technology Chongqing 400050China School of Material Science and Engineering Chongqing Institute of Technology Chongqing 400050 China GkSS-Forschungszentrum Geesthacht GmbH Geesthacht 21502 Germany Environment Corrosion CenterInstitute of Metals Research Shenyang 110016China

This review provided some recent progress of the research on corrosion mechanisms of magnesium and its alloys and a basis for follow-on research. Galvanic corrosion, pitting corrosion, intergranular corrosion (IGC), filiform corrosion, crevice corrosion, stress corrosion cracking (SCC), and corrosion fatigue (CF) were discussed. The influence of metallurgical factors such as alloying elements, microstructure and secondary phases, processing factors such as heat treatment and weld, and environmental factors including temperature, relative humidity, solution pH values and concentration on corrosion were discussed. In particular, a mechanism of pitting corrosion caused by AlMn particles was proposed. The corrosion properties of AZ91D weld material were investigated.

关键词：镁合金腐蚀疲劳相对湿度研究综述

Magnesium stress corrosion cracking

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中国有色金属学会会刊：英文版 2007年第A01期17卷 150-155页

作者： N. Winzer A. Atrens W. Dietze G. Song k. u. kainer Materials Engineering The University of Queensland Brisbane Australia Swiss Federal Laboratories for Materials Science and Technology EMPA Dept 136 lSrberlandstrasse 129 CH-8600 Dubendorf Switzerland GkSS-Forschungszentrum Geesthacht GmbH Germany

The significant positive green environment influence of magnesium alloy usage in transport could be compromised by catastrophic fast fracture caused by stress corrosion cracking(SCC). Transgranular stress corrosion cracking(TGSCC) of AZ91 was evaluated using the linearly increasing stress test(LIST) and the constant extension rate test(CERT). The TGSCC threshold stress was 55-75 MPa in distilled water and in 5 g/L NaCl. The TGSCC velocity was 7×10-10-5×10-9 m/s. A delayed hydride-cracking(DHC) model for TGSCC was implemented using a finite element script in MATLAB and the model predictions were compared with experiment. A key outcome is that,during steady state TGSCC propagation,a high dynamic hydrogen concentration is expected to build up behind the crack tip. A number of recommendations are given for preventing SCC of Mg alloys in service. One of the most important recommendations might be that the total stress in service(i.e. the stress from the service loading + the fabrication stress + the residual stress) should be below a threshold level,which,in the absence of other data,could be(conservatively) estimated to be about 50% of the tensile yield strength.

关键词：压力抗腐蚀强度氢化合物合金

Microstructure and corrosion behavior of Mg-Sn-Ca alloys after extrusion

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中国有色金属学会会刊：英文版 2009年第1期19卷 40-44页

作者： T. ABu LEIL N. HORT W. DIETZEL C. BLAW ERT Y. HuANG k. u. kainer k. P. RAO GkSS Forschungszentrum Geesthacht GmbH Max-Planck Strasse 1 Geesthacht 21502 Germany City university of Hong kong 83 Tat Chee Avenue Kowloon Hong Kong

Mg-Sn-Ca alloys promise a reasonable corrosion resistance in combination with good creep resistance, likely due to the presence of Ca2-xMgxSn and other phases. The selected alloys with 3% Sn and Ca in the range of 1%-2% have been extruded in order to achieve more homogeneous microstructure compared with the as-cast alloys. Optical microscopy(OM) and X-ray diffraction(XRD) techniques were used to study the microstructure and phases of these alloys. The corrosion behavior of these alloys was investigated by means of salt spray test and potentio-dynamic measurements. The results obtained on the alloys Mg-3Sn (T3), Mg-3Sn-1Ca (TX31), and Mg-3Sn-2Ca (TX32) indicate the presence of the same phases in as-cast and after extrusion, namely Mg2Sn, Ca2-xMgxSn, and Ca2-xMgxSn/Mg2Ca, respectively. However, due to the occurrence of extensive recrystallization in the extrusion process, the grain size has significantly reduced after extrusion. The reduction leads to the improvement of the corrosion resistance after extrusion which is then comparable with the commercial alloy AZ91D.

关键词： Mg-Sn-Ca合金腐蚀镁合金金属腐蚀

Electrochemical behavior of magnesium alloys in simulated body fluids

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中国有色金属学会会刊：英文版 2007年第A01期17卷 166-170页

作者：曾荣昌陈君 W.Dietzel N.Hort k.u.kainer School of Materials Science and Engineering Chongqing Institute of Technology GkSS Research Centre Geesthacht CmbH Geesthacht 21502Germany

Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids(SBFs). The influence of materials,solutions and their temperature on corrosion rate was mainly discussed. The results demonstrate that the free corrosion potential(Ecorr) of AZ31 and AZ91 alloys rises rapidly at initial stage,and then stabilizes at some value. Ecorr of WE43 alloy increases continuously. While Ecorr of AZ91 alloy with macro-arc oxidation(MAO) coating decreases drastically in 3 min,and then fluctuates between -1 607 mV and -1 503 mV. The WE43 alloy has better corrosion resistance in Hank's solution,compared with AZ31 and AZ91 alloys. Corrosion rates of the alloys are sensitive to the chemical composition and temperature of SBFs. A thin MgF2 film slightly improves corrosion resistance. An MAO coating on AZ91 alloy significantly reduces corrosion rate and enhances Ecorr. Pitting corrosion occurs on both AZ31 and WE43 alloys in Hank's solution.

关键词：镁合金生物材料腐蚀特性氧化技术

Corrosion behavior of Mg-Gd-Zn based alloys in aqueous NaCl solution

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Journal of Magnesium and Alloys 2014年第3期2卷 245-256页

作者： A.Srinivasan C.Blawert Y.Huang C.L.Mendis k.u.kainer N.Hort Helmholtz-Zentrum GeesthachtInstitute of Materials ResearchMax-Planck-Str.121502 GeesthachtGermany CSIR-National Institute for Interdisciplinary Science and Technology Pappanamcode(P.O)Thiruvananthapuram 695019India

The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was *** of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)*** morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in *** dendrites were finer in size and highly branched in *** corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn ***-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the *** micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second *** stability of the second phase at the grain boundary was altered and dissolved after the long immersion *** the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.

关键词： Mg-Gd-Zn alloys Micro-galvanic corrosion Polarization Electrochemical characterization

Microstructure and mechanical properties of as-cast Mg-Sn-Ca alloys and effect of alloying elements

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Transactions of Nonferrous Metals Society of China 2013年第12期23卷 3604-3610页

作者： k.SuRESH k.P.RAO Y.V.R.k.PRASAD N.HORT k.u.kainer Department of Mechanical and Biomedical Engineering City University of Hong Kong Consultant *** No. 2/B Vinayaka Nagar Helmholtz-Zentrum Geesthacht Institute of Materials Research Magnesium Innovation Centre

The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg-Sn-Ca （TX） alloys was studied in the temperature range of 25-250 °C and correlated with the microstructure. The Sn to Ca mass ratio up to 2.5 contributes to the formation of Mg2Ca phase at the grain boundaries and CaMgSn in the matrix, while a ratio of 3 gives only CaMgSn phase mostly in the matrix. While the compressive strength decreases with the increase in temperature, for Sn/Ca up to 2.5, a plateau occurs in 100-175 °C, which is attributed to the strengthening by Mg2Ca. However, for ratio of 3, the strength is lower and decreases more gradually. Mg-3Sn-2Ca （TX32） has the highest strength and the addition of 0.4%Al increases its strength but simultaneous addition of Si lowers the strength. Likewise, the addition of Zn improves its strength but simultaneous addition of Al slightly decreases the strength. The results are correlated with the types of intermetallic phases that form in various alloys.

关键词： Sn/Ca ratio Mg-Sn-Ca alloys alloying additions microstructure compressive strength

Bulk and local textures of pure magnesium processed by rotary swaging

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Journal of Magnesium and Alloys 2013年第4期1卷 341-345页

作者： W.M.Gan Y.D.Huang R.Wang Z.Y.Zhong N.Hort k.u.kainer N.Schell H.-G.Brokmeier A.Schreyer Institute of Materials Research Helmhlotz-Zentrum GeesthachtMax-Planck-Str.1D-21502 GeesthachtGermany Institute for Materials Science and Engineering Clausthal University of TechnologyAgricolastrasse 6D-38678 Clausthal-ZellerfeldGermany

Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.

关键词： Rotary swaging Pure magnesium Bulk and local textures