新型高强稀土镁合金的热处理工艺和强化机理研究

华中科技大学硕士学位论文新型高强稀土镁合金的热处理工艺和强化机理研究姓名：罗可申请学位级别：硕士专业：材料加工工程指导教师：张祥林;王爱华20080501IXRDTEMSEMEDSMg-5%Zn-1%Y-0.6%Zr-0.8%Ce/NdMg-15%Gd-3%Y---/Mg-5%Zn-1%Y-0.6%Zr-0.8%Ce/NdMgZn2Mg-Y-Zn-ZrMg-15%Gd-3%Y5(,)MgGdY3MgGd245MgY''β'β3MgGd'''19()()()SSSSDOcbcofccβββ→→→''β'ββ''β'ββ;;;;IIAbstractEffectsofaddedrareearth(RE)elementsandheattreatmentparametersonmicrostructureandmechanicalpropertiesofMg-5%Zn-1%Y-0.6%Zr-0.8%Ce/NdandMg-15%Gd-3%Yalloyswereinvestigatedinthisdissertation.Themicrohardnessandtensiletestcombinedwithscanningtransmissionmicroscope(SEM)incorporatingenergydispersivespectrum,X-raydiffractionanalysis(XRD),highresolutionelectronmicroscope(HREM),revealedtherelationshipamongstchemicalcomposition–microstructure–deformationbehavior–mechanicalproperties.Ithasbeenpointedoutthattherefinementofmagnesiumalloybyaddingrareearthwascausedbyhighundercoolingdegreebetweenthesolid/liquidinterfaceduringsolidificationandhighnucleationrate.Anoticeablegrainrefinementbyaddingminorrareearthinthemagnesiumalloyswasobserved.Itconcludedthat,forMg-5%Zn-1%Y-0.6%Zr-0.8%Ce/Ndsystem,grainrefinementandageingstrengtheningarethemainstrengtheningmechanisms.BesidesthecertainstrengtheningMgZn2phaseinit,thequasi-crystalMg-Y-Zn-Zrisalsoapossiblestrengtheningphase.ForMg-15%Gd-3%Ysystem,besidestheageingprecipitationasthemainstrengtheningmechanism,work-hardening,dynamicrecrystallizationandtwinninghavealsomadecontributiontodeformationandmechanicalproperties.Thestrengtheningprecipitatesinthealloyaremeta-stablephaseof5(,)MgGdY3MgGd245MgY.3MgGdexistinginthealloyisapossiblestrengtheningphase.Theprecipitationsequenceofthissystemis:'''19()()()SSSSDOcbcofccβββ→→→.Theprecipitationphasesatpeakagingstatemainlyconsistsofmetastablephase'β.Byanalyzingmechanicalpropertiescombinedwithcharacteristicofprecipitatesfordifferentageingperiods,it’sconcludedthat''βand'βarebetterprecipitatesthanβforthisalloy.Keywords:Rareearth;Precipitationstrengthening;Ageing;Meta-stablephase;Mechanicalproperties200_____200200111.11.1.11224.30502.5%8648.81107201.74g/cm3[1-15][16][17-21]1.74103kg/m3(1.31.9)103kg/m3Mg-Li0.95103kg/m330%50%70%2951.1.2150kg3820033[22-33]1-11.1.31.21.2.1[24]4[34]-MgSSSS→()GP→()''β→'ββ→GP1.2.25HCPHall-Petchσs=σ0+Kd-1/2Hall-PetchK300~320MPa(um)1/24ECAEECAE1-21-2ECAEECAE6ZK6040~80mµECAE1.6mµ[35]1.2.3(581012)1993Mg-Zn-YMg3Zn6Y20(IQC)M-Zn-REMg-Zn-REMg-Zn-YMg3Zn6Y-Mg180MPa~480MPa[36-37]Mg-Zn-YMg-Zn–REREYGd~Er20Hume-RotheryMg-Zn-YMg-Zn-YMg-Zn-YMg-Zn-YIMg3Zn6YG.YuanMg-Zn-YSighn.AMg-Zn-Y[38]1.2.47SiCA12O3SiCA12O3SiCMg2Si1.31.3.124f014s5d4f324OS[39][40-41]8300Mg-NdMg-YMg-Gd1.3.1.1Mg-NdNdNd3.6wt0.63at%Mg-Nd[42-43]Mg-NdG.P’’’G.P180G.PMg[0001]G.P[42]Mg{1010}G.P[43]200260D019Mga=2aMgc=cPikeNoble[42]a=0.52nmc=1.3nmKarimzadeh[43]a=0.735nmMg2Nd17a=1.031nmc=0.593nmMg12NdMg-Gd-NdMg-Gd-Nd1.3.1.2Mg-YY12%Y9YMg-RE10%Y260(Mg-Y)9%Y1%ZnYTh370CThYMg-LiYMgMg-YMg-YWE54(Mg-5.1%Y-3.3%RE(Nd)-0.5%Zr)WE43(Mg4.0%Y-3.3%RE(Nd)-0.5%Zr)1.3.1.3Mg-GdMgGdMg-Gd:ScMnYZrGdDritsMg-9.3%Gd-4.8%Y-0.6%Mn[44]450MPa3500C160MPa(350)MordikeMg-GdScMnMg5%Gd-1%Mn-0.3%Sc30040MPaWE54[45]GdDyMg-6%GdDy-3%Nd-ZrWE541.3.1.4EK-QE22QH21EQ21QEEZ33EQ21250QE22A10[46-47]2080--2090WEWE54WE54RR3501989MELWE43McDonnellMD500[48]MC8(EZ33A)MC9(QE22A)MC10(ZE41A)[49]2090[50-51]2070Mg-Y-Zn-Zr809630ZM31967200M71.51980ZM6ZM6250ZM6M10ZH62A[52]2080[53]111.3.23090%5%.1-3121-3[54]{0001}{1012}[55]138%;25%;8%Starselsky.AAZ31B[54]1.41.4.1GP11%(CaZn)141.4.2NdCeZKMg-Gd1YCeNdZKGd2Mg-Zn-Y-Zr-REMg-Gd3(TEM)(SEM)(EDS)XXRD4Mg-Zn-Y-Zr-RE230Mpa16%Mg-Gd456Mpa10%Mg-Zn-Y-Zr-RE280Mpa16%Mg-Gd480Mpa10%1522.12-12-12.2ZKMg-Zn-Zr7075ZKGPMg-ZnZrNdCeWEMg-Y-GdGd10%16ZKWEMg-5%Zn-1%Y-0.6%Zr-0.8%Ce/NdMg-15%Gd-3%YNdCeGd2.32.3.1HV-BuchlerIII(HV)50N2052.3.2CSS-441001mm/min2.3.3XXD-MAX-3BX40KV30mA;JADE5.0PDF20042.3.4SEMEDSSEMEDSEDAXJSM-5610LV2.3.5MatlabMATLABSEMMATLAB17SEM200SEMMATLABimcropbwlabelnnMatlabi=imread('');%g=rgb2gray(i);%figure,imshow(g);%title('');im=imadjust(g,[0.5,1],[],1.4);%m=medfilt2(im);%figure,image(m);%title('');bw=im2bw(m);%figure,image(bw);%bw1=bwmorph(~bw,'thin',inf);%bw2=~bw1;%bw3=imcrop(bw2,[50100400300]);%[l,n]=bwlabel(bw3,4)%n2-2182-22.3.6JEM210030umF3mmGatan691PIPS193Mg-5%Zn-1%Y-0.6%Zr-0.8%Ce/Nd3.13.1.1Mg-5%Zn-1%Y-0.6%Zr-0.8%Ce/Nd99.9%Mg-20ZrMg-50CeMg-50NdZr780500MgCl27602015cm12cm2cm3-1X3-1Mg-5%Zn-1%Y-0.6%Zr-0.8%Ce/Nd203.1.2Mg-5%Zn-1%Y-0.6%Zr-0.8%Ce/Nd335039043035h15h24h10%NaCl20011.522.533.54%2~33.2NdCe3-2SEM35~60umCeNdZrCeNd350~430243-2200SEM:(a)+Ce;(b)(+Nd)CeNd3-3(a)(b)21CeNdMg12NdMg12Ce3-43-33-412MgNd:(a)[2110]BF;(b)[2110]SAED[2110](a)(b)20um20um22Mg12NdMg12Ce/CeNdK1/∆T=TL-TS3.33.3.13-5XXZrMgZn2Mg-Y-Zn-Zr400460Mg-ZnMgZnMgZn2,J.B.ClarkD.Y.MaengMg-ZnMgZn2MgZn2D.Y.MaengMgZn2,a=0.515nm,c=0.850nm,MgZn,,,2320304050607080bbb246015hcdaddcccbbbaaaaaaadcba3905hMg3Y2Zn3MgZn2Mg-Y-Zn-Zrα-Mg3-5XRD+Nd3-63-7Nd1Ce2MgZn2Mg-Y-Zn-ZrMgZn2Mg-Y-Zn-Zr243-6MgZn2:(a)011BF;(b)011SAED3-7MgYZnZr−−−:(a)1213BF;(b)1213SAED3.3.2135039043046051546024(b)(a)(b)(a)(200)(000)()211(011)()0111()1101()0000()101025(1)(2)(15h)(5h)10MPa(3)39015h(4)15h1+Ce(HV)(+Nd)(HV)350+5h112.6