The plane strain deformation of model continuous fibre composites such as Cu-W provides a vehicle for the study of the macroscopic effects of second phase particles on the strain distribution in the matrix and its possible effects on subsequent recrystallization behaviour. By using metallographic studies based both on optical gridding methods and low temperature recrystallization, the pattern of flow enforced by the fibres can be quantified and related to the spatial distribution of recrystallization events

Embury, J.D. (McMaster Univ., Hamilton, ON (Canada))

Kocks, U.F. (Los Alamos National Lab., NM (United States))

Poole, W.J.

Silvetti, S.P. (Cordoba Univ. Nacional (Argentina))

UNT Digital Library

m92 011364TITLE ON RECRYSTALLIZATIONIN METALMATRIXCOMPOSITESAUTHOR(S) U. J. PooleS. P. SIlvettiJ. D. EmburyU. F. Kock9SUBMITTEO TO Inter. Conf. “Recrystallization 92”’San Sebastian, Spain, August 31 -September 4, 1992D1.S(”LAIMERi’,Thim rcfmrl wm fvrcpmrrxl un an ntwtrum t~f work sfwmMmdhy mvqcrrcy of Ihe llmwd SImwe(kernmcrrl Ncllhcr Ihc llnltd Slnlcn(k]vcrnmcnl rrorarvy ngerrcy thcronf, nor nnyof Ihawemployees. mtihem unv wnrrnrrly, cxfrrcm or m@w4f, or nmumch ●vy lc~al lIshdIly or rcsfnmuhdlty for the uccurwy, Lwmplclerrem. w usc(ulnewo[ Mrw mformhlmn, nppmrmus, prmfuc:,orprmxm di=lmml. nr rcprcxrrls !hal IIS use wmIld nol mfrmSc Fwnlcly OWM rlghln Mcfcr-crruc hcrcm 10 any ~~lflc wrrvmcruud produot, frrucem, w wrvicc hy irnde name, lrrndcmarh,mmvulncturcr, or nthcrwmc d~x~ not ncunnardy crmIIItuIc or Imply II* cndnrwrmm, rcwn-mcmfalmn, or favormm hy Ihc [Imkd SIaIcs fiovcrmnem or iny ●gency Iherwof I“hc vrcwnwrd upmmrvn or rnulhors cmprcmm! hrrcln do nor rruusnrlly male m rcflcd Ihmc of Ihe1Imlcd SIaICI ( iovcrrrmcm or any ●mcrruy Ihcru,flhDSNf31DTl10S LosAlamos,NewMexico87545Los Alamos National LaboratoryI,,nw)#@Bum, MU-H ~.!*,.,...!On Recrystallization in Hetal Matrix CompositesU.J. Poolel, S.P, Silvettiz J.D. Emburyl and U.F. Kocks3,1) 14cMaster University, Hamilton, Ont., Canada2) Universidad Naticmal de Cordoba, Argentina3) Los Alamos National bboratory, Los .41SMOS, NH 87545, USAKey Words: Metal Matrix Composites, Copper, Recrystallization.ABSTRACTTho plane strain deformationof model continuous fibra composites such ●a CU.Wprovidos ● vohiclo for tho study of the macroscopic ●ffocts of second phaseparticlao on the strain distribution in tho matrix ●nd its possiblfi ●ffaces onsuhaquont recrystallization behaviour. By using metallograpnic studios based bothon optical aridding methods ●nd low tomporature recrystallization, tha pactorn offlow ●nforced by tho fibros can be quantified ●nd rolatod to the ●patlaldi~tribution of racrymtallization ●vonta,INTRODUCTIONme ●ffects of sacond phaao particles, of order 1=S pm, on deformation ●ndwbsequont recrystallization have boon ●x~inod by ● numbar of authors, particularlyin the seminal work of Humphroys ●nd co-workers [1]. Theo cffacts ●re conccrnodlarg~ly with tho nature ●nd ●xtont of local ntrain #radionta that occur around hardsecond phasa psrticlas ●nd tho local dislocation structures which ~ivo rias toparticlo ●timulatod nucleation. Howevor, in composite matarialo con~aining ●itherpmticulatea or fibres which ●re in ganaral #rester in scale than t}e gra.’n ●izc ofthe polycryatalline matrix, ● second ●ffmct can occur due to the influenca of thepartlclea on the macroscopic flow pattern of tho matrix during deformation ●nd thelnfluonco of this flow pattern on tho spatial di~tribution of ●ubaequentroc~stalllzation ●vents.It is this l?ttor ●spect of deformation which hae bocn considorsd in thrproeant work by using ● modol ●yatcm of l,Orn Uwiros ●mbedded in ● polycryctallin~Cu matrix with ●n ●vorago grain size of 100 ~m, Tho ●xporimonts psrfonsed on this●ystcm provid, a comprohcnsivo ovorview of the macroscopic deformation of cornposit~s● t lar~e plastic strains because they permit comparison with ~init~ ~lcm?nt method(FCM) calculations of well characterized impos~d flow proc~su.s ●nd th~datormination of tho spatial distribution of taxture both in tho deformed •n~rocryatallizcd conditions.EXPERIMENTALThe composites were fabricated from 1 mn diameter corumercial quality ●s-drawntungsten wire ●nd 99.99 Q copper. The compoeite was prepared by liquid metalinfiltratlo~ under vacuum in ● ●edified crystal growing furnace, The tungstenfibros were held Inplaca during the castingby graphite spacers. The distributionof fibres, the sample dimensions ●nd orientation of deformation axe~ ●re shown inFig. 1. In order to refine the ● s-cast stmcture in tho copper matrix, thecomposite was deformed in channel die compression with the fibros perpendicular tothe- die walls. Thie ●nablod thedeformation to be imponod in ●controlled ●arine r ●nd reducad thepossibility of void formation at thefibro.matrix interfacm. The compomitewas deformed 15 9 ●nd then rotated 90de~raes ●round the fibre axis anddeformed ● similar eaount. Thinreturned the aemplo to ●pproximately itsoriginal dimensions. Iho samples werethen ●nsalsd for 30 ●inutee at 500 ‘C.This deformation procedure wcs thenrepeated and tha samples ●naaled ● t 400‘C for 30 minutss to further refine thegrain structurs, The rasulting ~rainsize was 50-200 P (see Fig. 2) so thatghero were on ●verage 5-10 grainsbemaen fibras. The samples wero then-tallographically proparod and ● fine@d was place on tha ●~le face~rpmdicular to cho fibros by the-thod due to Attwood and Uuzledine[2] . The raeultin~ grid spacing wae 23~ and la shown in ?1s. 3a.After measuring the lnitiel grainClitu, tho compositor vero deformed in ●channel die. Teflon tape with Molykotelubrlcai~t sprayed on the side of thewpe ●djacent to the sample waa used to■inimizo tho ●ffects of friction bawaenthe ●emple and die wane. As ● resultof the lubrication practicoa, it watobsomed that the samples deformed in ●macruscopically homogeneous nmwter withthe free faces mmeining plane. Thesamples wers defermed in 15 Q lncrownteto ● total defamation of 309. Thetaflon lubricant was ~oplacod bo~oenstrain Incromenta, The sample wae thensectioned for metellographic preparation●nd varioue sections ●nnealed fordiffarent tiws ● t 300 ‘C, Thentallographlc preparation includedgrlndin~ up to 4000 grit and li%htTwoaLm Flbros, 1 ~ dlsND14 m J-R.D,1,0,?iguro 3. Schematic of sampleSiquro 8. Initial mi:.rostructursdiamond (6 ●nd 3 pm) and ●lwina (0,3 ~) pollshen to reduce ●urfacr rellcf ●ff~ctsbetween the tungotan ●nd copper, me matrix war ●tched in ●n ~onium porsulphatcsolution (10 s -Inlum pereulphate , 100 ●l distilled HaO) for up to 6 mlnutos,.:,tFlqure 3. Back scattar.d .loctron imsge ef ●) initial gridb) doformd grid (30 %)USULTS AND DISCUSSIONSpocimaru woro gridded ●nd comprossad 30t in channel die compression Theform of tha ●rface &rida befora ●nd ●fc.r d.ofomation 18 shown in Fi~. 3, l%e8trains wcro rnasurad by coruidorlng tho location of cha corners of the ~rids andth changes in location with deformation [3,4]. Errors ●riso both dut to the finitewidth of tha grids and tho ●ssumption that no displacamonts occur porpondicultr totht plant of tha grid, Tha ~asursd VonHisos ●quivalcnt strain distribution isillustrated in Fit. 4, A finito .Icmcntrnthod simulation baaad on AMQUS w68us.d to calculate tha distribution ofVon Hisas strass ●nd 8tr4in forcomparison with tha cxporimontal data.By Inputing ●n initial flow stress oftha copp~r ●nd tun~st~n, 20MPa ●nd 3000Mra racpactivoly, and a pioco.wi$olinear plastic flow curio for tha copporbated on pur. “>ppcr ●xparimontal data,tho Von HIBOS stress find retraindintributionm ohovn in Fi~, 5 ar.obtainod, Tho comparison with the●xparimsntal data in Fig, 4 is va~ Igood ?i~ro 4.FollovlnsExporimontal Von ?l~sesdeformation,recrystallization atudias woro carriedstrain d~stribut~onout ●t 300 ‘C for various periods ofti~~ in ordor to aso.ss tho spatial distribution of th. racrysta]]iza[ion c~’cr):sIn discussing tho rocrystallizttion ~oquonc., con~ld~ratlon W*S ~lvon CO the rc]r~iguro 5. FEM results for 30~ deformation a)b)of initial grain size on recrystallization. The previous[5] ●nd Hutchinson [6] indicates that in fine grainedb)Von Mises StrainVonRfises S~ress (MPa\work of Clarebrough et al.materials the process ofrecrystallization is ●ccelerated. Thus , a saries of metallographic observationswore undertaken to ●scertain that the influence of variations $n grain size in theinitial undeformed sample was much less than tha ●ffects of the strain distribution●nforced by the tungsten flbres,After ●nnealing for 30 minutes ● t 300 ‘C, the pattern of racrystalllzation isshown in Fig. 6a, It canbe seen that there ●re many ●mall, ●qulaxed grsins in theregions of highest Von 14ises strain between the particles: we take these to berecrystallized, Under the particular geometry used these produce bands between theparticles perpendicular to the compression direction. A more detailed ●xaminationof the distribution of recrystallization ●vents shown in Fig. 6b shows thatrecrystallization ●lso starts ● t the ●dge of the small zone of constraineddeformation close to the particles, It is interesting to note that the zones ofhigh shear strain ●nd large rigid body rotations on the diagonal between the fibre~●re less ●ffective initiating recrystallizatation ●vents,In rationalizing the experimental observations it is useful to consider thatthe recrystallization process must depend both on the ●ccumulation of stor?d energy●nd of local lattice mis?rientations necesscry to initiate recrystallization, Acruda ●pproximation for the distribution of stored energy can be made by consideringthat the total ●tored anorgy due to dislocations 1s proportional to the square ofthe flow stress. Thus, contours of the square of the Von Mises stress can beplotted ●s shown in Fig, 7 ●nd compared with the distribution of initialrecrystallization ●vents (Fig, 6a),This comparison indicates ●n important difference between the macroscopiccomposites considered in tho current work ●nd the ●ffects of 1 pm sizs particlesinvolved inpartlcle stimulated nucleation, Recrystallization does not occur ● t thelarge macroscopic particles but occurs in the region of amplified Von tliscs strainwhich occurs ●s ● i~onsequenca of ~~ of & imposed by the particles [7]It should ●lso be noted that tho recrystallization is ●cc~lerated in specific areasof the fl~w pattern, f,m. in regions of maximum Von llises strain,●)b)?iguro 6. R.crystallization patt@rn after ann.sling @ 300 ‘C for 30min. a) low magnification b) high magnificationCONCLUSIONSThe present work Indicat<s the value of model systems for the study of straindistributions and the subsequent spatial distribution of recrystallization etientsin metal matrix composites. The method outlined allows the pattern of flow to berelated to the spatial variation of texture ●nd recrystallization. The studiesindicate the importance not only of Local #train gradients at particles but of thedirect influence of large particles on the pattern of deformation ●nd the spatialvariation of stored energy on recrystallization in metal matrix composites.1ACKNOWLEDGEMENTSThe ●uthors ●re grateful to the U.S.Department of Energy, the NaturalSciences ●nd Engineering ResearchCouncil (Canada) ●nd the Ontario Centrefor !4aterials Science for researchsupport. They are particularly gratefulto Dr. S. MacEwen (Alcan InternationalLtd.) for the FEM computations ●nd toProfessor P.R. DawsonUniversity) and Professor R, Sowerby(14ctlaster University) for discussionsconcerning the ●nalysis of large straindeformation,?~guro 7. The 8quare of the VonHisas Stress (relative units)assumed to b. proportional tostor.d ●nergyREFERENCES1) F,J. Hump+reys ●nd K, Kalu. Acts Het,, 4, 917, (1990).2) D.G, Attwood ●nd P,?l, )iazzledine. Metallography, 9, 483, (1976),3) R. Soworby, E, Chu ●nd J’,L, Duncan, J, Strain Anal., 17, 95, (1982).4) P.R.Dawson, Personal Communication.5) L.!4, Clarebrough, M,E. Hargreaves ●nd!4,H, Loretto. Acts Met,, 6, 725, (1958),6) B. Hutchinson, S, Jonseon ●nd L, Ryde, Scripts Met , 23, 671, (1989),7) W.J, Poole, U.F. Kocks, R,E, Bolmaro ●nd J,D, Emburj, Proc, 12th Riso Int, Symp,on Materiala Sci,, cd, N. Hanson ●t ●l, , Denmark, 587, (1991),

On recrystallization in metal matrix composites

https://digital.library.unt.edu/ark:/67531/metadc1057810/m2/1/high_res_d/5161593.pdf

On recrystallization in metal matrix composites

Abstract

Similar works

Full text

Available Versions

UNT Digital Library