Reconstruction of austenite orientation map based on ... - alemi.ca

<strong>Reconstruction</strong> <strong>of</strong> <strong>austenite</strong> <strong>orientation</strong> <strong>map</strong><strong>based</strong> on martensite / bainite <strong>orientation</strong>data and application to ausformingG. Miyamoto, N. Takayama, T. FuruharaInstitute for Materials Research, TohokuUniveristy, Japan’10 / 6 / 4 Max Planck (Dusseldorf)1

Outline1. Introduction <strong>of</strong> ausforming2. Measurement <strong>of</strong> <strong>orientation</strong> relationshipbetween martensite & bainite / <strong>austenite</strong>matrix.3. <strong>Reconstruction</strong> <strong>of</strong> <strong>austenite</strong> <strong>orientation</strong> <strong>map</strong><strong>based</strong> on ferrite <strong>orientation</strong> <strong>map</strong> <strong>of</strong>martensite and bainite structures, andapplication to ausforming treatment.

Crystallographic feature <strong>of</strong> lath martensite / bainiteLath martensite holds near K-S O.R. with γ matrixKurdjumov-Sachs O.R.(111) γ // (011) α’ : habitplane[101] γ // [111] α’24 equivalent variantRefinement <strong>of</strong>substructureImprovingpropertyLow carbon martensiteAusforming treatmentTo obtain martensite/bainitestructures transformed fromdeformed & unrecrystallizedγImprovement <strong>of</strong> toughnessand strength due to increasingdislocation density and refiningsubstructure.3

Effects <strong>of</strong> ausforming microstructureFe-9%Ni-0.15%C alloy transformed at 623Knon deformed γ deformed γH.Kawata, et al.,Mater. Sci. Eng. A(2006)ausforming? deformation structure in γ? How it affectstransformed structure?transformationtransformationWant to reconstructmatrix structure!!Non ausformed bainite50% ausformed bainite4

<strong>Reconstruction</strong> <strong>of</strong> γ grain <strong>map</strong> Cayron et al., Mater. Char., 57(2006), 386 Morimoto et al., Tetsu to Hagane, 93(2007), 591C. Cayron et al.α grain <strong>map</strong>1 Based on averaged <strong>orientation</strong> <strong>of</strong> each ferritegrain, mis<strong>orientation</strong> matrices at high angleboundary in lath martensite structure arecalculated.3 When the mis<strong>orientation</strong> matrix coincide withthat predicted by assuming K-S(N-W) O.R.within a permissible angle, ferrite grainsneighboring this boundary is judged asforming from the same γ grain.γ grain <strong>map</strong>Previous reconstruction method have beenapplied to only non-deformed martensite.AimDeveloping new method which can reconstructdeformation structure in γ grain5

Outline1. Introduction <strong>of</strong> ausforming2. Measurement <strong>of</strong> <strong>orientation</strong> relationshipbetween martensite & bainite / <strong>austenite</strong>matrix.3. <strong>Reconstruction</strong> <strong>of</strong> <strong>austenite</strong> <strong>orientation</strong> <strong>map</strong><strong>based</strong> on ferrite <strong>orientation</strong> <strong>map</strong> <strong>of</strong>martensite and bainite structures, andapplication to ausforming treatment.

OR between martensite(M) / in ferrous alloysAlloyType <strong>of</strong> MAngle(111)~(011)Angle(-101)~(-1-11)Fe-3.1Cr-1.5C *1 Thinplate{225} 0.3° 2.8°MethodFe-22Ni-0.8C *1 Thinplate 1° 2.5°Laue(X-ray)Fe-32Ni *1 Lenticular 1° 4.3°Fe-20Ni-5Mn *2 lath 0° 3.9° SADP(TEM)*1 : C.M. Wayman, Adv. Mater. Res., 3(1968), 147.*2 : B.P.J. Sandvik, C.M. Wayman, Metall. Trans., 14A(1983), 809.7

OR between martensite(M) / in ferrous alloysAlloyType <strong>of</strong> MAngle(111)~(011)Fe-3.1Cr-1.5C *1 Thinplate{225} 0.3° 2.8°Angle Low carbon martensite *3(-101) (Fe-0.1C-2Si) Method~(-1-11)retainedγFe-22Ni-0.8C *1 Thinplate 1° 2.5°Laue(X-ray)Fe-32Ni *1 Lenticular 1° 4.3°Fe-20Ni-5Mn *2 lath 0° 3.9° SADP(TEM)Kelly, et al, (1990)Fe-0.1C-2Si *3KikuchiFe-0.3C-3Cr lath 0° 2.5°diffraction(TEM)-2Mn-0.5Mo *3Accurate data <strong>of</strong> OR for lath martensite in low carbon steelsare few, because <strong>austenite</strong> is difficult to be retained.*1 : C.M. Wayman, Adv. Mater. Res., 3(1968), 147.*2 : B.P.J. Sandvik, C.M. Wayman, Metall. Trans., 14A(1983), 809.*3 : P.M. Kelly, et al, Acta Metall. Mater. 38(1990), 1075.8

ExperimentalAlloy(mass%)15C Fe-0.15%C -1.5%Mn-0.2 %Si-0.03%NbS45C Fe-0.44%C-0.86%Mn-0.26%SiHeataustenitizationtreatment (1423~1473K,0.6ks)Water quenchOri. analysis SEM / EBSD15CS45C100m100m9

O.R. determination <strong>based</strong> on EBSD measurementG. Miyamoto et. al, Scr. Mater. (2009)Low carbon martensiteAnalyzed region ismanually croppedpole figureExperimental dataFitting procedureOrientation <strong>of</strong>M(B)(exp)Differences are calculated.■ fittingO.R. ×γ<strong>orientation</strong>50mO.R. and γ <strong>orientation</strong>matrices are determined byleast square fitting.10

O.R. between lath M / γ(15C(M))γ<strong>orientation</strong>(fitting)M <strong>orientation</strong>(exp.)O.R. is re-indexedby considering variantK-S O.R.(111) γ // (011) α[101] γ // [111] α[121] γ // [211] α001γ stereographic projection-101 γ001 γ010 γ111 γClose-packed plane100 γClose-packed direction

OR between lath M / γAngle between([-11-1], [-101]) directions/ degreeMeasuring three different grainsfor each specimen5.04.03.02.01.0N-WS45C(M S = 593K)KellyG-T15C(M S = 713K)K-S00 1.0 2.0 3.0 4.0Angle between ((011), (111))planes/ degree• Scattering in OR is lessthan ±0.3º in one alloy→ high accuracy• Close-packed planes anddirections are not parallel.• The higher Mstemperature, the largerangle between closepacked planes.12

Outline1. Introduction <strong>of</strong> ausforming2. Measurement <strong>of</strong> <strong>orientation</strong> relationshipbetween martensite & bainite / <strong>austenite</strong>matrix.3. <strong>Reconstruction</strong> <strong>of</strong> <strong>austenite</strong> <strong>orientation</strong> <strong>map</strong><strong>based</strong> on ferrite <strong>orientation</strong> <strong>map</strong> <strong>of</strong>martensite and bainite structures, andapplication to ausforming treatment.

γ <strong>orientation</strong> determination <strong>based</strong> on EBSD measurementLow carbon martensiteDecreasing size <strong>of</strong> cropped area+automatic cropping procedure<strong>map</strong>ping <strong>of</strong> local γ<strong>orientation</strong>50m14

Effect <strong>of</strong> O.R. used for reconstructionExperimentally determined O.R.(Δθ CPP = 1.5 o , Δθ CPD = 2.7 o )K-S O.R.(Δθ CPP = 0 o , Δθ CPD = 0 o )20μm20μmWhite line twin boundaryBlack line other H.A.G.BWhen K-S O.R. is used, mis-indexing as twin is frequently happened.20

NWKellyExp.KS6 CPD(deg)4200 1 2 3 4 5 CPP(deg)21

Reason for mix-indexing <strong>of</strong> twin <strong>orientation</strong>fcc → bcc transformationbcc → fcc reconstructionV5V4V5V4V6V3V6V3(111)γ[-101]γtwin(011)α[-1-11]αV1V2(011)α[-1-11]αV1V2Non-parallel relation between close-packed planes loses twin symmetry?22

<strong>Reconstruction</strong> <strong>of</strong> γ <strong>orientation</strong> <strong>map</strong> from 30% ausformed martensiteα <strong>orientation</strong> <strong>map</strong>EBSD0.2μm stepCondition2.0μm mesh & stepO.R.Δθ CPP= 1.5 oΔθ CPD= 2.7 oC.A.20μm23

<strong>Reconstruction</strong> <strong>of</strong> γ <strong>orientation</strong> <strong>map</strong> from 30% ausformed martensite<strong>Reconstruction</strong> <strong>of</strong> γ <strong>orientation</strong> <strong>map</strong>12C.A.20μmmis<strong>orientation</strong>(deg.)mis<strong>orientation</strong>(deg.)10501051- Point to point- Point to origin200 20 40 60position(μm)24

<strong>Reconstruction</strong> <strong>of</strong> γ <strong>orientation</strong> <strong>map</strong> from non deformed bainiteα <strong>orientation</strong> <strong>map</strong>γ <strong>orientation</strong> <strong>map</strong>50μm50μmEBSD(0.5μm step)Condition(5.0μm mesh, 2.5μm step)O.R.(Δθ CPP= 1.3 o , Δθ CPD= 2.9 o )White lineBlack linetwin boundaryother H.A.G.B25

<strong>Reconstruction</strong> <strong>of</strong> γ <strong>orientation</strong> <strong>map</strong> from 30% ausformedbainiteα <strong>orientation</strong> <strong>map</strong> γ <strong>orientation</strong> <strong>map</strong> γ-KAM <strong>map</strong>(Δθ=15 o )50μm50μm50μmEBSD(0.5μm step)Condition(5.0μm mesh, 2.5μm step)O.R.(Δθ CPP= 1.3 o , Δθ CPD= 2.9 o )White lineBlack linetwin boundaryother H.A.G.B26

SummaryNew methods determining M・B/γ O.R. and reconstructing γ<strong>orientation</strong> are developed.O.R. measurement•Orientation relationship between M / γ and B / γ can be determinedprecisely within an error <strong>of</strong> 0.5degrees <strong>based</strong> on EBSD measurementwithout retained <strong>austenite</strong>.•Close-packed planes and directions <strong>of</strong> martensite and bainite are notparallel. Angular deviation between close-packed planes decreaseswith an decrease in Ms temperature.γ <strong>orientation</strong> reconstruction•Mis-indexing <strong>of</strong> twin <strong>orientation</strong> frequently happens when K-S or N-WO.R. are used for reconstruction possibly because <strong>of</strong> mirror symmetry<strong>of</strong> 111γ // 011α relation. By using experimentally determined O.R.,frequency <strong>of</strong> the mis-indexing is reduced largely.•Deformation structure in γ can be reconstructed successfully and beanalyzed mis<strong>orientation</strong> pr<strong>of</strong>ile or KAM analysis.27

Mis<strong>orientation</strong> pr<strong>of</strong>ile <strong>of</strong> lath martensiteV1/V2,3,4,5,6NW64 811,131621249,192,3,5KSExact4 8 11,1316212418,2218,22710,141717710,149,19612,15,20,2315,2312,203,520.030.020.0100 10 2040 50 6028

Martensite and bainite structuresTransformation temperature( o C)ferrite+<strong>austenite</strong>Martensite<strong>austenite</strong>Degen.pearliteLamellar pearliteBainite trans. tem. rangeUpper bainiteLower bainiteLath martensitebainiteCarbon content (mass%)Ohmori, Honeycombe: Proc. Int. Conf. Sci. & Technol.<strong>of</strong> Iron and Steels, Suppl. Trans. ISIJ, 11 (1971), 1160.29

Simple <strong>orientation</strong> relationship in fcc → bcc transformationFCC(γ:<strong>austenite</strong>)BCC(α:ferrite, martensite,bainitic ferrite···)(111)[110] // [100][101]// [111](011)Nishiyama-Wassermann(NW)(111) // (011)[110] // [100]Kurdjumov-Sachs(KS)(111) // (011)[101] // [111]30

FCC → BCC shear transformationmatrix(FCC)Product phase(BCC)Bain correspond.[001] // [001]Invariant plane(no strain&rotation)Lattice correspond.(Bain distortion)Lattice invariant def.(slip or twin)Rigid-body rot.F(shape change) = R(Rigid-body rot.) ・ B(Bain distortion) ・ P(lattice invariant def.)Determine O.R.31

Notice:OR determined in this method<strong>austenite</strong>martensiteOR-type1OR with respect to <strong>orientation</strong>deformed for accommodation.(TEM/Kikuchi analysis)OR- type 2OR with respect to initial <strong>orientation</strong>(X-ray analysis)OR in present study→OR232

Mis<strong>orientation</strong> pr<strong>of</strong>ile <strong>of</strong> lath martensiteN-WK-SExp.V1/ V4V1 / V2,V3,V5,V60 10 20 40 50 6017FrequencyObtained by OIM analysisfor low carbon martensite0 10 20 40 50 60Mis<strong>orientation</strong> angle(degrees)33

再 構 築 結 果 に 及 ぼすメッシュ、ステップサイズの 影 響 (30% 加 工 変 態 途 中 B)Mesh-step2x22x13x1.5 4x25x2.534

変 態 温 度 による 方 位 関 係 の 変 化F( 外 形 変 化 ) = R( 剛 体 回 転 ) ・ B(ベイン 変 形 ) ・ P( 格 子 不 変 変 形 )方 位 関 係 を 決 めるLow Temp.(less plasticaccommodation)B+P +RHigh Temp.(more plasticaccommodation)B+P +R( 小 )More plastic accommodation leads toapproaching Bain O.R.35

光 顕レンズマルテンサイトFe-33Ni 合 金薄 板 状 マルテンサイトFe-30Ni-0.45C 合 金SEM方 位 マップMAMA方 位 差 マップ0゜ 方 位 差5゜

ラスマルテンサイト(Fe-20Ni-5Mn 合 金 )光 顕A方 位 マップ方 位 差 マップAAMMMGB20m20mラスの 片 側 に大 きな 方 位 差