Zirconium In Nuclear Industry, 3-7 Feb 2013, Hyderabad

Study on Effect of Processing on Texture Development in Zirconium-2.5% Niobium Alloy Tubes

K Kapoor, S V Ramana Rao, K Itisri, B Prahlad, N SaibabaN Saibaba

Nuclear Fuel Complex, Hyderabad, INDIAkapoork@nfc.gov.in@ g

Critical Out-of-Pile Properties of Zirconium Alloy Tubes for Nuclear Application Chemical composition (alloy elements and Impurities)Mechanical propertiesRoom temperature and Elevated temperature tensileRoom temperature and Elevated temperature tensile Closed end burst (fuel tube)Hardness

C i (W t /St t l t d t t )Corrosion (Water/Steam at elevated temperature)Hydride orientationTextureMicrostructure (grain size, SPP-size and morphology)Dislocation densityFracture ToughnessFracture ToughnessCreep (structurals)Soundness by NDT (Ultrasonic and Eddy current )Vi l d S f fi i hVisual and Surface finishDimensional (OD, ID and WT)

Outline of the talk o Current understanding on role of texture in Zr-2.5Nb pressure tubeo Experimental Techniques used for Characterization of Textureo Results of Texture Development during Processing of Zr-2.5Nb pressure

tubes- Ingot processing (Comparison on 3 different routes)g p g (C p 3 )- Hot Extrusion (Comparison on 3 different routes)- Cold Working (Comparison on 3 different routes)

Heat treatment- Heat-treatmento Discussion

- Microstructure Development during the processing- Modeling of Texture using VPSC approach-Texture-microstructure relationship- SummarySummary

Introduction: Texture Development During Zr-alloy Tube Manufacture

Q-ratio

where, Q -ratio= ln ( t/ T ) / ln (d /D ) Erich Tenckhoff, STP 966 (1988)

Introduction: Role of Texture in Irradiation Creep in Zr-2.5% Nb Pressure Tubesp

b. U

nits

)Irr

ad. C

reep

(arb

fT-fR

INFERENCE: High Transverse Texture (basal pole in transverse direction) for reducing transverse creep (diametric expansion)

T R

R.A. Holt et.al , JNM 317 (2003)

Introduction: Role of Texture in Delayed Hydrogen Crackingy y g g

Threshold stress intensity for DHC:

DHC Velocity, da/dt = C1 exp.C2 F exp. (Q/RT), where C1 and C2 are microstructure and texture dependent parameters;

Kim, JNM 349 (2006)

microstructure and texture dependent parameters;

Introduction: Role of Texture in Hydride Orientation in the Zircaloy-4 Tubesy y

Extruded

TransverseFi l CWSR

Radial

Final CWSR

INFERENCE: High Radial Texture (basal pole in radial direction) for low radial hydride

Transversefraction

K. Vaibhaw et.al JNM, 383(2008) Radial

Introduction: R l f T t i St C i C kiRole of Texture in Stress Corrosion CrackingStress corrosion crack growth rate da/dt = C(KI)n

The KI and n are related to texture parameter

INFERENCE: High Radial Texture (basal pole in radial direction) for better SCC

Hwang, SK, Met. Trans. A 1991; 22A: 2247-56

INFERENCE: High Radial Texture (basal pole in radial direction) for better SCC

Introduction: Role of Texture in Mechanical anisotropy and pyThermal expansion

Related Property

Constituted equations Reference

Mechanical i t

(R*(ND - TD )2 + R*P*(TD - RD )2 + P*( )2}/P*(R 1) 2

K Linga Murty, Progress i N l E 48anisotropy P*(ND - RD )2}/P*(R+1) = g

2

R and P are texture dependentin Nuclear Energy 48 (2006)

Thermal expansion

Pref = fref P[0001] + (1- fref) P [0001] Kearns JJ. Report WAPD TM 472 1965;expansion WAPD-TM- 472, 1965;

Experimental: Macro and Micro Texture Measurement

Crystallographic Texture

Experimental Techniques

X-Ray DiffractionMACROTEXTURE

EBSD (SEM)MICROTEXTURE

GoniometerPowder Diffraction

Texture Quantification

Orientation Distribution Function

Pole FigureKearn’s ‘f’ parameter

Channeling Contrast

Microstructure and MicrostrainOrientation Distribution Function

CPF IPF %(hkil)<uvtw>

Microstructure and Microstrain

Experimental: Quantification of Crystallographic Texture- Kearn’s fQ y g p

The Kearn’s ‘f ’parameter is the fraction of basal poles oriented in the three principal directions i e Longitudinal Transverse and Normalthree principal directions i.e. Longitudinal, Transverse and Normal (fL, fT and fN) in the sample such that fL+ fT + fN = 1,

2/

0

2cos Vi

i

i

f

2

0

2 d . cos . sin ).( I

f

2

0

d . sin ).( I

f

Experimental:Quantification of of Crystallographic Texture: ODF and Pole fig.ODF R t tiODF Representation: For hexagonal crystal symmetry and triclinic sample symmetry, the dimension of the unit cube is

Key for crystallite directions (2= 0)

dimension of the unit cube is defined as {0 ≤ 1 ≤ /2, 0 ≤ ≤ /2, 0 ≤ 2 ≤ /3}

ODF Quantification: a) A texture component f(g) with {1, , 2} being the orientation ) p (g) {1, , 2} gb) Volume fraction of texture component f(g) = dv/V = 1/82 ∫∫∫f(g)dgwhere, dv/V is the volume fraction fraction of crystallite having an orientation in the range dg defined as {1, , 2}c) Pole Figure representation: An orientation in three dimensional space isc) Pole Figure representation: An orientation in three-dimensional space is represented by Euler angles as 1

hkl, hkl, 2hkl, can then may be expressed in terms

of pole density function as,

1Phkl(,) = hklhklhklhkl df 221 ),,(

21

ROUTE 1 (a and b) ROUTE  2  ROUTE 3

V A l i V A l i V A l i

Process Routes of Pressure Tube

INGOT PRO

Vacuum Arc melting Vacuum Arc melting Vacuum Arc melting↓ ↓ ↓

Hot Extrusion to Billet Forge I Double Forged

OCESSIN

G

↓ ↓↓

Beta quenching Beta quenching

↓ ↓Forge II Beta quenching

Hot

Processing

↓ ↓Hot Extrusion for Blank

(ER 1:8)Hot Extrusion for Blank

(ER 1:8)Hot Extrusion for Blank 

(ER 1:12)

↓ ↓ ↓ ↓↓ ↓ ↓ ↓

Cold Pro

Cold Pilger I Cold Pilger I Cold Pilger I Cold Pilger I

↓ ↓ ↓

Annealingα+β

Q hiAnnealingocessing and H

↓Quenching

↓ ↓↓

Cold Pilger II Cold Pilger II Cold Pilger IIHT ↓ ↓ ↓

Autoclave Ageing(HT) Autoclave Autoclave

Results: 1.0 Effect of Ingot Processing Route

Route 1: Ingot Extrusion to Billet -quenchStress relieve

Route 2: Ingot Hot forge to intermediate -quench Hot-forge to BilletR t 3 I t H t f t i t di t h H t f t Bill t hRoute 3: Ingot Hot forge to intermediate -quench Hot-forge to Billet -quench

(a1)

XRD patterns (a) Ingot (b) JCPDS (c) powder Ingot sample (d) Billet route 1 (e) Billet route 2, a1) ODF at IngotInference: Ingot processing texture is destroyed by beta quenching

Results: 2.0 Effect of Hot Extrusion RatioBeta Quenched Billet : : ROUTE 1a

Extrusion (ER1:8)

Mother Hollow ( )

Beta Quenched billet : : ROUTE 3

Extrusion (ER1:12)

Mother Hollow

Microstructure and Texture (EBSD) of As extruded (Route 1a)

Longitudinal sectionLongitudinal section

Transverse section

Pole Figure and ODF Section. Microstructure

Results: 2.0 Texture and Microstructure (EBSD) of as-extruded (Route 3) Microstructure( )

Pole Figure and ODF Section.

Longitudinal section

Transverse sectionTransverse section

Inference: Higher Extrusion ratio leads to higher Transverse Texture

Results: 3.0 Texture Evolution During Cold Deformation -Quenched billets: ROUTE 1 a

Extrusion (ER1:8)

1 Pilger (60% CW)

Anneal 823K

2 pilger (25% CW)

Stress relieve 673 KROUTE 1 a (Zr-2.5Nb/ Zircaloy-4)

(ER1:8) (60% CW) 823K (25% CW)

-Quenched billets: ROUTE 3 (Zr 2 5%Nb)

Extrusion (ER1:12)

Cold drawing ( 25 % CW)

Stress relieve 673 K

(Zr-2.5%Nb)

As-extruded I pass pilger + anneal II pass pilger + SRZr-2.5Nb fT/ fR 1.47 1.42 1.41

Route 1a: Texture Evolution (Single phase Vs Two-phase)

Zr 2.5Nb fT/ fR 1.47 1.42 1.41 Zircaloy-4 fT/ fR 1.12 0.53 0.37

Zr 2 5NbZr-2.5Nb

Zircaloy-4

Inference: No texture change with cold pilgering in Two-phase Zr-2.5Nb, while the texture change predominantly in single phase Zircaloy-4

Results: 3.0 Texture Kerns ‘f’ and ODF on Cold Deformation Kearns ‘f ‘ Parameter Route 1a Route 3

Condition fr ft fa Condition fr ft fa

Hot  extruded (ER 1:8) 0.38 0.56 0.06 Hot  extruded (ER 1:12) 0.29 0.66 0.05

I Pass Pilgered & Annealed

0.40 0.57 0.03 NA

ODFs (with 2 section at =0) for Route 3

II Pass Pilgered & Autoclaved

0.41 0.57 0.02Pilgered & Autoclaved 0.29 0.66 0.05

As-extruded As-autoclaved

Orientation Components

Volume fraction of orientationsExtruded I Pilger and anneal As-autoclaved

Route 1a Route 3 Route 1a Route 3 Route 1a Route 3(11 22)<1 100> 18 79 10 10 7 96 27 53 19 87(11-22)<1-100> 18.79 10.10 7.96

NA27.53 19.87

(11-24)<1-100> 2.79 4.25 4.95 8.13 7.6(33-61)<1-100> 3.70 4.86 2.03 10.09 15.85

Inference: No texture change with cold pilgering (two pass/single pass) in Two-phase Zr-2.5Nb

Results: 4.0 Texture Evolution Heat Treated Route-Quenched billets: ROUTE 1 b

Extrusion (ER1:9.4)

1 Pilger(41% CW)

α+βQuench

2 pilger(25% CW)

Ageing(HT)

Kearn’s ‘f’ Texture parameter (as aged) Microstructure

ROUTE 1 b (Zr-2.5Nb)

(ER1:9.4) (41% CW) Quench (25% CW)

fr ft faAs-extruded 0.38 0.56 0.06As- Quenched 0.33 0.37 0.35

Aged 0.36 0.50 0.14

Pole Figure and ODF (as aged)As- Quenched

AgedSaibaba et.al, 2010, under publication

Route 1a: Ingot Extrusion to final -quenchHot Extrude Cold Pilger

Stress relieve

Route 2: Ingot Hot forge to intermediate -quench Hot-forge to final

Results: Microstructure Development and Mechanical properties

Bill t St E t d d bl k Fi l t li

Final Mechanical PropertiesMicrostructural evolution

relieveRoute 3: Ingot Hot forge to intermediate -quench Hot-forge to final -quench

Billet Stage Extruded blank Final stress relieve

1% Elongation

Process 1 (samples 176)

2

UTS (in MPA)Process 1 (samples 176)

56 2 5 - 6 6 0

26

8749

302

0 50 100

12-14

16-18

20-22

%

No. of tubes

551

3716

62

0 20 40 60 80

4 5 0 - 4 8 5

4 8 5 - 5 2 0

5 2 0 - 5 5 5

5 5 5 - 5 9 0

5 9 0 - 6 2 5

UTS

No. of tubes

2% Elongation

Process 2 (samples 206)

4499

10

14 16

18-20

%

UTS (in MPA)Process 2 (samples 206)

365

5 5 5 - 5 9 0

5 9 0 - 6 2 5

S

143944

0 50 100 150

10-12

14-16%

No. of tubes 206

547

113

0 50 100 150

4 5 0 - 4 8 5

4 8 5 - 5 2 0

5 2 0 - 5 5 5

UTS

No. of tubes

Discussion: Morphological evolution of phase

Increasing time

Morphological evolution of rod shaped structures with thermo mechanical deformation [ by Cline, Ho and Weatherly]

Processingroute 1a and 3

Processingroute 2

Billet Stage Extruded blank Stage

Billet soaked at high temperature

Final Stage

Morphological evolution of phase during themo mechanical processing

Modelling: Texture in two-phase ( + ) Zr-2.5Nb alloy

a) Taylor-Bishop-Hill model Results on modeling of texture of ) y p

b) Self-Consistent Viso-Plastic modelZircaloy and Zr-2.5Nb [R A Lebenson and C N Tome, Acta. Mat. 1993]

Inference: FC model gives satisfactory results only in case of single phase Zircaloy-2 material

VPSC models texture well in case of Zr-2.5Nb and Zircaloy-2 materials

Modeling of Texture – application of VPSC Model on two-phase ( + ) Zr-2.5Nb alloyViscoplastic Self-consistent simulations based on Eshelby’s inclusion

problem Initial texture as inputpChoose slip and/or twin systems Choose CRSS and hardening parameters for individual slip and twin system Impose strain boundary condition (‘Q’ parameter for pilgering) Impose strain boundary condition ( Q parameter for pilgering)Match experimental and simulated texture

I l i

Homogeneous Equivalent Medium

Inclusion

C. N. Tome and R. Lebensohn, VPSC-7 manual 2008

General MethodologyModeling of Texture using VPSC approach: General methodology of Investigation

Material

Test/Deformation Process

S l Ch i i b XStructural Characterization by X-ray diffraction

Understanding D f ti

Bulk Texture from X-ray diffractionDeformation Mechanisms

Microtexture and Microstructure from EBSD

Simulations

Modeling of Texture – application of VPSC Model on two-phase ( + ) Zr-2.5Nb alloy

VPSC allows to use 2 site model, Consider a pair of alpha and betaMicrostructural morphology can be incorporated in simulations In addition to crystallographic texture, morphology of lamellas can also

be incorporated : random vs aligned

Aspect ratio in 3D

alpha

alphabeta

Morphology

Longitudinal directionLongitudinal direction

Modeling of Texture – application of VPSC Model on two-phase ( + ) Zr-2.5Nb alloy

Successful in showing difference in texture evolution for single phase and two-phase ( + ) Zr-2.5Nb alloy.

Kiran Kumar et al* showed similar results with negligible texture evolution in alpha phase of Zr-2.5% Nb during cold rolling Attributed to rigid body rotation of alphacold rolling. Attributed to rigid body rotation of alpha platelets

No strain partitioning between alpha and beta phase p g p pwith the beta phase accommodating all the strain

Gurao et al** incorporated morphology of microstructure in VPSC simulations of HCP + BCC TiNbZr alloy

*Kiran Kumar et al Acta Materialia 51 (2003) 625*Kiran Kumar et al. Acta Materialia 51 (2003) 625.**N. P. Gurao, PhD thesis IISc, Bangalore

Results of Modeling: Texture-microstructure relationshipp

In single phase materials direct grain to grain contact leads to full constraint on deformationcontact leads to full constraint on deformation

In two-phase material (with soft GB phase), the softer phase carries most of the strain.softer phase carries most of the strain.

Cold deformation of single phase material is accommodated by combination of twinning and slipy g p

Twinning is retarded due to lamellar morphology of HCP phase in two-phase Zr-2.5%Nb materialp p

Concluding Remarks Texture plays a dominant role in the in in-pile performance

of Zr-2.5Nb structural material. Ingot processing texture is destroyed by beta quenching Ingot processing texture is destroyed by beta quenching Processing flow sheet is tailored to give the required

texture in the tubing. High transverse texture for Zr-2.5Nb pressure tube is achieved by higher Extrusion Ratio.

No change in texture is observed during CW in Two-phase Zr 2 5Nb material Presence of second phase atphase Zr-2.5Nb material. Presence of second phase at the grain boundary influences the texture development.

VPSC model is used to explain the texture development p pduring cold working

ACKNOWLIDGEMENTS

Prof. N. P. Gurao, IIT(K) for help in Texture Modeling

Dr. Ubhi Singh Harvinder, Oxford Instruments, for help in EBSD

Thank Youhank You