Texture evolution analysis in oxide dispersion strengthened ferritic steel transformed by a tube pilgering process

(1)

HAL Id: cea-02437072

https://hal-cea.archives-ouvertes.fr/cea-02437072

Submitted on 13 Jan 2020

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Texture evolution analysis in oxide dispersion

strengthened ferritic steel transformed by a tube

pilgering process

E. Vakhitova, D. Sornin, Manuel Francois

To cite this version:

E. Vakhitova, D. Sornin, Manuel Francois. Texture evolution analysis in oxide dispersion strengthened ferritic steel transformed by a tube pilgering process. 18th International Conference on Textures of Materials (ICOTOM-18), Nov 2017, Saint George, United States. �cea-02437072�

(2)

TEXTURE EVOLUTION ANALYSIS IN OXIDE

DISPERSION STRENGTHENED FERRITIC STEEL

TRANSFORMED BY A TUBE PILGERING PROCESS

6 - 10 NOVEMBER 2017

12 OCTOBRE 2017 | PAGE 1

Elena VAKHITOVA

a

_{, D. SORNIN}

a

_{, M. FRANCOIS}

b

a_{DEN-SERVICE DE RECHERCHES MÉTALLURGIQUES APPLIQUÉES, CEA,}

UNIVERSITÉ PARIS-SACLAY, F-91191, GIF-SUR-YVETTE, FRANCE.

b_{UNIVERSITY OF TECHNOLOGY OF TROYES (ICD-LASMIS),}

F-10004, TROYES, FRANCE.

18th International Conference on Textures of Materials

ICOTOM 18, ST GEORGE (UTAH)

(3)

GENERAL CONTEXT

Core material for Sodium Fast Reactor (ASTRID) Gen IV (2030s)

Required properties:

Resistance to irradiation : low swelling

Resistance to high temperature corrosion

Mechanical properties: creep resistance

12 OCTOBRE 2017

| PAGE 2 18th International Conference on Textures of Materials | 10 NOVEMBER 2017

Analysis of microstructural and mechanical properties evolution

during thermomechanical processing

nuclear reactor core TEM

Y₂Ti₂O₇particles(1023_.m-3₎

[Klimiankou et al., 2004]

Hot forming

(4)

MOTIVATIONS // METHODS AND MATERIALS

| PAGE 3

Motivation:

 Characterization of structure and properties evolution of ODS steels during

“Mannesmann” pilgering

 Modeling of ODS steel behavior during the cold rolling

 Using the results of this study to improve rolling technology process

Materials and methods:

 ODS steel tubes with 9wt% Cr deformed by rolling process

 Analysis of the material behavior after each processing steps:

Hot Extrusion of powder material, Cold rolling and Heat treatments

Hot Extrusion (HE) Rolling 1 (R1)

Rolling 2 (R2)

Intermediate Heat Treatment (IHT6) (ferritic state – cooling rate 0,01°/s) Intermediate Heat Treatment (IHT1)

(ferritic state - cooling rate 0,03°/s)

Final Heat Treatment (FHT) (ferritic state – cooling rate 0,03 °/s)

Rolling 2 (R2 HT) scheme 1

scheme 2

Deformation history of 9%Cr ODS steel during the rolling process

Step Total deformations εp* (%) Q factor**

HE -/- -/-R1 110 1,4 R2 140 1,6 ** * 0

18th International Conference on Textures of Materials | 10 NOVEMBER 2017

Cr W Ti Ni O Y C Fe

9 0.9 0.2 0.2 0.1 0.1 0.08 Balance Chemical composition of ODS steel tubes (wt.%)

(5)

EBSD OBSERVATION RESULTS

 Initial Structure : isotropic, without preferred orientation

 Rolled samples : anisotropic structure with small elongated

grains according to the rolling direction

R1 IHT1 R2 R2 (HT) R2 FHT1 R2 (HT) FHT1 20µm x2000 20µm 20µm 20µm 10µm 20µm x2000 x2000 X4000 x2000 x2000 X2000 E x tr us ion / Ro lli ng Di rec ti on 20µm HE

Inverse pole figures maps IPF Y // RD for 9wt%Cr ODS steel at the different processing steps

111 101 100 HE R1 R2 IHT6 IHT1 FHT R2 HT 1 2

1

2

(6)

R1 IHT1 R2 R2 (HT) R2 FHT R2 (HT) FHT HE 111 101 100 zz (RD) θθ (ND) rr (TD)

<111> oriented grain disappear progressively during rolling steps

Dominant

<101> orientation after heat treatment

 Inverse Poles Figures of the ODS 9%Cr sample at different rolling steps

EBSD OBSERVATION RESULTS

HE R1 R2 IHT6 IHT1 FHT R2 HT 1 2

IPF Y // RD

1

2

Randomly oriented grains in recrystallized structure [Toualbi, 2012] ?

Unexpected texture!

(7)

 Texture Index (Gaussian approximation of 5° halfwidth)

 Strengthening of the α-fiber with plastic strain

 Reorientation of <001> and <111> oriented grains in the <101> during the thermal treatment

 Memory effect of deformation texture

0 5 10 15 20 25 HE R1 R2 R2 TTH T ex tur e inde x es (TI ) 0 5 10 15 20 25 HE R1 HT 6h HT R2 HT R2 TTH T ex ture index es (T I) HE R1 R2 R2 FHT HE R1 IHT6 R2(HT) R2(HT) FHT

1

2

HE R1 R2 IHT6 IHT1 FHT R2 HT 1 2

EBSD OBSERVATION RESULTS

(8)

TEXTURE EVOLUTION ANALYSIS

Beam Line: ESRF ID11 (XRD in transmission mode)

Beam Line manager: Jonathan WRIGHT

Photons energy range requested: 80,005 keV

Spot size requested: 200x200 µm

Impact of :



Initial texture ?



Holding time in furnace ?



Applied cooling rate ?

Thermal cycle for R1 and R2 samples

Initial texture

Holding time in furnace

Applied cooling rate

850 T (°C) 1050 800 25 400 R1 R2 2°C/min 50 °C /m in 50 °C /m in

- a scanned pole figure

600

Heating rate= 100°C/min

50

°C

/m

in

R1

60 min 60 min 20 min

time (min)

18th International Conference on Textures of Materials | 10 NOVEMBER 2017 | PAGE 7

RD

(9)

0 1 2 3 4 5 6 0 200 400 600 800 1000 1200 0 20 40 60 80 100 120 140 160 180 200 220 240 T e x tu re inde x T e mpe ra tu re [ °C] 25 min 100 °C/ m in



time (min)

SLOW COOLING / LOW DEFORMED SAMPLE (R1)



 → 

 → 

A_c1 F_s



| PAGE 8 ODF φ2 = 45°



_p

= 110%

α-fiber ( 110 // RD)

P-fiber ( {110}<122> // RD) Cu fiber ( {112}<111> // RD)

(10)

| PAGE 9

Temperature [°C]

100 1040

200 



TEXTURE EVOLUTION AS THE FUNCTION OF T [°C],

STRAIN, APPLIED COOLING RATE AND HOLDING TIME

6

25min

3 6 6

60min

3 6 12

60min

5 12

 = 110%

Slow Cooling

 = 110%

Fast Cooling

 = 250%

Fast Cooling





_’

(t)



(t)





_’

(t) 12



(t)

Slow Cooling

(11)

-

Texture memory was confirmed during phase transformation at the slow cooling rate

-

Texture is identified for the first time in austenitic domain and noted to be stable during HT

-

The higher is the strain, the more remarkable is the texture level after heat treatment

-

Possible mechanisms of variant selection (typically explained by K-S relation [1]):

(1) transformation strain; (2) precipitates; (3) special boundaries formed upon heating/cooling

CONCLUSIONS ON IN-SITU XRD TEXTURE

ANALYSIS

| PAGE 10 [1] Kurdjumov G, Sachs G. Z Phys 1930; 64:325.

 Synchrotron in-situ XRD crystallographic texture analysis during phase transformation

0 1 2 3 4 5 6 7 8 9 100 840 1035 1040 1040 700 650 200 T extu re in d ex Temperature [°C]





’

Fast cooling

250% high deformed sample

110% low deformed sample

0 1 2 3 4 5 6 7 8 9 100 840 1035 1040 1040 700 650 200 Te xture ind ex Temperature [°C]





Slow cooling

250% high deformed sample

(12)

CONCLUSIONS ET PERSPECTIVES

| PAGE 11

Conclusions:

1. Analysis of the microstructure at each production step

 Influence of the deformation degree (rolling sequence) and heat treatments on texture evolution  Texture study of ferrite and austenite phases by synchrotron radiation

 Variant selection rule is considered to explain texture memory effect

→ Recommendations for industrial application (cooling rate, holding time, forming sequence, mechanical properties, etc.)

Perspectives:

1. Identification and explanation of observed fibers in austenite domain

2. Precipitations role on texture memory at the experimental and simulation parts

3. Texture modeling using Visco-Plastic Self-Consistent model (VPSC) :

 Modification of the hardening law taking into account precipitation and its influence on selection of slip systems  Improvement of the simulation on cyclic loading

Communications:

• E. Vakhitova, D. Sornin, F. Barcelo, M. François, Texture evolution in Oxide Dispersion Strengthened (ODS) steel tubes during pilgering process, Journal of Nuclear Materials, 494, pp.20-28, (2017)

• Texture Evolution Analysis in Oxide Dispersion Strengthened Ferritic Steel Transformed by a Tube Pilgering Process, 18th International Conference on Textures of Materials (ICOTOM-18), November 6-10, 2017, St George, Utah

(13)