New Methods in Steel Design Wolfgang Bleck

Collaborative Research Center SFB 761

„Steel – ab initio; quantum mechanics guided design of new Fe based materials”

Wolfgang Bleck 2

Outline

• Introduction

• New modeling tools

• New characterization tools

• New processes

• Conclusions

Wolfgang Bleck 3

Decisions and Methods in Material Development

high

low

Risk Stage of development

HSLA AHSS HMnS

Industrial application 2010 1990 1970

Modeling 2000 1990 1980

Material; Time

HSLA: High Strength Low Alloy AHSS: Advanced High Strength Steels HMnS: High Manganese Steels

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Comparison Strength – Formability of different steel concepts

Strength

Form

abili

ty

High-Mn-Steels

(austenitic steels)

ferritic

steels

ferritic multiphase steels

Medium-Mn-Stähle

(austenitic

multiphase steels)

AHSS = Advanced High-Strength Steels

Wolfgang Bleck 5

Deformation Mechanisms in High Manganese Steels

g

k k

k

k

k

k k

T k T T

T

T T

T

T T

T T T T T T

T

T T

T

T T T Transformation

during

deformation

Twinning

during

deformation

Dislocation

generation and

reactions

Dislocation

channels by

intermetallics

SLIP TRIP TWIP MBIP

SLIP: Dislocation slip TRIP: transfomation induced plasticity TWIP: twinning induced plasticity MBIP: Microband induced plasticity

T T

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Outline

• Introduction

• New modeling tools

• New characterization tools

• New processes

• Conclusions

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Deformation mechanisms I – Method development

SFE-Concept 2007

Carbon content

Ma

ng

an

ese c

on

ten

t

TRIP: transfomation induced plasticity TWIP: twinning induced plasticity

a‘ –Martensite e – Martensite SFE: Stackingfaultenergy A. Saeed-Akbari, L. Mosecker, A. Schwedt, W. Bleck:

Metall. Mater. Trans. A, 43A (2012) 1688-1704

2D-Mechanism map 2011

Carbon content

Ma

ng

an

ese c

on

ten

t

+1.5 wt.-%

Aluminum

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Deformation mechanisms II – Method development

SFE-Concept 2007

3D-Mechanism map 2014

TRIP: transfomation induced plasticity TWIP: twinning induced plasticity MBIP: MicroBand Induced Plasticity

W. Song, T. Ingendahl, W. Bleck:

Acta Metall. Sin. (Engl. Lett.), 27 (2014) 3 546-556

A. Saeed-Akbari, L. Mosecker, A. Schwedt, W. Bleck:

Metall. Mater. Trans. A, 43A (2012) 1688-1704

2D-Mechanism map 2011

Carbon content

Ma

ng

an

ese c

on

ten

t

+1.5 wt.-%

Aluminum

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Fe-Cr-Mn-N

Patent: EP 14162191.2. “Austenitic stainless steels“ Europäische Patentanmeldung

Publication: L. Mosecker and A. Saeed-Akbari, Sci. Technol. Adv. Mater. 14 (2013) 1-14

Adoption of the SFB method to:

Steel and process development in only 3 years.

New material and process meet benchmark properties.

Materials and process design for stainless TWIP steel

Method

Development Materials

Application Materials

Processing

industrial process

different alloy system

Transfer project stainless TWIP steels I

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Fe-Cr-Mn-N Request: YS > 500 MPa, A > 40%

Patent: EP 14162191.2. “Austenitic stainless steels“ Europäische Patentanmeldung

Publication: L. Mosecker and A. Saeed-Akbari, Sci. Technol. Adv. Mater. 14 (2013) 1-14

Method

Development Materials

Application Materials

Processing

Transfer project stainless TWIP steels II

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Enthalpy of solutions

of C in Fe-Mn-Octahedron

Properties I

Steel denomination DIN EN 10027-1 and -2: TWIP: X60Mn18 TWIP Al: X60MnAl17-1 stainless steel: X5CrNi18-10

Fe Mn

Flow curves

X5CrNi18-10

X60MnAl17-1

X60Mn18 TWIP

TWIP Al

stainless steel

True plastic strain / -

Tru

e s

tre

ss / M

Pa

Experiment ab initio simulation

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Modelling approach yield strength:

Properties II – new interpretation of results

Solid solution hardening

sy (MPa) = 228 + 187(wt%C) - 2(wt%Mn) O. Bouaziz, H. Zurob, B. Chehab, J. D. Embury, S. Allain, M. Huang:

Materials Science and Technology 27 (2011) 707-709.

Flow curves

Short range order + microstructure

sSRO =M tSRO = M (Erandom – ESRO) / b3

sy (MPa) = 90 + sSRO + 11,3 d-1/2

J.-H. Kang: T. Ingendahl, J. von Appen, R. Dronskowski, W. Bleck:

Materials Science and Engineering A (2014) 122-128

Steel denomination DIN EN 10027-1 and -2: TWIP: X60Mn18 TWIP Al: X60MnAl17-1 stainless steel: X5CrNi18-10

X5CrNi18-10

X60MnAl17-1

X60Mn18 TWIP

TWIP Al

stainless steel

True plastic strain / -

Tru

e s

tre

ss / M

Pa

Experiment Constitutive model

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Outline

• Introduction

• New modeling tools

• New characterization tools

• New processes

• Conclusions

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Characterisation – quantitative analysis on nm-scale

STEM / TEM

Target preparation

APT

3D-Element distribution Grain boundaries Orientation

FIB: Focussed Ion Beam STEM: Scanning Transmission Electron Microscope APT: Atom Probe Tomography Herbig et al: Physical Review Letters 112 (12) 2014

FIB

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Fe-30Mn-8Al-1.2C wt.

K-Phase no K-Phase

Microstructure – local equilibrium

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nm - Precipitates of k-Phase

DESY

Synchrotron Diffraction

(001)κ

APT

Atom Probe Tomography

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Outline

• Introduction

• New modeling tools

• New characterization tools

• New processes

• Conclusions

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Material Design

Process chain for the

production of Fe-Mn-Al-C

Fe-Mn-Al-C-Crashboxen

with different heat treatment

SFE: Stackingfaultenergy

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Materials and Process Design I

Mechanismenorientiertes Werkstoff- und Prozessdesign

Christian Haase

O. Bouaziz, C.P. Scott, G. Petitgand: Scripta Mater., 60 (2009) 714-716.

H.T. Wang, N.R. Tao, K. Lu: Acta Mater., 60 (2012) 4027-4040.

C. Haase et al.: Met. Mater. Trans. A, 44 (2013) 4445-4449.

Deformation Twins

before cold rolling after cold rolling after recovery annealing

Substitution of recrystallization annealing by recovery annealing

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Materials and Process Design II

50 % + 550 °C/30 min 40 % + 550 °C/1 h

1 µm 1 µm

RX

Twin boundaries are heat resistant C. Haase et al.: Acta Mater., 80 (2014) 327-340.

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Materials and Process Design III

Variation of rolling degree and annealing parameters

allows the adjustment of final mechanical properties

CR: cold rolled RC: recovered RX: recrystallized

C. Haase et al.: Acta Mater., 80 (2014) 327-340.

C. Haase et al.: Adv. Mater. Res., 922 (2014) 213-218.

0 10 20 30 40 50 60 700

200

400

600

800

1000

1200

1400

Te

ch

nis

ch

e S

pa

nn

un

g (

MP

a)

Technische Dehnung (%)

0 10 20 30 40 50 60 700

200

400

600

800

1000

1200

1400

Technis

che

Spann

ung

(M

Pa)

Technische Dehnung (%)

0 10 20 30 40 50 60 700

200

400

600

800

1000

1200

1400

Te

ch

nis

ch

e S

pa

nn

un

g (

MP

a)

Technische Dehnung (%)technical strain (%)

tech

nic

al str

ess (

MP

a)

Y

ield

str

ength

0.2

% (

MP

a)

fracture strain (%)

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Outline

• Introduction

• New modeling tools

• New characterization tools

• New processes

• Conclusions

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Nano-Engineered Steels

g

k k

k

k

k

k k

T k T T

T

T

T T

T

T T T T

T T T T T T T T T T

T

T T

T

T

T T T T T

Transformation

during

deformation

Twinning

during

deformation

Transformation

+

precipitation

Dislocation

channels by

intermetallics

Bainite TRIP TWIP MBIP

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Microstructure length scales of different steels

1 m

conventional steel

TMP

UFG

NS

Thermo Mechanically Processed

Ultra Fine Grain

Nanostructured steels

10-3 m

10-6 m

10-9

nm

Quelle: Müller Weingarten AG

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Vision I: Quantitative Understanding of Parameters

bcc

fcc

hcp

Crystall structure

FM

PM

Magnetism

SLIP

TRIP

TWIP

MBIP

T T

k k

k

k

k

k k

T k T T T

T T

T

T

T T T T T T

T

T T

T

T

Deformation mechanisms

Multiphases

α‘ retained γ

g a’

Wolfgang Bleck 26

str

ess s

[M

Pa]

0 20 40 60 80 100 strain e [%]

TRIP

Steel

TWIP Steel

Vision II: Individual adjustment of mechanical properties for

stress exposed optimized components

source: Future Steel Vehicle, World Auto Steel Report

New quality level in

material development

New Methods in Steel Design Wolfgang Bleck

Collaborative Research Center SFB 761

„Steel – ab initio; quantum mechanics guided design of new Fe based materials”