J. Mola, I. Jung, J. Park, D. Chae, B.C. De Cooman, Ridging Control in Transformable Ferritic Stainless Steels, Metall. Mater. Trans. A. 43 (2012) 228–244.

AlN , [001] Z.A.

000

110

010

100

0.5 μm

000020

220200

M23C6 , [001] Z.A.

0.5 μm

AlN , [100] Z.A.

000001

011010

0.5 μm

Analysis of Precipitates: AlN, M23C6

AlN: 𝑃63𝑚𝑐, a=0.311 nm, c=0.498 nm

M23C6: Fmത3𝑚, a=1.05 nm

Hot rolled strip of

Fe16Cr0.5Mn0.1Ni0.1Al0.07C0.03N

(mass-%) ferritic stainless steel

BF, SAD

2 1 / n m2 1 / n m

113 ZA of M23C6

113 ZA of M23C6

422

422

220422

422

220

311 ZA of M23C6

311 ZA of M23C6

2-4-22-2-4

0-22 2-4-2

2-2-4

02-2

0.2 µm

Twinned M23C6 precipitates in a 16%Cr ferritic stainless steel

J. Mola, Ridging Resistance and Formability in the AISI 430 Transformable Ferritic Stainless Steel, doctoral dissertation, POSTECH, South Korea, 2012.

Analysis of Precipitates: Twinned M23C6

BF, DF, SAD

AlN

AlN

J. Mola, I. Jung, J. Park, D. Chae, B.C. De Cooman, Ridging Control in Transformable Ferritic Stainless Steels, Metall. Mater. Trans. A. 43 (2012) 228–244.

STEM images and EDS

analysis of AlN and M23C6

precipitates in a hot rolled strip

of

Fe16Cr0.5Mn0.1Ni0.1Al

0.07C0.03N (mass-%) ferritic

stainless steel

M23C6

Analysis of Precipitates: AlN, M23C6

STEM, EDS

Zone axis : [3,5,-1]

35-1 Z.A. of bcc // 112 Z.A. of hcp

1-1-2 bcc 3-2-1 bcc

2-11 bcc

-10-3 bcc

Orientation Relationship

(110)bcc // (001)hcp

<111>bcc // <110>hcp

J. Mola, Ridging Resistance and Formability in the AISI 430 Transformable Ferritic Stainless Steel, doctoral dissertation, POSTECH, South Korea, 2012.

Analysis of Precipitates: M2NM2N precipitates in a 16%Cr ferritic stainless steel

M2N: 𝑃63/𝑚𝑚𝑐, a=0.274 nm, c=0.444 nm BF, SAD

Orientation Relationship

(110)bcc // (001)hcp

<111>bcc // <110>hcp

J. Mola, Ridging Resistance and Formability in the AISI 430 Transformable Ferritic Stainless Steel, doctoral dissertation, POSTECH, South Korea, 2012.

-11-1 hcp

-01-1 hcp

-100 hcp

-1-10 bcc

110 bcc

Elongated M2N precipitates in a 16%Cr ferritic stainless steel

Analysis of Precipitates: M2N

BF, SAD

R. Rahimi, B.C. De Cooman, H. Biermann, J. Mola, Microstructure and mechanical properties of Al-alloyed Fe–Cr–Ni–Mn–C stainless steels, Mater. Sci. Eng. A. 618 (2014) 46–55. doi:10.1016/j.msea.2014.09.001.

Faulted M7C3 carbides in an Fe17Cr6Mn3Ni4Al0.45C duplex stainless steel

Analysis of Precipitates: M7C3

BF, SAD

Faulted

Q. Huang, B.C. De Cooman, H. Biermann, J. Mola, Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic–Martensitic Stainless Steels, Metall. Mater. Trans. A. 47 (2016) 1947–1959. J. Mola, B.C. De Cooman, Quenching and Partitioning (Q&P) Processing of Martensitic Stainless Steels, Metall. Mater. Trans. A. 44 (2013) 946–967.

Analysis of Precipitates: M3C

BF

DF1

DF2

Dark field imaging of a tempered

Fe13Cr0.3C martensitic

stainless steel using two different

cementite reflections

BF, DF, SAD

-200

-2-401

2402

011

-2201

-2202

-20012002

0-201 0202

Z.A.: [0-11]//[001]1//[001]2Z.A.: [0-11]//[001]1//[001]2

Orthorhombic

M3C ():

a= 0.509 nm

b= 0.674 nm

c= 0.452 nm

Bagaryatski O.R.:

{112} // {010}<01-1> // <001>

SAD pattern of martensite and

two cementite (θ) variants

0.5 m

0.3 μm

A

B

R. Rahimi, P. Pekker, H. Biermann, O. Volkova, B.C. De Cooman, J. Mola, Volumetric changes associated with B2-(Ni,Fe)Al dissolution in an Al-alloyed ferritic steel, Mater. Des. 111 (2016) 640–645. doi:10.1016/j.matdes.2016.09.033.

011111

100

B2 0ത11 Z.A.

Ferrite 0ത11 Z.A.

(A)

(B)011

200

211

B2-(Ni,Fe)Al intermetallics exhibiting a cube-on-cube O.R. with the ferritic matrix

Fe17Cr6Mn9Ni7Al0.46C ferritic stainless steel

Only weak

B2 reflections

Analysis of Precipitates: B2 BF, SAD

a)

c)

d)SAD pattern of c)

111

002

113

222

004e)

Analysis of Precipitates: VN

M. Wendler, B. Reichel, R. Eckner, O. Fabrichnaya, L. Krüger, A. Weiß, J. Mola, Effect of Vanadium Nitride Precipitation on Martensitic Transformation and Mechanical Properties of CrMnNi Cast Austenitic Steels, Metall. Mater. Trans. A. 47 (2016) 139–151.

20 nm

30 nm

SAD pattern of (c)

VN precipitates in an

Fe15Cr6Mn3Ni0.65V0.5Si

0.11C0.24N austenitic stainless

steel

HRTEM, SAD

0.4 µm

Recrystallization / Precipitation

TEM montage of ferrite and Cr carbides and

nitrides in an

Fe16Cr0.4Mn0.1Ni0.04C0.04N ferritic

stainless steel

Annealing time: 30 s + 30 s

J. Mola, E. Seo, I. Jung, B.C.De Cooman, J. Park, Cold rolling of α+ α′ dual-phase microstructure in transformable ferritic stainless steel, in: Proceedings of 7th Eur. Stainl. Steel Conf. Sci. Mark., Como, Italy, 2011.

BF

J. Mola, E. Seo, I. Jung, B.C.De Cooman, J. Park, Cold rolling of α+ α′ dual-phase microstructure in transformable ferritic stainless steel, in: Proceedings of 7th Eur. Stainl. Steel Conf. Sci. Mark., Como, Italy, 2011.

1 µm

TEM montage of ferrite and Cr carbides and

nitrides in an

Fe16Cr0.4Mn0.1Ni0.04C0.04N ferritic

stainless steel

Annealing time: 30 min

Recrystallization / Precipitation

BF

Recrystallization of Martensite and Ferrite

J. Mola, B.C. De Cooman, J. Park, Recrystallization behavior of α′ martensite in transformable ferritic stainless steels, in: Proceedings of 7th Eur. Stainl. Steel Conf. Sci. Mark., Como, Italy, 2011.

0.5 µm

(a)(b)

(c)

(d) (e)

0.5 µm

1 µm

0.2 µm

Rex.

Recovered

In-lath

precipitates

Twin

boundary

precipitates

Twin

boundary

precipitates

0.5 µm

(a)(b)

(c)

(d) (e)

0.5 µm

1 µm

0.2 µm

Rex.

Recovered

In-lath

precipitates

Twin

boundary

precipitates

Twin

boundary

precipitates

Difference in the recrystallization behavior of ferrite and martensite in a cold-rolled

Fe16Cr0.4Mn0.1Ni0.04C0.04N ferritic-martensitic stainless steel

BF DF

α

αʹ

Annealing

conditions:

rapid heating to

750 °C and

immediate

cooling

BF, DF

Bulging Recrystallization of

Due to the high density of lath boundary

precipitates, bulging of recrystallized regions into

recovered martensite preferentially occurs in the

longitudinal directions of laths.

Recrystallization of Martensite

J. Mola, B.C. De Cooman, J. Park, Recrystallization behavior of α′ martensite in transformable ferritic stainless steels, in: Proceedings of 7th Eur. Stainl. Steel Conf. Sci. Mark., Como, Italy, 2011.

Fe16Cr0.4Mn0.1Ni0.04C0.04N dual-phase

stainless steel

Rex. annealing conditions:

15 s 830 °C

BF

1 µm

J. Mola, B.C. De Cooman, J. Park, Recrystallization behavior of α′ martensite in transformable ferritic stainless steels, in: Proceedings of 7th Eur. Stainl. Steel Conf. Sci. Mark., Como, Italy, 2011.

Bulging Recrystallization of

Due to the high density of lath boundary precipitates, bulging of recrystallized regions into

recovered martensite preferentially occurs in the longitudinal directions of laths.

Recrystallization of Martensite

Fe16Cr0.4Mn0.1Ni0.04C0.04N dual-phase

stainless steel

Rex. annealing conditions:

15 s 830 °C

BF

Twin

boundary

002 tw-111 tw

-111

-111 tw

-11-1

00-2000

1 µm

Stacking Faults

bccbcc

bcc

Stabilization of austenite in an Fe16Cr0.4Mn0.1Ni0.04C0.04N

transformable stainless steel obtained by Q&P processing

J. Mola, B.C. De Cooman, Quenching and partitioning processing of transformable ferritic stainless steels, Scr. Mater. 65 (2011) 834–837.

BF

BF DF1, ε+α

DF2, ε DF3, α

0.1 m

J. Mola, M. Wendler, A. Weiß, B. Reichel, G. Wolf, B.C. De Cooman, Segregation-Induced Enhancement of Low-Temperature Tensile Ductility in a Cast High-Nitrogen Austenitic Stainless Steel Exhibiting Deformation-Induced α′ Martensite Formation, Metall. Mater. Trans. A. 46 (2015) 1450–1454.

Deformation-Induced Martensite

Z.A.

γ

ത ത ε

α

3ത

ത ത

ത 3ത

ത

BFDF1

DF2

DF3

αʹ-martensite formation at intersections of ε-martensite plates in

Fe14.3Cr5.5Mn5.5Ni0.5Si0.37N0.02C austenitic stainless steel

BF, DF, SAD

εV2

εV1

B.C. De Cooman, P. Gibbs, S. Lee, D.K. Matlock, Transmission Electron Microscopy Analysis of Yielding in Ultrafine-Grained Medium Mn Transformation-Induced Plasticity Steel, Metall. Mater. Trans. A. 44 (2013) 2563–2572.

Deformation-Induced Martensite

1

2

2 1/ nm2 1/ nm

2 1/ nm2 1/ nm

Region 1: γ+ε

Region 2: γ+αʹ+ε

Strain-induced γ ε αʹ transformation

route in an Fe7Mn0.1C medium Mn steel

BF, SAD

α

α

Fe− Cr− Mo−0. C−0.4N

0.2 µm

Fe− Cr− Mo−0. C−0.4N stainless steel after partial transformation to

spontaneous (athermal) α-martensite

Spontaneous Martensite

J. Mola, Considerations in the design of formable austenitic stainless steels based on deformation-induced processes, in Austenitic Stainless Steels - New Aspects, Eds. W. Borek, T. Tański, Z. Brytan, InTechOpen, Typesetting stage.

BF

Fe− Cr− Mo−0. C−0.4N steel after partial transformation to spontaneous (athermal) α-martensite

α

α

0.2 µm

Densely-packed

stacking faults

112 Z.A.

11ത1

3ത1ത12ത20

O

0.2 µm

Planar

faults

Small specimen tilt

Q. Huang, B.C.De Cooman, H. Biermann, J. Mola, Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic–Martensitic Stainless Steels, Metall. Mater. Trans. A. 47 (2016) 1947–1959.

111 planes

Spontaneous Martensite

BF, SAD

50 nm50 nm

Analysis of Precipitates: B2 and σ-Phase

5 1 / nm5 1 / nm

Ferrite + B2-NiAl

BF DF using the marked

B2/σ common spot

BF DF, B2 precipitatesSAED, encircled area

201α Z.A. // 201B2 Z.A. // 23-6σ Z.A.

-1-12α,B2

-112α,B2

020α,B2

-102B2

301σ

010B2

3-20σ

021σ

σ-phase: tetragonal P42/mnm,

a=0.880 nm, c=0.4544 nm

Unpublished

Fe17Cr6Mn

3Ni4Al0.45C

duplex stainless

steel

BF, DF, SAD

100 nm 100 nm