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High manganese steel conference trip maraging steels short version
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Alloy design of nanoprecipitate- hardened high-Mn maraging-TRIP and - TWIP steels D. Ponge, O. Dmitrieva, J. Millán, S. Sandlöbes, P. Choi, A. Kostka, G. Inden, D. Raabe WWW.MPIE.DE [email protected] Dierk Raabe Düsseldorf, Germany
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Alloy design of nanoprecipitate-hardened high-Mn maraging-TRIP and -TWIP steels
Transcript of High manganese steel conference trip maraging steels short version
Alloy design of nanoprecipitate-hardened high-Mn maraging-TRIP and -TWIP steels
D. Ponge, O. Dmitrieva, J. Millán, S. Sandlöbes, P. Choi, A. Kostka, G. Inden, D. Raabe
Dierk Raabe
Düsseldorf, Germany
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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Good combination of strength, ductility, price
Controlled precipitation hardening
Ductile low carbon martensite matrix
Small amount of austenite (TRIP, TWIP)
IntroductionIntroduction
Steel for automotive applications:
Lean Maraging TRIP Steels
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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Low carbon: ductile martensite
Compositions in mass%: classical maraging steelCompositions in mass%: classical maraging steel
Steel C Ni Co Mo Ti Al Mn Fe
Maraging 0.01 18 12 4 1.6 0.15 0.05 Balance
Precipitation hardening
Expensive for automotive applications !
Optimised for very high strength + toughness
We want high strength + ductility
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Low carbon: ductile martensite
Steel C Ni Co Mo Ti Al Mn Fe
Maraging 0.01 18 12 4 1.6 0.15 0.05 Balance
09MnPH 0.01 2 - 1 1.0 0.15 9 Balance
12MnPH 0.01 2 - 1 1.0 0.15 12 Balance
15MnPH 0.01 2 - 1 1.0 0.15 15 Balance
Precipitation Hardenable
Mn (+Ni): austenite (TRIP)
Compositions in mass%: new lean maraging steelsCompositions in mass%: new lean maraging steels
PH
PH
PH
Raabe, Ponge, Dmitrieva, Sander: Adv. Eng. Mat. 11 (2009) 547
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Vacuum induction melting
Annealing
Hot deformation
Quenching
Solution heat treatment
Aging (450°C)
ProcessingProcessing
“Maraging“
Martensite + retained austenite
retained + new austenite
Dmitrieva et al. Acta Mater 59 (2011)
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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0100 101 102 103 104 105
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Time at 450°C (min)
09MnPH09MnPH
12MnPH12MnPH
15MnPH15MnPH
a’a’ gg
Hardness during aging at 450°CHardness during aging at 450°C
12MnPH09MnPH 15MnPH
Dmitrieva et al. Acta Mater 59 (2011)
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precipitates in a`
no precipitates in
12MnPH after aging (48h 450°C)12MnPH after aging (48h 450°C)
nmDtxDiff 302
nmxDiff 2
Dmitrieva et al. Acta Mater 59 (2011)
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Ni-Maragingaged (450°C/48h)
quenched
12MnPHaged (450°C/48h)
quenched
Tensile testsTensile tests
(X3NiCoMoTi18-12-4)
D. Raabe et al. Scripta Materialia 60 (2009) 1141
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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Atom Probe, 12MnPH aged (48h, 450°C) Atom Probe, 12MnPH aged (48h, 450°C)
Ni a‘+particles g (no particles)
Mn enrichment in interface ?
Dmitrieva et al. Acta Mater 59 (2011)
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-5 -4 -3 -2 -1 0 1 2 30
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n (a
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09MnPH450°C/48h
Fe
Ni
Mn
AlTi
matrix particle
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09MnPH450°C/192h
Fe
Ni
Mn
AlTi
matrix particle
09MnPH aging at 450°C, Proxigrams09MnPH aging at 450°C, Proxigrams
Dmitrieva et al. Acta Mater 59 (2011)
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at. % in particles
Ni 39.99Mn 24.70Al 7.02Ti 3.91Fe 23.97
Chemical compositions (09MnPH; 450°C/48h)Chemical compositions (09MnPH; 450°C/48h)
at. % in particles
52.8832.669.285.17
0
47.11
Ni50(Mn,Al,Ti)50possible:
Dmitrieva et al. Acta Mater 59 (2011)
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Aging time at 450°C 48 hours 192 hours
Volume fraction of particles 1.5% 4.3%
Number density of particles (m-3) 3.6x1024 1.9x1024
Mean diameter (nm) 4.7 ± 0.7 6.1 ± 2.2
10 nm
48 hours 192 hours
Iso-conc. surfaces:14 at.% Ni
only Fe and Ni shown
09MnPH aging at 450°C09MnPH aging at 450°C
Dmitrieva et al. Acta Mater 59 (2011)
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PrecipitationsPrecipitations
After aging (48h 450°C) nanosized precipitations in martensite (Ø ~ 5nm; volume fraction ~ 1.5%)
Heusler Alloy (Ni2MnAl)? B2 or L21? Coherent ? Cut by dislocations ?
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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12 wt.% Mn, 0.01 wt.% C, 2 wt.% Ni, 1 wt.% Ti, 0.15 wt.% Al,1 wt.% Mo, 0.06 wt.% Si
TRIP effect(austenite transforms to martensite)
Maraging effect(precipitation hardening in martensite)
D. Raabe, D. Ponge, O. Dmitrieva, B. Sander, Scripta Mater. 60 (2009) 1141D. Raabe, D. Ponge, O. Dmitrieva, B. Sander, Adv. Eng. Mater. 11/7 (2009) 547
Effect of aging on ductilityEffect of aging on ductility
12MnPH
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as-quenched
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-Fe (Martensite)-Fe (Austenite), vol. fraction 15-20%
increase of austenite
fraction during aging
Precipitationhardening
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Effect of aging on ductilityEffect of aging on ductility
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-Fe (Martensite)-Fe (Austenite), vol. fraction 15-20%
increase of austenite
fraction during aging
Precipitationhardening
strain 0%
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?
Effect of aging on ductilityEffect of aging on ductility
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Mn atoms, Ni atomsMn iso-conc: 18 at.%
APT results: Atomic map (12MnPH aged 450°C/48h)
70 million ionsLaser mode (0.4nJ, 54K)
Martensite decorated by precipitations
Austenite
?
?
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OverviewOverview
Introduction
Compositions and processing
Mechanical properties and microstructures
Characterization of precipitations
Conclusions
Formation of new austenite during aging
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Conclusions Conclusions
Martensitic Mn-steels (~0,01wt%C): good ductility
+ controlled amounts of Ni (2 wt%), Al (0.15 wt%), … increase strength during aging by formation of nanosized precipitations without significant reduction of ductility
By controlling the austenite stability (here by Mn) martensite can be refined and ductility can be further increased by retained and reverted austenite (TRIP)
Design of “Lean Maraging TRIP steel“ Precipitation hardening
Austenite (retained + new) Increase ductility
Increase strength
