Download - Graduate Seminar I
![Page 1: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/1.jpg)
Graduate Seminar I
Compositionally Graded High Manganese Steels
by
Morteza Ghasri
Supervisor: Prof. McDermid
Nov. 18, 2011
![Page 2: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/2.jpg)
2
Presentation OutlineIntroduction
Literature Review
Project Objectives
Experimental Method
Preliminary Results
Plan for Future Work
![Page 3: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/3.jpg)
3
Introduction
Typical mechanical properties of several classes of steelsW. Bleck: International Conference on TRIP-Aided High Strength Ferrous Alloys, Ghent,
Belgium 2002, p. 13-23
![Page 4: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/4.jpg)
4
History of high Mn steels
Hadfield steels were invented in 1882.They had 13 wt. % Mn and 1.2 wt. % C.
● New class of modern high Mn steels contain 18-30 wt. % Mn, 0-0.7 wt. % C, and up to 1-2 wt. % (Al, Si) Sir Robert Hadfield
1858-1940
![Page 5: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/5.jpg)
5
High Mn steels can be divided into:
Twinning Induced Plasticity (TWIP)
Transformation Induced Plasticity (TRIP)
Literature Review
![Page 6: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/6.jpg)
6
Stacking fault formation
1. Dissociation of a perfect dislocation
2. Equilibrium between two partial dislocations
d: the equilibrium separation between partials μ: shear modulusb: the magnitude of the Burger’s vector γ: stacking fault energy
Stacking Fault Energy
]211[6
]112[6
]011[2
aaa
4
2bd
![Page 7: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/7.jpg)
7
SFE dependence of deformation products
Deformation structures of Fe-20Mn-4Cr-0.5C as a function of both temperature and SFE
L. Remy et al., Materials science and Engineering, Vol. 28, pp. 99-107, 1977
Deformation structures of different alloys observed near room temperature as a function of SFE
L. Remy et al., Materials Science and Engineering, Vol. 26, pp. 123-132, 1976
![Page 8: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/8.jpg)
8
SFE dependence of deformation products (cont’d)
The calculated iso-SFE lines in the carbon/manganese (wt.%) map at 300K
S. Allain et al., Materials Science and Engineering A, Vol. 387-389, pp. 158-162, 2004
![Page 9: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/9.jpg)
9
SFE dependence of deformation products (cont’d)
The calculated iso-SFE contours in Fe-Mn-C system at 298 K with martensite boundaries
J. Nakano et al., CALPHAD, Vol. 34, pp. 167-175, 2010.
![Page 10: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/10.jpg)
10
Evolution of ε-martensite phase volume fraction with plastic strain in Fe-30Mn-0C alloy
Fe-30Mn-0C alloy
Xin Liang, Master’s thesis, McMaster University, 2008.
Minor ε-martensite for εT<0.3
![Page 11: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/11.jpg)
11
Fe-30Mn-0C alloy
Dislocation cell structure with no significant transformation products
Indicates that dislocation glide is the dominant deformation mechanism at 298 K
BF image of well-developed cell structures in one grain
Xin Liang, Master’s thesis, McMaster University, 2008.
![Page 12: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/12.jpg)
12
Tensile behavior of Fe-22Mn alloys with different carbon content.
Eileen Yang, Master’s thesis, McMaster University, 2010
Fe-22Mn-C alloys
Eileen Yang decarburized an Fe-22Mn-0.6C alloy to obtain homogenous 0.2 C and 0.4 C alloy.
Mechanical properties varied significantly with alloy carbon content.
![Page 13: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/13.jpg)
13
Fe-22Mn-C alloys
Evolution of ε-martensite phase volume fraction with plastic strain for all alloys
Eileen Yang, Master’s thesis, McMaster University, 2010
0.6 C alloy………TWIP
0.2 C alloy……….TRIP
![Page 14: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/14.jpg)
14
Strain Hardening
Isotropic Strain Hardening
• The mechanical response is symmetric after a change of strain path from pure tension to pure compression and vice versa.
• The Kocks-Mecking model considers only this type of strain hardening. Kinematic Strain Hardening
• The mechanical behaviour becomes asymmetric after a change of strain path from pure tension to pure compression.
• This occurs in addition to isotropic strain hardening.
• Kinematic strain hardening has a significant contribution to overall hardening in high Mn steels.
![Page 15: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/15.jpg)
15
Project Objectives
1. Producing compositionally graded high manganese steels.
2. Microstructural evolution and mechanical properties of produced alloys.
3. Modeling of mechanical properties
The rule-of-mixture approximations Continuum finite element formulation of the constitutive phases
![Page 16: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/16.jpg)
16
Fe-30Mn-0.6C
Fe-30Mn-0C
Fe-30Mn-0.6C
Fe-30Mn-0C
Fe-30Mn-0.6C
Fe-30Mn-0C
1. Fe-30Mn-0C alloy will be carburized to obtain carbon gradient from 0 wt. % at the core to 0.6 wt. % at the surface.
2. Fe-30Mn-0.6C alloy will be decarburized to obtain carbon gradient from 0 wt. % at the surface to 0.6 wt. % at the core.
Experimental alloys
![Page 17: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/17.jpg)
17
Experimental Alloys (cont’d)
3. Fe-22Mn-0.6C alloy will be decarburized to obtain carbon gradient from 0 wt. % at the surface to 0.6 wt. % at the core. Fe-22Mn-0.6C
Fe-22Mn-0C
Fe-22Mn-0C
![Page 18: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/18.jpg)
18
Experimental Method
Carburizing and Decarburizing Heat Treatment
• A gas mixture of CO/CO2 was used for carburizing the Fe-30Mn-0C alloy. The gas mixture was then replaced by CH4/H2.
• Fe-22Mn-0.6C alloy was decarburized by CO/CO2.
•The experiments were carried out at 1000 and 1100 °C.Mico-Hardness Measurements
• To evaluate the distribution of carbon within the cross section of carburized and decarburized samples.
![Page 19: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/19.jpg)
19
Characterization Techniques
• Carbon and sulfur combustion analysis
• Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS)
• Electron BackScattered Diffraction (EBSD)
• X-Ray Diffraction (XRD)
• Transmission Electron Microscopy (TEM)
Experimental Method (cont’d)
![Page 20: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/20.jpg)
20
Preliminary Results
1. Carburization of Fe-30Mn-0C alloy
Illustration of micro-hardness profile after carburizing at 1100°C under a CO/CO2 ratio of 30 for 4 and 7 hours.
The calculated CO/CO2 ratio required for carburization was 16.
Significant increase in hardness was only observed at 50 µm or less from the surface.
![Page 21: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/21.jpg)
21
Fe
Mn O
EDS map of cross section of Fe-30Mn-0C alloy after carburizing for 7 h at 1100 °C.
![Page 22: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/22.jpg)
22
XRD pattern of 7 h-carburized sample.
![Page 23: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/23.jpg)
23
Thermodynamic Aspects
22 21OCOCO TG 81.862824001
2121 )]exp()[(])[( 22
2 RTG
PP
KPP
PCO
CO
CO
COO
The oxygen partial pressure in the furnace is calculated to be 4.24×10-16 atm when T=1373 K and CO/CO2 =30.
MnOOMn 221 TG 32.763889003
2323 )]exp(.[).(
2
RTGaKaP MnMnO
The oxygen partial pressure required for manganese oxidation of Fe-30Mn-0C is calculated to be 3.34×10-21 atm.
![Page 24: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/24.jpg)
24
2. Carburization of Fe-30Mn-0C alloy using CH4/H2
CO/CO2 gas mixture was replaced by CH4/H2 mixture to prevent MnO formation.
Methane decomposition leads to carburization
Oxygen as impurity in methane leads to MnO formation.
Ti wire was used to lower the oxygen potential.
24 2HCCH
![Page 25: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/25.jpg)
25
3. Decarburization of Fe-22Mn-0.6C alloy
Illustration of micro-hardness profile after decarburizing at 1000°C under CO/CO2 ratios of 6 and 1 for 4 hours.
The high amount of hardness at 50 μm below the surface is attributed to MnO formation.
The carbon content of decarburized samples decreased from 0.40 wt. % to 0.20 wt. % when the CO/CO2 decreased from 6 to 1.
0 200 400 600 800 1000 1200 1400 16000
50
100
150
200
250
300
CO/CO2 ratio=6
Depth (µm)
Mic
roha
rdne
ss (H
V)
0 200 400 600 800 1000 1200 1400 16000
50
100
150
200
250
300
CO/CO2 ratio=1
Depth (µm)
Mic
roha
rdne
ss (H
V)
![Page 26: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/26.jpg)
26
Thermodynamic Aspects
The oxygen partial pressure in the furnace is calculated to be 2.17×10-16 atm when T=1273 K and CO/CO2 = 6.
The oxygen partial pressure required for manganese oxidation of Fe-22Mn-0.6C is calculated to be 2.36×10-23 atm.
![Page 27: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/27.jpg)
27
Plan for Future Work
![Page 28: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/28.jpg)
28
Conclusion
MnO layer on high Mn steels prevents carbon diffusion into the sample, but it has no significant effect on decarburization.
![Page 29: Graduate Seminar I](https://reader036.vdocument.in/reader036/viewer/2022070423/568166e4550346895ddb1d19/html5/thumbnails/29.jpg)
29
Acknowledgement
• Prof. McDermid
• Dr. Zurob
• Doug Culley
• Chris Butcher
• Tom Zhou
• Research Group Fellows