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An overview of duplex stainless steel for strain induced martensite transformation
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
An overview of duplex stainless steel for strain induced martensite transformation Shivani Koppula ⇑, Pallavi Gugulothu, Akhila Chilikuri, Snigdha Narum, Ram Subbiah, S.K. Singh Mechanical Engineering Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad 500090, India
a r t i c l e
i n f o
Article history: Received 4 January 2020 Accepted 11 January 2020 Available online xxxx Keywords: Strain-induced martensite Strain hardening Duplex stainless steel Microstructure Austenite stability Cold rolling
a b s t r a c t A study of the deformation behavior of lean duplex stainless steels with martensitic transformation caused by strain is presented. The research is dedicated to investigating a duplex stainless steel’s load response. The early grades were chromium, nickel, and molybdenum alloys. Duplex stainless steels, due to their excellent corrosion properties, have many end uses in oil and gas. These were used in subsea applications including flowlines, umbilical tubing, subsea manifolds, lines for water injection and tubing for downhole chemical injection. The strength and ductility of duplex stainless steels is lacking. The distribution of strain-induced martensite (SIM) over a wide range of strain is to be accomplished in order to improve these mechanical properties. The transformation of the martensite induced by the strain is based on optimizing austenite stability. The best combination of strength and ductility, therefore, is achieved. Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
1. Introduction The stainless steel duplex consists of about the same proportions of austenite and ferrite. We are designed to provide increased resistance to corrosion [1]. In the DSS, SIM takes place through a two-step transformation: first some austenite transforms into a sigma martensite and then the latter transforms into an alpha martensite. DSS deformation depends on ferrite and austenite mechanical behavior. The martensitic transformation in DSS [4] can produce a good combination of strength and ductility. Operation of austenite stability is the way to improve strength and ductility. The austenite that can be metastable during plastic deformation transforms through an effect of Transformation Induced Plasticity (TRIP) [2,3].Through preventing plastic localization, the formation of strain-induced martensite (SIM) increases both ultimate tensile strength (UTS) [5] and complete elongation. Depending on the composition of the alloy, SIM formation can take many forms. In order to achieve good results, austenite stability must be accomplished with care. If austenite is excessively unstable, the transformation of SIM begins with small plastic strains and then saturates resulting in high strength but low elongation. The ⇑ Corresponding author. Tel.: +91 8464088815. E-mail address: [email protected] (S. Koppula).
temperature of the heat treatment leading to the duplex microstructure determines the proportion of ferrite and austenite as well as the partitioning of alloying elements between these two phases and thus the consistency of austenite for a given alloy composition. The present study investigated the evolution of microstructure and phase transition in a Linear Duplex Stainless Steel (LDSS), caused by low-voltage cold rolling. The focus of this research was on p-martensite formation for such a degree of formation. 2. Experimental procedure Audrey Lechartier, Nicolas Meyer et al, demonstrated that the first part of this analysis was performed with the following chemical composition Fe-22.12Cr-4.24Ni-1.15Mn-0.28Mo-0.12N-0.021 C (weight percent) on a duplex stainless steel (hereafter called Duplex alloy). This duplex grade corresponds to the 1.4362 grade European standard. Single phase alloys (hereafter referred to as austenitic and ferritic alloys) whose composition corresponds to the Duplex alloy’s austenitic and ferritic phases were formed in the second part. In the Results section, they will be discussed in detail. The third part, four alloy compositions (hereafter referred to as alloys A, B, C and D) were developed using the TCFE6 database Thermo-Calc software to I preserve an equal proportion of austenite and ferrite at
https://doi.org/10.1016/j.matpr.2020.01.307 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
2
S. Koppula et al. / Materials Today: Proceedings xxx (xxxx) xxx
Table 1 Chemical compositions given in weight percent of alloys A, B, C and D. In the undeformed state, ferrite fraction fa is also provided, these values are calculated from Thermocalc’s predicted compositions. Alloy
C
Ni
Cr
N
fa
A B C D
0.02 0.02 0.02 0.02
3.63 4.06 4.28 4.58
23.91 22.85 22.43 22.15
0.02 0.15 0.11 0.07
57.9 49.4 51.9 53.3
Table 2 Chemical ferrite and austenite compositions in Table 10 s four alloys in their undeformed state. Measurements were performed by micro-sample analysis and are given in percentage wt. For the austenite process, Md30 temperatures calculated using the Nohara formula are given as an indication of its stability during strain. Alloy
Phase
Ni
A B C D
ac ac ac ac
2.8 2.8 3.0 3.1
Cr 4.4 4.8 5.3 5.6
1000° C under determined equilibrium and (ii) exhibit different degrees of austenite stability with respect to room temperature plastic deformation. The austenite stability was determined as a design guide based on the Md30 temperature measured by the empirical formula Nohara [6] applied at 1000° C to the calculated austenite compositions. This value is the temperature at which a true strain of 0.3 [7] converted 50 percent of austenite into martensite. A high temperature of Md30 corresponds to unstable austenite and a low temperature of Md30 corresponds to stable austenite. X-ray fluorescence spectrometry was used to determine chemical compositions, except for carbon and nitrogen tested with a LECO apparatus through combustion and gas fusion analysis. Table 1 shows the predicted ferrite fractions and calculated chemical composition of the four investigated alloys, with the predicted degree of austenitic phase instability from alloy A to D as shown in the Md30 values in Table 2, which also indicates the chemical compositions of ferrite and austenite in the four steels. One can notice that alloy C is close to the Duplex alloy’s chemical composition. The four alloys A to D were casted to 25 kg ingots using a process
25.3 25.6 25.6 25.1
N 22.9 21.7 21.1 20.5
0.02 0.02 0.02 0.02
Md30 (°C) 0.39 0.21 0.16 0.12
NA NA NA NA
119 13 3 24
of vacuum induction melting. These ingots were forged hot and then rolled hot at 1180° C to a thickness of 6 mm. Immediately followed by a solution annealing procedure of 2 h at 1000° C, water quenching was applied to prevent harmful precipitation during cooling of the brittle p-phase. Eventually, while examining the impact of pre-deformation, a cold rolling procedure of 10% and a relative thickness reduction of 20% was performed. G.G.B Maria, D.G Rodrigues et al, demonstrated that this study also used a 4.0 mm nominal thickness LDSS hot-rolled unit. The chemical composition is 0.011 percent C, 0.453 percent Cu, 0.275 percent Mo, 0.20 percent Si, 4.2 percent Ni, and 1.45 percent Mn. The LDSS was cold-rolled with a reduction in thickness of 4, 12, 17 and 22 percent. During the longitudinal portion, the microstructure was characterized by the technique of electron backscatter diffraction (EBSD). Using the TSL-EDAX analysis software, the phase size used was 53 nm and the data acquired were analyzed. The X-ray diffraction scan was obtained in a PANalytical Empyrean diffractometer using CuKa radiation, phase size of 0.005o per 1 s, and angular interval 2 of 10–100. TEM samples were thinned
Fig. 1. TEM micrograph after 22% cold rolling. a) BF micrograph h1 1 0ic//<0001 > e b) SAED; c) DP of the parent phase; d) DF of the point 3; e) a0 -martensite f) CBED DP of the a0 -martensite w.r.t Graziele Gianini Braga Maria et al.
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
S. Koppula et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
Fig. 2. Graphs of (a) Yield stress and (b) UTS as a function of fracture strain, for the four model alloys A to D and the three levels of pre-deformation, and for the Duplex alloy in the undeformed state w.r.t Audrey Lechartier et al.
mechanically to 50 lm, followed by electro-polishing using HClO4: C2H4O2 = 1:9 solution with a potential of 50 V at 17 °C [8]. 3. Results and discussions
stainless steels showing a transformation-induced martensitic transformation, their relationship with stress-strain curves, and the effect on mechanical behavior of alloy composition and pre-deformation. It is possible to draw the major conclusions as follows. - In these alloys, a strain-induced martensite transition occurs by a two-step process involving the formation of p-martensite followed by the formation of a’-martensite at the intersection of p-martensite bands. - The kinetics of strain-induced transformation in duplex alloy are similar but slower than in an austenitic alloy with the same composition as the duplex alloy’s austenitic phase. - A rather simple mechanical model was able to capture both the stress-strain behavior of austenite and duplex alloys from the experimentally determined martensite fractions, using only one set of constitutive laws for the three materials involved: austenite, ferrite and martensite.
The figure shows a 22 percent reduction in thickness of the LDSS TEM micrographs. A thick plate-type can be observed in the micrograph from the Figure(a). The region’s selected area diffraction pattern shown by number one (Figure(b)) indicates the p-martensite inside the austenite kernel, as shown by the diffraction pattern (DP), Illustration(c). In addition, the martensite thick plate as shown in Figure(e) was also defined in an austenite grain close to the p-martensite (indicated by number 3) and grain boundaries. In the region identified by the red circle, the DP (Figure (f)) was carried out as shown in Fig. 1 & Fig. 2. After a reduction in thickness of 22 percent, p-martensite was identified in austenite. The study of SADP was shown in Fig. (B) discloses the Shoji–Nishiyama orientation relationship of h1 1 0ip/<2110 > p. Deficiencies in the structure produced by overlapping the deformation-induced stacking faults of the p{1 1 1} axis, such as shear bands and twins, function as embryos for the creation of p and a’-martensite. When intrinsic stacking faults overlap regularly on each second{1 1 1} plane [10], the p-martensite is formed. Furthermore, the a’-martensite is created in the intersections of p-martensite [9]. Rémy and Pineau [11] recorded that between 10 and 15 mJ/m2 martensite type of SFE. According to Ghosh et al. [12], the p-martensite develops a low strain and is transformed by that deformation. Choi and so on. Al [13] reported p-martensite formation in Mn-N DSS shear bands for deformation ranges between 5% and 10%. Zhang and Hu [14] reported that improved plasticity is achieved through the gradual transformation in LDSS. In this sample, because of this low amount, the p-martensite was not detected in XRD analysis. Stage and procedure detection cap. Meanwhile, the growth of the a-phase with the increase of the deformation signaled the transition of the a-alpha.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
4. Conclusion
References
- The LDSS showed p and a’-martensite developed in shear bands and near the grain boundaries for low deformation levels, but the predominant phase was the a’marternsite. The transformation of the process took place because of the low SFE value of 19 mJ/m2. The direction of the martensite relationship h1 1 0ip/<2110 > p.This research has systematically investigated the mechanisms of plastic deformation in duplex
Changing the alloy chemistry by playing the Ni/N ratio or the thermomechanical direction by changing the pre-deformation stage is an efficient way to adjust the DSS yield strength/ultimate tensile strength/elongation compromise. Due to the quality of other alloy elements of our steels, the optimum range of Ni/N ratio lies between alloys B and C. - The stability of austenites is the key parameter for plastic behavior control. The strain hardening rate can remain slightly above the true stress value up to large strains when properly adjusted, thus promoting a good combination of ultimate tensile strength and elongation. Declaration of competing Interest
[1] Audrey Lechartier, Nicolas Meyer, Rafael Estevez, Marc Mantel, Guilhem Martin, Guillaume Parry, Muriel Veron, Alexis Deschamps, Deformation behavior of lean duplex stainless steels with strain induced martensitic transformation: Role of deformation mechanisms, alloy chemistry and predeformation, Materialia 5 (100190) (2019) 101–113. [2] L. Remy, A. Pineau, Twinning and strain-induced F.C.C. ? H.C.P. transformation in the Fe-Mn-Cr-C system, Mater. Sci. Eng. 28 (1977) 99–107. [3] M. Moallemi, A. Zarei-Hanzaki, M. Eskandari, A. Burrows, H. Alimadadi, Comprehensive deformation analysis of a newly designed Ni-Free Duplex
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
4
[4] [5]
[6]
[7] [8] [9]
S. Koppula et al. / Materials Today: Proceedings xxx (xxxx) xxx stainless steel with enhanced plasticity by optimizing austenite stability, Metall. Mater. Trans. Phys. Metall. Mater. Sci. 48A (2017) 3675–3691. Y.-S. Jung, Y.-K. Lee, Effect of pre-deformation on the tensile properties of a metastable austenitic steel, Scr. Mater. 59 (2008) 47–50. K. Spencer, J.D. Embury, K.T. Conlon, M. Véron, Y. Bréchet, Strengthening via the formation of strain-induced martensite in stainless steels, Mater. Sci. Eng. A. 387–389 (2004) 873–881. K. Nohara, Y. One, N. Ohashi, Composition and grain size dependencies of strain-induced martensitic transformation in metastable austenitic stainless steels, J. Iron Steel Inst. Jpn. 63 (1977) 212–222. T.J. Angel, Formation of martensite in austenitic stainless steels, J. Iron Steel Inst. 177 (1954) 165–174. G.G.B. Maria, D.G. Rodrigues, E.T.F. Freitas, D.B. Santos, e-martensite formation for low strains in a lean duplex stainless steel, Mater. Lett. (2018) 142–153. M. Breda, K. Brunelli, F. Grazzi, A. Scherillo, I. Calliari, Effects of Cold Rolling and StrainInduced Martensite Formation in a SAF 2205 Duplex Stainless Steel, Metall. Mater. Trans. A. 46 (2015) 577–586.
[10] J. Talonen, H. Hänninen, Formation of shear bands and strain-induced martensite during plastic deformation of metastable austenitic stainless steels, Acta Mater. 55 (2007) 6108–6118. [11] S.K. Ghosh, P. Mallick, P.P. Chattopadhyay, Effect of reversion of strain induced martensite on microstructure and mechanical properties in an austenitic stainless steel, J. Mater. Sci. 46 (2011) 3480–3487. [12] J.Y. Choi, J.H. Ji, S.W. Hwang, K.T. Park, TRIP aided deformation of a near-Nifree, Mn-N bearing duplex stainless steel, Mater. Sci. Eng. A. 535 (2012) 32– 39. [13] W. Zhang, J. Hu, Effect of annealing temperature on transformation induced plasticity effect of a lean duplex stainless steel, Mater. Charact. 79 (2013) 37– 42. [14] W. Woo, J. Kim, E.-Y. Kim, S.-H. Choi, V. Em, D.S. Hussey, Multi-scale analyses of constituent phases in a trip-assisted duplex stainless steel by electron backscatter diffraction, in situ neutron diffraction, and energy selective neutron imaging, Scr. Mater. 158 (2019) 105–109.
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
An overview of duplex stainless steel for strain induced martensite transformation Shivani Koppula ⇑, Pallavi Gugulothu, Akhila Chilikuri, Snigdha Narum, Ram Subbiah, S.K. Singh Mechanical Engineering Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad 500090, India
a r t i c l e
i n f o
Article history: Received 4 January 2020 Accepted 11 January 2020 Available online xxxx Keywords: Strain-induced martensite Strain hardening Duplex stainless steel Microstructure Austenite stability Cold rolling
a b s t r a c t A study of the deformation behavior of lean duplex stainless steels with martensitic transformation caused by strain is presented. The research is dedicated to investigating a duplex stainless steel’s load response. The early grades were chromium, nickel, and molybdenum alloys. Duplex stainless steels, due to their excellent corrosion properties, have many end uses in oil and gas. These were used in subsea applications including flowlines, umbilical tubing, subsea manifolds, lines for water injection and tubing for downhole chemical injection. The strength and ductility of duplex stainless steels is lacking. The distribution of strain-induced martensite (SIM) over a wide range of strain is to be accomplished in order to improve these mechanical properties. The transformation of the martensite induced by the strain is based on optimizing austenite stability. The best combination of strength and ductility, therefore, is achieved. Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
1. Introduction The stainless steel duplex consists of about the same proportions of austenite and ferrite. We are designed to provide increased resistance to corrosion [1]. In the DSS, SIM takes place through a two-step transformation: first some austenite transforms into a sigma martensite and then the latter transforms into an alpha martensite. DSS deformation depends on ferrite and austenite mechanical behavior. The martensitic transformation in DSS [4] can produce a good combination of strength and ductility. Operation of austenite stability is the way to improve strength and ductility. The austenite that can be metastable during plastic deformation transforms through an effect of Transformation Induced Plasticity (TRIP) [2,3].Through preventing plastic localization, the formation of strain-induced martensite (SIM) increases both ultimate tensile strength (UTS) [5] and complete elongation. Depending on the composition of the alloy, SIM formation can take many forms. In order to achieve good results, austenite stability must be accomplished with care. If austenite is excessively unstable, the transformation of SIM begins with small plastic strains and then saturates resulting in high strength but low elongation. The ⇑ Corresponding author. Tel.: +91 8464088815. E-mail address: [email protected] (S. Koppula).
temperature of the heat treatment leading to the duplex microstructure determines the proportion of ferrite and austenite as well as the partitioning of alloying elements between these two phases and thus the consistency of austenite for a given alloy composition. The present study investigated the evolution of microstructure and phase transition in a Linear Duplex Stainless Steel (LDSS), caused by low-voltage cold rolling. The focus of this research was on p-martensite formation for such a degree of formation. 2. Experimental procedure Audrey Lechartier, Nicolas Meyer et al, demonstrated that the first part of this analysis was performed with the following chemical composition Fe-22.12Cr-4.24Ni-1.15Mn-0.28Mo-0.12N-0.021 C (weight percent) on a duplex stainless steel (hereafter called Duplex alloy). This duplex grade corresponds to the 1.4362 grade European standard. Single phase alloys (hereafter referred to as austenitic and ferritic alloys) whose composition corresponds to the Duplex alloy’s austenitic and ferritic phases were formed in the second part. In the Results section, they will be discussed in detail. The third part, four alloy compositions (hereafter referred to as alloys A, B, C and D) were developed using the TCFE6 database Thermo-Calc software to I preserve an equal proportion of austenite and ferrite at
https://doi.org/10.1016/j.matpr.2020.01.307 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
2
S. Koppula et al. / Materials Today: Proceedings xxx (xxxx) xxx
Table 1 Chemical compositions given in weight percent of alloys A, B, C and D. In the undeformed state, ferrite fraction fa is also provided, these values are calculated from Thermocalc’s predicted compositions. Alloy
C
Ni
Cr
N
fa
A B C D
0.02 0.02 0.02 0.02
3.63 4.06 4.28 4.58
23.91 22.85 22.43 22.15
0.02 0.15 0.11 0.07
57.9 49.4 51.9 53.3
Table 2 Chemical ferrite and austenite compositions in Table 10 s four alloys in their undeformed state. Measurements were performed by micro-sample analysis and are given in percentage wt. For the austenite process, Md30 temperatures calculated using the Nohara formula are given as an indication of its stability during strain. Alloy
Phase
Ni
A B C D
ac ac ac ac
2.8 2.8 3.0 3.1
Cr 4.4 4.8 5.3 5.6
1000° C under determined equilibrium and (ii) exhibit different degrees of austenite stability with respect to room temperature plastic deformation. The austenite stability was determined as a design guide based on the Md30 temperature measured by the empirical formula Nohara [6] applied at 1000° C to the calculated austenite compositions. This value is the temperature at which a true strain of 0.3 [7] converted 50 percent of austenite into martensite. A high temperature of Md30 corresponds to unstable austenite and a low temperature of Md30 corresponds to stable austenite. X-ray fluorescence spectrometry was used to determine chemical compositions, except for carbon and nitrogen tested with a LECO apparatus through combustion and gas fusion analysis. Table 1 shows the predicted ferrite fractions and calculated chemical composition of the four investigated alloys, with the predicted degree of austenitic phase instability from alloy A to D as shown in the Md30 values in Table 2, which also indicates the chemical compositions of ferrite and austenite in the four steels. One can notice that alloy C is close to the Duplex alloy’s chemical composition. The four alloys A to D were casted to 25 kg ingots using a process
25.3 25.6 25.6 25.1
N 22.9 21.7 21.1 20.5
0.02 0.02 0.02 0.02
Md30 (°C) 0.39 0.21 0.16 0.12
NA NA NA NA
119 13 3 24
of vacuum induction melting. These ingots were forged hot and then rolled hot at 1180° C to a thickness of 6 mm. Immediately followed by a solution annealing procedure of 2 h at 1000° C, water quenching was applied to prevent harmful precipitation during cooling of the brittle p-phase. Eventually, while examining the impact of pre-deformation, a cold rolling procedure of 10% and a relative thickness reduction of 20% was performed. G.G.B Maria, D.G Rodrigues et al, demonstrated that this study also used a 4.0 mm nominal thickness LDSS hot-rolled unit. The chemical composition is 0.011 percent C, 0.453 percent Cu, 0.275 percent Mo, 0.20 percent Si, 4.2 percent Ni, and 1.45 percent Mn. The LDSS was cold-rolled with a reduction in thickness of 4, 12, 17 and 22 percent. During the longitudinal portion, the microstructure was characterized by the technique of electron backscatter diffraction (EBSD). Using the TSL-EDAX analysis software, the phase size used was 53 nm and the data acquired were analyzed. The X-ray diffraction scan was obtained in a PANalytical Empyrean diffractometer using CuKa radiation, phase size of 0.005o per 1 s, and angular interval 2 of 10–100. TEM samples were thinned
Fig. 1. TEM micrograph after 22% cold rolling. a) BF micrograph h1 1 0ic//<0001 > e b) SAED; c) DP of the parent phase; d) DF of the point 3; e) a0 -martensite f) CBED DP of the a0 -martensite w.r.t Graziele Gianini Braga Maria et al.
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
S. Koppula et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
Fig. 2. Graphs of (a) Yield stress and (b) UTS as a function of fracture strain, for the four model alloys A to D and the three levels of pre-deformation, and for the Duplex alloy in the undeformed state w.r.t Audrey Lechartier et al.
mechanically to 50 lm, followed by electro-polishing using HClO4: C2H4O2 = 1:9 solution with a potential of 50 V at 17 °C [8]. 3. Results and discussions
stainless steels showing a transformation-induced martensitic transformation, their relationship with stress-strain curves, and the effect on mechanical behavior of alloy composition and pre-deformation. It is possible to draw the major conclusions as follows. - In these alloys, a strain-induced martensite transition occurs by a two-step process involving the formation of p-martensite followed by the formation of a’-martensite at the intersection of p-martensite bands. - The kinetics of strain-induced transformation in duplex alloy are similar but slower than in an austenitic alloy with the same composition as the duplex alloy’s austenitic phase. - A rather simple mechanical model was able to capture both the stress-strain behavior of austenite and duplex alloys from the experimentally determined martensite fractions, using only one set of constitutive laws for the three materials involved: austenite, ferrite and martensite.
The figure shows a 22 percent reduction in thickness of the LDSS TEM micrographs. A thick plate-type can be observed in the micrograph from the Figure(a). The region’s selected area diffraction pattern shown by number one (Figure(b)) indicates the p-martensite inside the austenite kernel, as shown by the diffraction pattern (DP), Illustration(c). In addition, the martensite thick plate as shown in Figure(e) was also defined in an austenite grain close to the p-martensite (indicated by number 3) and grain boundaries. In the region identified by the red circle, the DP (Figure (f)) was carried out as shown in Fig. 1 & Fig. 2. After a reduction in thickness of 22 percent, p-martensite was identified in austenite. The study of SADP was shown in Fig. (B) discloses the Shoji–Nishiyama orientation relationship of h1 1 0ip/<2110 > p. Deficiencies in the structure produced by overlapping the deformation-induced stacking faults of the p{1 1 1} axis, such as shear bands and twins, function as embryos for the creation of p and a’-martensite. When intrinsic stacking faults overlap regularly on each second{1 1 1} plane [10], the p-martensite is formed. Furthermore, the a’-martensite is created in the intersections of p-martensite [9]. Rémy and Pineau [11] recorded that between 10 and 15 mJ/m2 martensite type of SFE. According to Ghosh et al. [12], the p-martensite develops a low strain and is transformed by that deformation. Choi and so on. Al [13] reported p-martensite formation in Mn-N DSS shear bands for deformation ranges between 5% and 10%. Zhang and Hu [14] reported that improved plasticity is achieved through the gradual transformation in LDSS. In this sample, because of this low amount, the p-martensite was not detected in XRD analysis. Stage and procedure detection cap. Meanwhile, the growth of the a-phase with the increase of the deformation signaled the transition of the a-alpha.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
4. Conclusion
References
- The LDSS showed p and a’-martensite developed in shear bands and near the grain boundaries for low deformation levels, but the predominant phase was the a’marternsite. The transformation of the process took place because of the low SFE value of 19 mJ/m2. The direction of the martensite relationship h1 1 0ip/<2110 > p.This research has systematically investigated the mechanisms of plastic deformation in duplex
Changing the alloy chemistry by playing the Ni/N ratio or the thermomechanical direction by changing the pre-deformation stage is an efficient way to adjust the DSS yield strength/ultimate tensile strength/elongation compromise. Due to the quality of other alloy elements of our steels, the optimum range of Ni/N ratio lies between alloys B and C. - The stability of austenites is the key parameter for plastic behavior control. The strain hardening rate can remain slightly above the true stress value up to large strains when properly adjusted, thus promoting a good combination of ultimate tensile strength and elongation. Declaration of competing Interest
[1] Audrey Lechartier, Nicolas Meyer, Rafael Estevez, Marc Mantel, Guilhem Martin, Guillaume Parry, Muriel Veron, Alexis Deschamps, Deformation behavior of lean duplex stainless steels with strain induced martensitic transformation: Role of deformation mechanisms, alloy chemistry and predeformation, Materialia 5 (100190) (2019) 101–113. [2] L. Remy, A. Pineau, Twinning and strain-induced F.C.C. ? H.C.P. transformation in the Fe-Mn-Cr-C system, Mater. Sci. Eng. 28 (1977) 99–107. [3] M. Moallemi, A. Zarei-Hanzaki, M. Eskandari, A. Burrows, H. Alimadadi, Comprehensive deformation analysis of a newly designed Ni-Free Duplex
Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307
4
[4] [5]
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Please cite this article as: S. Koppula, P. Gugulothu, A. Chilikuri et al., An overview of duplex stainless steel for strain induced martensite transformation, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.307