Microstructures and Properties of Martensitic Materials

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (15 November 2018) | Viewed by 38494

Special Issue Editor

Swiss Federal Institute of Technology EPFL, Lausanne, Lausanne, Switzerland
Interests: metallurgy; EBSD; TEM; crystallography; martensitic transformations; twinning; variants; group theory
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Special Issue Information

Dear Colleagues,

Martensite was evidenced in steels at the end of the 19th century. It is a particular complex microstructure made of isolated or intricate laths or plates built by the collective displacements of atoms during a diffusionless phase transformation. It can be observed in many materials, such as cobalt, titanium, zirconium, shape memory alloys, in some gold alloys, brasses and other copper alloys, and in some ceramics and polymers. Their extraordinary mechanical and physical properties, used in many industrial domains, explain why these materials have been extensively studied for the last century. The phenomenological theory, developed in the 1950s, filled a gap in our understanding regarding their crystallography, morphologies and mechanical properties, but many questions remain unsolved or prone to controversies. The way that atoms move, the correlation with phonon softening, the effect of chemical composition, the link with other types of microstructures (for example, Widmanstätten ferrite, bainite, or massive phases), and the role of the dislocations/disclinations, all these issues are still open to discussions and debates. The improvements in the characterization techniques, such as aberration-corrected transmission electron microscopy, fast and high-resolution electron backscatter diffraction, atom probe, ultrafast X-ray and neutron diffraction, and the new possibilities offered by molecular dynamics simulations and phase field models, have helped us to get more results, but we still lack a deep and global understanding on the way martensitic materials form and react.

All the contributions are welcome in this Special Issue “Microstructures and Properties of Martensitic Materials”, including critical and constructive reviews, new surprising experimental results, even if not yet fully understood and interpreted, and new theoretical models, even if they are unconventional or imply shifting some paradigms.

Dr. Cyril Cayron
Guest Editor

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Keywords

  • Martensitic transformations
  • Microstructures
  • Twins and variants
  • Characterization
  • Properties
  • Models

Published Papers (10 papers)

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Editorial

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3 pages, 156 KiB  
Editorial
Microstructures and Properties of Martensitic Materials
by Cyril Cayron
Crystals 2019, 9(3), 152; https://doi.org/10.3390/cryst9030152 - 14 Mar 2019
Viewed by 2048
Abstract
Martensite, initially named in honor of Adolph Martens and his pioneering work in metallography and microstructures at the end of the 19th century, has now a far broader meaning than previously used [...] Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)

Research

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13 pages, 4654 KiB  
Article
Effect of C on the Martensitic Transformation in Fe-C Alloys in the Presence of Pre-Existing Defects: A Molecular Dynamics Study
by Shivraj Karewar, Jilt Sietsma and Maria J. Santofimia
Crystals 2019, 9(2), 99; https://doi.org/10.3390/cryst9020099 - 15 Feb 2019
Cited by 18 | Viewed by 4389
Abstract
Molecular dynamics simulations are used to investigate the atomic effects of carbon (C) addition in Fe on the martensitic phase transformation in the presence of pre-existing defects such as stacking faults and twin boundaries. The pre-existing defect structures in Fe-C alloys have the [...] Read more.
Molecular dynamics simulations are used to investigate the atomic effects of carbon (C) addition in Fe on the martensitic phase transformation in the presence of pre-existing defects such as stacking faults and twin boundaries. The pre-existing defect structures in Fe-C alloys have the same effect on the atomistic mechanisms of martensitic transformation as in pure Fe. However, C addition decreases the martensitic transformation temperature. This effect is captured by characterizing three parameters at the atomic level: atomic shear stresses, atomic energy, and total energy as a function of temperature for face-centered-cubic (fcc) and body-centered-cubic (bcc) phases. The thermodynamic effect of fcc phase stabilization by C addition is revealed by the atomic energy at a particular temperature and total energy as a function of temperature. The barrier for fcc-to-bcc transformation is revealed by analysis of atomic shear stresses. The analysis indicates that addition of C increases the atomic shear stresses for atomic displacements during martensitic transformation, which in turn decreases the martensitic transformation temperature. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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10 pages, 5773 KiB  
Article
The Mechanism of High-Strength Quenching-Partitioning-Tempering Martensitic Steel at Elevated Temperatures
by Ke Zhang, Maoyuan Zhu, Bitong Lan, Ping Liu, Wei Li and Yonghua Rong
Crystals 2019, 9(2), 94; https://doi.org/10.3390/cryst9020094 - 13 Feb 2019
Cited by 13 | Viewed by 2803
Abstract
High-strength medium-carbon martensitic steel was heat treated through a quenching-partitioning-tempering (Q-P-T) treatment. Both the mechanism for improved ductility and the high temperature stability of austenite were investigated. The Q-P-T martensitic steel showed good products of strength and elongation (PSE) at various deformation temperatures [...] Read more.
High-strength medium-carbon martensitic steel was heat treated through a quenching-partitioning-tempering (Q-P-T) treatment. Both the mechanism for improved ductility and the high temperature stability of austenite were investigated. The Q-P-T martensitic steel showed good products of strength and elongation (PSE) at various deformation temperatures ranging within 25–350 °C. The optimum PSE value (>57,738 MPa%) was achieved at 200 °C. The microstructure of the Q-P-T steel is constituted of laths martensite with dislocations, retained austenite located within lath martensite and small niobium carbides (NbC), and/or transitional ε-carbides that precipitated in the lath martensite. The good ductility can be mainly attributed to the laminar-like austenite that remained within the lath-martensite. The austenite can effectively enhance ductility through the effect of dislocation absorption by the retained austenite and through transformation-induced plasticity. The relationship between the microstructures and mechanical properties was investigated at high deformation temperatures. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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10 pages, 46043 KiB  
Article
Microstructure of Plasma Nitrided AISI420 Martensitic Stainless Steel at 673 K
by Tatsuhiko Aizawa, Tomoaki Yoshino, Kazuo Morikawa and Sho-Ichiro Yoshihara
Crystals 2019, 9(2), 60; https://doi.org/10.3390/cryst9020060 - 24 Jan 2019
Cited by 12 | Viewed by 2858
Abstract
Martensitic stainless steel type AISI420 was plasma nitrided at 673 K for 3.6 ks to investigate the initial stage of the nitrogen supersaturation process without the formation of iron and chromium nitrides. SEM-EDX, electron back-scattering diffraction (EBSD), and TEM analyses were utilized to [...] Read more.
Martensitic stainless steel type AISI420 was plasma nitrided at 673 K for 3.6 ks to investigate the initial stage of the nitrogen supersaturation process without the formation of iron and chromium nitrides. SEM-EDX, electron back-scattering diffraction (EBSD), and TEM analyses were utilized to characterize the microstructure of the nitrided layer across the nitriding front end. The original coarse-grained, fully martensitic microstructure turned to be α’- γ two phase and fine-grained by high nitrogen concentration. Below this homogeneously nitrided layer, α’-grains were modified in geometry to be aligned along the plastic slip lines together with the α’ to γ-phase transformation at these highly strained zones. Most of these α’-grains in the two-phase microstructure had a nano-laminated structure with the width of 50 nm. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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9 pages, 2990 KiB  
Article
Variant Selection in Fe-20Ni-1.8C under Bending
by Annick P. Baur, Cyril Cayron and Roland E. Logé
Crystals 2018, 8(12), 474; https://doi.org/10.3390/cryst8120474 - 18 Dec 2018
Cited by 5 | Viewed by 3166
Abstract
Variant selection is commonly observed in martensitic steels when a stress is applied to the material during transformation. Classically, the selection phenomenon is modelled considering the work of the shape strain in the applied stress field. This shape strain is generally calculated by [...] Read more.
Variant selection is commonly observed in martensitic steels when a stress is applied to the material during transformation. Classically, the selection phenomenon is modelled considering the work of the shape strain in the applied stress field. This shape strain is generally calculated by using the Phenomenological Theory of the Martensite Crystallography (PTMC). In the present study, we studied the martensitic transformation occurring in a Fe-20wt%Ni-1.8wt%C alloy transformed while loaded in four-point bending. A significant variant selection is observed, but surprisingly its nature cannot be explained by the classical approach. A crystallography-based empirical model which accounts for the experimental results is proposed instead. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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11 pages, 6127 KiB  
Article
Morphological and Crystallographic Characteristics of α Structure in a Low-Carbon Iron–Nickel Alloy
by Gaojun Mao, Cyril Cayron, Xiuli Mao, Rui Cao, Roland Logé and Jianhong Chen
Crystals 2018, 8(12), 468; https://doi.org/10.3390/cryst8120468 - 14 Dec 2018
Cited by 2 | Viewed by 3832
Abstract
The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, [...] Read more.
The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, it is of interest to explore possible discrepancies between lath martensite and lath bainite from a crystallographic perspective. These microstructures were obtained by various cooling rates (i.e., water quenching, 5 °C/s, and 0.05 °C/s) and then were characterized by a combination of scanning electron microscopy and electron backscattered diffraction techniques. It is shown that: (1) Lath martensite (LM) formed in the samples that were water-quenched, and a mixture of LM and lath bainite (LB) and granular bainite (GB) formed in the samples cooled at rates of 5 °C/s and 0.05 °C/s, respectively; (2) A Kurdjumov-Sachs relationship was mostly found in as-quenched martensite, while a Greninger-Troiano relationship represented the orientation relationship of LB and GB; (3) As the cooling rate decreased, the dislocation densities in corresponding microstructures were reduced, while the tendency of variant grouping was enhanced. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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12 pages, 547 KiB  
Article
A Revisit to the Notation of Martensitic Crystallography
by Yipeng Gao
Crystals 2018, 8(9), 349; https://doi.org/10.3390/cryst8090349 - 30 Aug 2018
Cited by 5 | Viewed by 3091
Abstract
As one of the most successful crystallographic theories for phase transformations, martensitic crystallography has been widely applied in understanding and predicting the microstructural features associated with structural phase transformations. In a narrow sense, it was initially developed based on the concepts of lattice [...] Read more.
As one of the most successful crystallographic theories for phase transformations, martensitic crystallography has been widely applied in understanding and predicting the microstructural features associated with structural phase transformations. In a narrow sense, it was initially developed based on the concepts of lattice correspondence and invariant plane strain condition, which is formulated in a continuum form through linear algebra. However, the scope of martensitic crystallography has since been extended; for example, group theory and graph theory have been introduced to capture the crystallographic phenomena originating from lattice discreteness. In order to establish a general and rigorous theoretical framework, we suggest a new notation system for martensitic crystallography. The new notation system combines the original formulation of martensitic crystallography and Dirac notation, which provides a concise and flexible way to understand the crystallographic nature of martensitic transformations with a potential extensionality. A number of key results in martensitic crystallography are reexamined and generalized through the new notation. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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8 pages, 3837 KiB  
Article
Microstructure and Phase Transformation Analysis of Ni50−xTi50Lax Shape Memory Alloys
by Weiya Li and Chunwang Zhao
Crystals 2018, 8(9), 345; https://doi.org/10.3390/cryst8090345 - 29 Aug 2018
Cited by 8 | Viewed by 2941
Abstract
The microstructure and martensitic transformation behavior of Ni50−xTi50Lax (x = 0.1, 0.3, 0.5, 0.7) shape memory alloys were investigated experimentally. Results show that the microstructure of Ni50−xTi50Lax alloys consists of [...] Read more.
The microstructure and martensitic transformation behavior of Ni50−xTi50Lax (x = 0.1, 0.3, 0.5, 0.7) shape memory alloys were investigated experimentally. Results show that the microstructure of Ni50−xTi50Lax alloys consists of a near-equiatomic TiNi matrix, LaNi precipitates, and Ti2Ni precipitates. With increasing La content, the amounts of LaNi and Ti2Ni precipitates demonstrate an increasing tendency. The martensitic transformation start temperature increases gradually with increasing La content. The Ni content is mainly responsible for the change in martensite transformation behavior in Ni50−xTi50Lax alloys. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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15 pages, 7225 KiB  
Article
The Effect of Martensitic Phase Transformation Dilation on Microstructure, Strain–Stress and Mechanical Properties for Welding of High-Strength Steel
by Xizhang Chen, Pengfei Wang, Qiuhong Pan and Sanbao Lin
Crystals 2018, 8(7), 293; https://doi.org/10.3390/cryst8070293 - 15 Jul 2018
Cited by 10 | Viewed by 3708
Abstract
The application of low transformation temperature (LTT) wire can effectively reduce residual stress, without the need for preheating before welding and heat treatment after welding. The mechanism reduces the martensitic transformation temperature, allowing the martensite volume expansion to offset some or all of [...] Read more.
The application of low transformation temperature (LTT) wire can effectively reduce residual stress, without the need for preheating before welding and heat treatment after welding. The mechanism reduces the martensitic transformation temperature, allowing the martensite volume expansion to offset some or all of the heat-shrinking, resulting in reduced residual stress during the welding process. In this paper, commercial ER110S-G welding wire and LTT wire with chemical composition Cr10Ni8MnMoCuTiVB were developed to solve the problem of stress concentration. The microstructure of the LTT joint is mainly composed of martensite and a small amount of residual austenite, while the microstructure of the ER110S-G joint is mainly composed of ferrite and a small amount of granular bainite. The micro-hardness and tensile strength of the LTT joint is higher than that of ER110S-G joint; however, the impact toughness of the LTT joint is not as good as that of the ER110S-G joint. The martensitic phase transformation of LTT starts at 212 °C and finishes at around 50 °C, and the expansion caused by phase transition is about 0.48%, which is much higher than that of the base metal (0.15%) and ER110S-G (0.18%). The residual tensile stress at the weld zone of the ER110S-G joint is 175.5 MPa, while the residual compressive stress at the weld zone of LTT joint is −257.6 MPa. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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55 pages, 11499 KiB  
Article
Shifting the Shear Paradigm in the Crystallographic Models of Displacive Transformations in Metals and Alloys
by Cyril Cayron
Crystals 2018, 8(4), 181; https://doi.org/10.3390/cryst8040181 - 23 Apr 2018
Cited by 26 | Viewed by 8406
Abstract
Deformation twinning and martensitic transformations are characterized by the collective displacements of atoms, an orientation relationship, and specific morphologies. The current crystallographic models are based on the 150-year-old concept of shear. Simple shear is a deformation mode at constant volume, relevant for deformation [...] Read more.
Deformation twinning and martensitic transformations are characterized by the collective displacements of atoms, an orientation relationship, and specific morphologies. The current crystallographic models are based on the 150-year-old concept of shear. Simple shear is a deformation mode at constant volume, relevant for deformation twinning. For martensitic transformations, a generalized version called invariant plane strain is used; it is associated with one or two simple shears in the phenomenological theory of martensitic crystallography. As simple shears would involve unrealistic stresses, dislocation/disconnection-mediated versions of the usual models have been developed over the last decades. However, a fundamental question remains unsolved: how do the atoms move? The aim of this paper is to return to a crystallographic approach introduced a few years ago; the approach is based on a hard-sphere assumption and linear algebra. The atomic trajectories, lattice distortion, and shuffling (if required) are expressed as analytical functions of a unique angular parameter; the habit planes are calculated with the simple “untilted plane” criterion; non-Schmid behaviors associated with some twinning modes are also predicted. Examples of steel and magnesium alloys are taken from recent publications. The possibilities offered in mechanics and thermodynamics are briefly discussed. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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