Cyril Cayron- Ph.D (EPFL, 2000), HDR (CEA, 2012)
- Scientific collaborator at Swiss Federal Institute of Technology in Lausanne
Cyril Cayron
- Ph.D (EPFL, 2000), HDR (CEA, 2012)
- Scientific collaborator at Swiss Federal Institute of Technology in Lausanne
Senior Scientist
About
219
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5,274
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Introduction
Current institution
Additional affiliations
September 2014 - present
October 2000 - August 2014
Education
September 1992 - August 1995
Ecole Nationale Supérieure des Mines de Nancy
Field of study
- Engineering
Publications
Publications (219)
Native metals of igneous origin are recognized as one of the distinctive features of basalts from the Moon. Our study demonstrates that the tiny Fe-Ni metal blebs nucleated from lunar magma exhibit unanticipated, nutshell-like, crystallographic microstructures, that can be used in conjunction with local variations in chemical compositions to trace...
Laser Powder Bed Fusion (LPBF) stations mostly use lasers with a Gaussian beam intensity distribution, as it has advantages like small divergence and high ability to be focused. This distribution creates significant thermal gradients leading to high cooling rates, which promote the formation of an α’‐martensitic structure in Ti‐6Al‐4V. While this m...
Understanding complex microstructures required crystallography and math. Two examples: martensite treated by group theory and twins treated by number theory
This study elucidates the evolution of martensite deformation via Interaction Work (IW). The IW is the mechanical work done by external loading, assisting deformation by competing with the energy barrier. This interplay establishes the maximum IW (IW max) criterion for variant selection of different deformation modes. Considering multiple deformati...
A brief overview on the crystallography martensite and deformation twins:
- Concepts: lattice distortion, orientation, correspondence, variants, PTMC, simple shear, invariant plane strain, hard-sphere, angular distortion, correspondence theory
- Materials: steels, titanium alloys, NiTi shape memory alloys, magnesium.
Two severe plastic deformation (SPD) techniques of simple shear extrusion (SSE) and equal channel angular pressing (ECAP) were employed to process an extruded Mg−6Gd−3Y−1.5Ag (wt%) alloy at 553 K for 1, 2, 4 and 6 passes. The microstructural evolutions were studied by electron back scattered diffraction (EBSD) analysis and transmission electron mic...
We agree with Lin et al.’s comment Lin et al.’s (2022). The interpretation we proposed to explain the twins formed in a single crystal of magnesium (Cayron and Logé, 2018) was not correct.
In the past few years, laser powder-bed fusion (LPBF) of high entropy alloys (HEAs) has gained significant interest. We investigated a HEA (PdPtRhIrCuNi) elaborated by LPBF, and studied its microstructure and mechanical properties. This alloy has potential applications in luxury industries, as well as in medical technologies. The microstructure con...
Variant reorientation is a ubiquitous phenomenon in shape memory alloys and has a great influence on their texture and mechanical response. In the present study, a martensitic NiTi rolled sheet is investigated by the electron backscattering diffraction (EBSD) technique; the variant reorientation and texture evolution are followed during bending. Th...
We employ flash infrared annealing to investigate the phase transition of formamidinium lead triiodide (FAPbI3) thin films for their solar cell applications. Measuring the enthalpy changes of the FAPbI3 composition at different heating rates allows us to calculate an activation energy of 1.8 eV for the black perovskite phase transition. We explore...
To find the best Cu % and Mg/Si ratio and optimize the heat treatments in 6xxx alloys, we need to answer the following questions: What are the crystallographic structures of the nano-precipitates? What is their precipitation sequence? Do they dissolve to re-precipitate in other forms or do they "evolve" during their growth? The aim of the presentat...
It is generally assumed that the parent-twin interface is a fully invariant plane. The calculations of the rational interfaces of the type I twins and irrational interfaces of the type II twins are based on this hypothesis. Recently, some asymmetric facets and unconventional twins have been observed in magnesium that do not agree with this paradigm...
Effects of chromium (Cr) content on types and morphologies of various phases of a newly developed Co–Ni–Al–W superalloy (Co-30Ni-6W-9Al-3Ti-1Ta) have been investigated in this study. Microstructural examinations were carried out by field-emission scanning electron microscope (FESEM), electron backscatter diffraction (EBSD), high-resolution transmis...
Given N integers a,b,c.... find other small integers such that au + bv + cw + .. = 1 (Bézout's identity), and find also other small integers such that au + bv + cw +... = 0 (integer relation). Not so easy !
This presentation explains how lattices can be reduced by hyperplane shearing and how this method can be used to find solutions to Bézout's ide...
The correspondence theory explains why the junction planes of type I twin between the martensite variants are generic rational planes, and why the 180° rotation axes of the type II twins are generic rational directions, and how they can be easily calculated from the correspondence matrix and the symmetry matrices of the parent phase. The lattice pa...
The production of superheated melt during hypervelocity impact events has been proposed to be a common occurrence on terrestrial planetary bodies. Recent direct evidence of superheated impact melt temperatures exceeding >2370°C from the Kamestastin (Mistastin Lake) impact structure, Canada, was based on a single impact glass sample. Such high super...
We present a systematic investigation of {101¯2} extension twinning mechanism in single crystal magnesium micropillars deformed over seven orders of magnitude of strain rate, from 10–4 to 500 s⁻¹, revealing how the accommodation of newly formed twins evolves with and depends on the kinetic compatibility of interfacial processes when high deformatio...
The is an extended version of a presentation that will be given at ICOMAT 2022 in March 2022. It gives the details of a new approach of the crystallography of martensite transformations. The twins between the variants are deduced from the parent symmetries that constitute the inter-correspondence operators. The relative roles of symmetries and metr...
Martensite crystallography is usually described by the phenomenological theory of martensite crystallography (PTMC). This theory relies on stretch matrices and compatibility equations, but it does not give a global view on the structures of variants, and it masks the relative roles of the symmetries and metrics. Here, we propose an alternative theo...
Printing gold alloys parts is a challenge due to the high reflectivity and thermal conductivity of these materials. Recent studies show an improvement in printing gold using the Laser Powder Bed Fusion (LPBF) process; however, the impact of the A1→L10 phase transformation on printed red-gold alloy has not been studied. In this work, 3D printed red-...
A geometric method of lattice reduction based on cycles of directional and hyperplanar shears is presented. The deviation from cubicity at each step of the reduction is evaluated by a parameter called ‘basis rhombicity’ which is the sum of the absolute values of the elements of the metric tensor associated with the basis. The levels of reduction ar...
Recently, a new thermally activated distortion with amplification (TADA) effect has been reported in red gold alloys caused by the A1 → L10 phase transformation. The macroscopic amplification is due to the persistence of variant selection nucleated under stress but growing in stress-free condition. In this work, we show that the TADA effect can gen...
![Fig. 9. SAED pattern in the zone axis ZA = [0 0 1] of the copper matrix...](profile/Baptiste-Rouxel/publication/357326246/figure/fig5/AS:1115785003044868@1643035283580/SAED-pattern-in-the-zone-axis-ZA-0-0-1-of-the-copper-matrix-for-the-specimen-a_Q320.jpg)
Cu-Be alloys provide excellent electrical and mechanical properties, but present serious health hazards during manufacturing. Among alternative alloys, the Cu-Ti system has the highest yield strength; however, Ti cannot be easily solutionized at concentrations above 4 wt%, resulting in a relatively low formability. In this study, Cu-xTi-yFe (x = 3,...
We reaffirm that the high-resolution electron microscopy image used by Jenkins and Smith as a proof of the existence of a 9R structure of the Cu nanoprecipitates in iron alloy results from a moiré effect. The herringbone motif in the image can be interpreted as an interference between the body centred cubic lattice of iron and the same lattice cont...
Deformation twinning on a plane is a simple shear that transforms a unit cell attached to the plane into another unit cell equivalent by mirror symmetry or 180° rotation. Thus, crystallographic models of twinning require the determination of the short unit cells attached to the planes, or hyperplanes for dimensions higher than 3. Here, a method is...
Two magnesium alloys with the nominal compositions of Mg−6Gd−3Y (GW63) and Mg−6Gd−3Y−1Ag (GW63−1Ag) were hot extruded and then processed by 6 passes of the simple shear extrusion (SSE) process at 553 K. Both SEM and EBSD studies confirmed the mean grain size reduction of the extruded base GW63 alloy from 10.1 to 2.9 μm by adding 1 wt% Ag. This decr...
An extruded Mg–6Gd−3Y−0.5Ag magnesium alloy was processed by the simple shear extrusion (SSE) technique at 553 K for 1, 2, 4 and 6 passes to refine the microstructure. The electron back scattered diffraction (EBSD) analysis was used to investigate the microstructural evolutions of the alloy after the SSE processing. The grain orientation spread (GO...
Lattice reduction is a NP-hard problem well known in computer science and cryptography. The Lenstra-Lenstra-Lovasz (LLL) algorithm based on the calculation of orthogonal Gram-Schmidt (GS) bases is efficient and gives a good solution in polynomial time. Here, we present a new approach called cubification that does not require the calculation of the...
The paper explains the method to determine a short unit cell attached to any hyperplane given by its integer vector p. Equivalently, it gives all the solutions of the N-dimensional Bézout's identity associated with the coordinates of p.
![Fig. 2. Simulation of the SAED of Fig. 4 of [1] . (a-c) Experimental...](profile/Cyril-Cayron/publication/346017422/figure/fig1/AS:959499041001477@1605773806686/Simulation-of-the-SAED-of-Fig-4-of-1-a-c-Experimental-SAED-from-1-b_Q320.jpg)
![Fig. 3. Simulation of the SAED of Fig.7 of [1] . (a) Experimental SAED....](profile/Cyril-Cayron/publication/346017422/figure/fig2/AS:959499040985093@1605773806718/Simulation-of-the-SAED-of-Fig7-of-1-a-Experimental-SAED-b-Simulation-with_Q320.jpg)
Recently, a hexagonal phase has been reported in high carbon steels in several studies. Here, we show that the electron microscopy results used in these studies were erroneously interpreted. The extra-spots in the diffraction patterns and the odd contrasts in the high resolution images are not those a superstructure but result from double diffracti...
The current theory of twin crystallography is based on the concept of invariant plane. The present paper extends the theory to encompass the cases of heterotwins in which the composition plane is only quasi-invariant.
Accurately constraining the formation and evolution of the lunar magnesian suite is key to understanding the earliest periods of magmatic crustal building that followed accretion and primordial differentiation of the Moon. However, the origin and evolution of these unique rocks is highly debated. Here, we report on the microstructural characterizat...
Difficulties with joining oxide dispersion-strengthened (ODS) steels using classical welding processes have led to the development of alternative joining techniques such as spark plasma sintering (SPS). SPS, which is classically employed for performing sintering, may also be used to join relatively large components due to the simultaneous applicati...
Variant selection during the A1→L10 transformation in a polycrystalline red gold alloy close to equiatomic Au-Cu composition has been extensively studied by Electron Back Scattered Diffraction (EBSD) in our previous work. The use of a mathematical description of the lattice distortion and the maximal work criterion allowed us to quantify the degree...
The complex and intricate microstructure of B19' martensite in shape memory nickel titanium alloys is generally explained with the Phenomenological Theory of Martensitic Crystallography (PTMC). Over the last decade, we have developed an alternative approach that supposes the existence of a "natural" parent-daughter orientation relationship (OR). As...
G115 steel has gained a growing interesting recently for its use in next-generation ultra-supercritical power plant applications. Due to the high densities of dislocations and lath martensite boundaries in G115 steel, interactions between solutes and dislocations result in unique microstructural evolution during creep with the formation of dense Cu...
This presentation just aims at promoting a method that could be useful. As the manuscript in Arxviv (under review) seems not so easy to read, I decided to explain the method with 11 slides (among which 4 are reminder about matrices and determinants).
Earth-abundant semiconducting materials are a potential solution for large-scale deployment of solar cells at a lower cost. Zinc phosphide (Zn3P2) is one such Earth-abundant material with optoelectronic properties suitable for photovoltaics. Herein, we report the van der Waals epitaxy of tetragonal Zn3P2 (α-Zn3P2) on graphene using molecular beam e...
Constrained optimization problems exist in all the domain of science, such as thermodynamics, mechanics, economics etc. For more than two centuries, these problems have been solved with the help of the Lagrange multipliers and the Lagrangian function. This method has however the disadvantage that it adds the number of constraint equations to the di...
The crystallography of twinning is based on the concepts of simple shear and obliquity introduced by Mügge, Mallard and Friedel at the turn of the last century, with tensor mathematics later developed by Bilby, Bevis and Crocker in the 1960s. We propose a synthesis of these works by writing the three transformations (distortion, orientation and cor...
A shape-memory effect is known to appear in red gold alloys with compositions close to Au–Cu. The aim of this paper is to study by electron backscatter diffraction (EBSD) the variant selection in the A1 → L10 transformation occurring under stress, in bending conditions. The L10 domains are successfully identified by this technique despite the c/a r...
Appendices B4 and B5 of Cayron [Acta Cryst. (2019), A75, 411–437] contain equations involving the point group and the metric tensor in which the equality symbol should be substituted by the inclusion symbol.
It is established that the annealing twin boundaries of austenite act as nucleation sites for the martensitic transformation. In the present study, we observe that in surface martensite the transformation only takes place for twin boundaries that are approximately vertical in respect with the sample free surface. This phenomenon is shown to be rela...
Deformation twinning is assumed to be a simple shear. The associated mechanism is often described in term of disconnections. Within this paradigm, many funadmental questions remain unsoved. We propose to imagine deformation twinning as a phase transformation (driven by stress), without imposing the simple strain condition to the atomic displacement...
The effect of tensile deformation on variant selection has been studied in {225}γ plate martensite and {557}γ lath martensite formed in high- and low-carbon steels, respectively. Different thermomechanical treatments are performed to analyse the effect of applied tensile stress, in the elastic and plastic range and the effect of prior plastic tensi...
The crystallography of displacive/martensitic phase transformations can be described with three types of matrix: the lattice distortion matrix, the orientation relationship matrix and the correspondence matrix. Given here are some formulae to express them in crystallographic, orthonormal and reciprocal bases, and an explanation is offered of how to...
The effect of powder size distribution and oxygen content on the extent of multiple twinning and spatial distribution of oxide inclusions in hot isostatic pressed (HIPed)316L steels was investigated using powders with different characteristics. Modifications to, and differences in their microstructural topology, were tracked quantitatively by evalu...
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 [...]
Massive transformation, as a non-conventional solid-state phase transformation mode, is scarcely observed in metals with hexagonal closed packed (HCP) structure, especially in Zr and its alloys. In this study, however, we report the massive transformation in a Zr-1.0Cr-0.4Fe alloy after conventional β-quenching. It is shown that the necessary condi...
A new combination of laser scanning confocal microscope (LSCM) and electron backscattering diffraction (EBSD) with a field-emission scanning electron microscope (SEM) is utilized to study the mechanism of bainite transformation in reheated low carbon bainitic weld metal. The LSCM observations show that laths grow on the surface at various rates, fr...
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 Crystall...
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 t...
An investigation was conducted to systematically explore the relationships among microstructure evolution, continuous cooling transformation kinetics, and mechanical properties development in a low-carbon reheated weld metal (0.052C-1.5Mn-0.3Si-0.7Cr-0.8Mo-0.014Ti-0.004V-4Ni, wt.%). Microstructure was characterized by optical microscopy, scanning e...
The crystallography of displacive phase transformations can be described with three types of matrices: the lattice distortion matrix, the orientation relationship matrix, and the correspondence matrix. The paper gives some formula to express them in crystallographic bases, orthonormal bases, and reciprocal bases, and it explains how to use them to...
In the 1990s, precipitation in AlMgSiCu alloys was like a zoo of metastable phases with the usual beta” and beta’, but also the type-A, type-B and type-C reported by Matsuda, and the L and Q’ phases in alloys containing copper. All appear in TEM as nanometric rods or laths along the <100>Al directions. No crystallographic link between them was esta...
and zchen@lut.cn 2. Experiments One low-carbon high alloy weld metal was selected to in-situ observe the morphology change of surface bainite during isothermal holding by laser scanning confocal microscope (LSCM), and the other was put into furnace and then suffered from water quenching to obtain martensite. The first confocal sample was cut in to...
Constraining the timing and intensity of Solar System bombardment is critical to understanding planetary formation, evolution and habitability. However, the identification and dating of shockmetamorphic events in the mafic igneous lithologies that dominate planetary materials remains highly challenging, particularly at relatively modest shock press...
Four metal powder flux-cored wires with added nickel (Ni) were designed to systematically investigate how Ni influences the microstructure and toughness in low-carbon bainitic weld metals (WMs). The microstructure was safely predicted by utilizing reasonable welding craft parameters (i.e., appropriate heat input and proper interpass temperature). M...
Twinning is an important deformation mode of hexagonal close-packed metals. The crystallographic theory is based on the 150-year-old concept of simple shear. The habit plane of the twin is the shear plane; it is invariant. This article presents electron backscatter diffraction observations and crystallographic analysis of a millimetre-size twin in...
Low-carbon martensitic steels are made of intricate assemblies of martensitic laths: the twenty-four lath variants are grouped into packets on the four {111}fcc planes, and each packet is composed of three blocks of pairs of low-misoriented variants. The orientation relationship between the laths and their parent austenitic grains ranges from Kurdj...
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 mar...
A new combination of laser scanning confocal microscope (LSCM) and electron backscattering diffraction (EBSD) with a field-emission scanning electron microscope (SEM) is utilized to study the mechanism of bainite transformation in reheated low carbon bainitic weld metal. The LSCM observations show that laths grow on the surface at various rates, fr...
The and twinning modes were recently discovered by Ostapovets et al. [Philos. Mag. (2017), 97, 1088–1101] and interpreted as – double twins formed by the simultaneous action of two twinning shears. Another interpretation is proposed here in which the two conjugate twinning modes result from a one-step mechanism based on a (58°, a + 2b) prototype st...
Bolide impacts influence primordial evolution of planetary bodies because they can cause instantaneous melting and vaporization of both crust and impactors. Temperatures reached by impact-generated silicate melts are unknown because meteorite impacts are ephemeral, and established mineral and rock thermometers have limited temperature ranges. Conse...
A significant variant selection is reported in isothermal martensite formed on the surface of an Fe–30% Ni sample. The selection phenomenon is modelled using different descriptions of the martensitic phase transformation. In particular, matrices based on the phenomenological theory of martensite crystallography, the Jaswon and Wheeler distortion, a...
Twinning is an important deformation mode of hexagonal close-packed metals. The crystallographic theory is based on the 150-years old concept of simple shear. The habit plane of the twin is the shear plane, it is invariant. Here we present Electron BackScatter Diffraction observations and crystallographic analysis of a millimeter size twin in a mag...
The {11-22} and {11-26} twinning modes were recently put in evidence by Ostapovets et al. (Phil. Mag, 2017)and interpreted as {101-2}-{101-2} double-twins formed by a simultaneous action of two twinning shears. We propose another interpretation in which the twinning modes result from a one-step mechanism based on the same (58deg, a+2b) prototype st...
![Fig. 5. Burgers' model of bcc-hcp transformation, from Ref. [29]. The...](profile/Cyril-Cayron/publication/317888174/figure/fig19/AS:668721316114433@1536446994092/Burgers-model-of-bcc-hcp-transformation-from-Ref-29-The-two-simultaneous-shears-are_Q320.jpg)
Deformation twinning and martensitic transformations are displacive transformations; they are defined by high speed collective displacements of the atoms, the existence of a parent/daughter orientation relationship, and plate or lath morphologies. The current crystallographic models of deformation twinning in metals are based on the 150 year-old co...
Contraction twinning in magnesium alloys leads to new grains that are misoriented from the parent grain by a rotation (56°, a). The classical shear theory of deformation twinning does not specify the atomic displacements and does not explain why contraction twinning is less frequent than extension twinning. The paper proposes a new displacive model...
Low-alloy steels are constituted of twenty-four variants of lath martensite that exhibit gradients of orientations from Kurdjumov-Sachs (KS) to Nishiyama-Wassermann (NW). They are structured into four packets on each of the common close-packed plane {111}fcc // {110}bcc ; and each packet is composed of three blocks constituted by pairs of low-misor...
Questions
Questions (2)
The twinning dislocations, also called disconnections, are supposed to explain the formation of mechanical twins and martensite. The typical example is the hcp martensite formed from fcc austenite by the coordinate displacements of regularly spaced 1/6 <112> Shockley partial dislocations on {111} planes. In order to explain the origin of these dislocations, some scientists imagined a pole mechanism in which a unique dislocation would spiral around a “pole”. To my knowledge, this mechanism could not be confirmed by TEM. Then, it seems that the question was just forgotten whereas the theory of twinning dislocation has remained. My idea is that actually it is the twin or the martensite itself that produce the dislocations to accommodate the incompatibilities with the surrounding matrix, but that means that dislocations cannot explain the twin or the martensite formation because a phenomena cannot be explained by its consequence. I am ready to change my mind if anyone can reply to the question: where the twinning dislocations come from? Some TEM images showing the sources of twinning dislocations would be welcome.
Grain boundary engineering is a concept developed in the 1980-1990s that would like to increase materials properties by increasing the fraction of coincidence site lattice (CSL) boundaries with low sigma values (typically <30). However, after 20 years of EBSD on many different materials I never encountered a polycrystalline material that would exhibit a fraction of Sigma5, Sigma 7, Sigma 11, Sigma13, or Sigma15, with a frequency higher than random (ie higher than Mackenzie distribution). I conclude that the concept of low-CSL networks and related percolation theory promoted is actually not relevant for most of the metallurgical alloys. The only special boundaries are Sigma3n (Sigma3, Sigma9, etc) in low stacking fault metals, and for sure such materials have special properties thanks to their large twin related domains (and not because of an hypothetical network of low CSL). Could anyone show me an EBSD map of a polycrystalline material with high frequencies of low Sigma CSL that are not 3, 9 or 27? It would help me to change my mind.
