Monotonic and low cycle fatigue behavior of an O+B2 alloy at high temperatures

Low cycle fatigue behavior of an O+B2 alloy was evaluated at 650 degrees C in ambient atmosphere under fully reversed total axial strain controlled mode. Three different microstructures, namely equiaxed O plus aged B2 (fine O plates in B2 matrix), lenticular O laths plus aged B2 and a pancake composite microstructure comprising equiaxed alpha 2, lenticular O and aged B2, were selected to study the effect of microstructure on low cycle fatigue behavior in this class of alloys. Distinct well-defined trends were observed in the cyclic stress-strain response curves depending on the microstructure. The cyclic stress response was examined in terms of softening or hardening and correlated with microstructural features and dislocation behavior. Fatigue life was analyzed in terms of standard Coffin-Manson and Basquin plots and for all microstructures a prevailing elastic strain regime was identified, with a single slope for microstructures equiaxed and composite and a double slope for lenticular O laths. (c) 2014 Elsevier B.V. All rights reserved.

Anisotropic hardening model based on non-associated flow rule and combined nonlinear kinematic hardening for sheet materials

 A material model for more effective analysis of plastic deformation of sheet materials is presented in this paper. The model is capable of considering the following aspects of plastic deformation behavior of sheet materials: the anisotropy in yielding stresses in different directions by using a quadratic yield function (based on Hill’s 1948 model and stress ratios), the anisotropy in work hardening by introducing non-constant flow stress hardening in different directions, the anisotropy in plastic strains in different directions by using a quadratic plastic potential function and non-associated flow rule (based on Hill’s 1948 model and plastic strain ratios, r-values), and finally some of the cyclic hardening phenomena such as Bauschinger’s effect and transient behavior for reverse loading by using a coupled nonlinear kinematic hardening (so-called Armstrong-Frederick-Chaboche model). Basic fundamentals of the plasticity of the model are presented in a general framework. Then, the model adjustment procedure is derived for the plasticity formulations. Also, a generic numerical stress integration procedure is developed based on backward-Euler method (so-called multistage return mapping algorithm). Different aspects of the model are verified for DP600 steel sheet. Results show that the new model is able to predict the sheet material behavior in both anisotropic hardening and cyclic hardening regimes more accurately. By featuring the above-mentioned facts in the presented constitutive model, it is expected that more accurate results can be obtained by implementing this model in computational simulations of sheet material forming processes. For instance, more precise results of springback prediction of the parts formed from highly anisotropic hardened materials or that of determining the forming limit diagrams is highly expected by using the developed material model.

Deformation behaviours of coarse-grained and nanocrystalline Mg-5wt% Al alloys

Magnesium alloys have been of growing interest to various engineering applications, such as the automobile, aerospace, communication and computer industries due to their low density, high specific strength, good machineability and availability as compared with other structural materials. However, most Mg alloys suffer from poor plasticity due to their Hexagonal Close Packed structure. Grain refinement has been proved to be an effective method to enhance the strength and alter the ductility of the materials. Several methods have been proposed to produce materials with nanocrystalline grain structures. So far, most of the research work on nanocrystalline materials has been carried out on Face-Centered Cubic and Body-Centered Cubic metals. However, there has been little investigation of nanocrystalline Mg alloys. In this study, bulk coarse-grained and nanocrystalline Mg alloys were fabricated by a mechanical alloying method. The mixed powder of Mg chips and Al powder was mechanically milled under argon atmosphere for different durations of 0 hours (MA0), 10 hours (MA10), 20 hours (MA20), 30 hours (MA30) and 40 hours (MA40), followed by compaction and sintering. Then the sintered billets were hot-extruded into metallic rods with a 7 mm diameter. The obtained Mg alloys have a nominal composition of Mg–5wt% Al, with grain sizes ranging from 13 μm down to 50 nm, depending on the milling durations. The microstructure characterization and evolution after deformation were carried out by means of Optical microscopy, X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Scanning Probe Microscopy and Neutron Diffraction techniques. Nanoindentaion, compression and micro-compression tests on micro-pillars were used to study the size effects on the mechanical behaviour of the Mg alloys. Two kinds of size effects on the mechanical behaviours and deformation mechanisms were investigated: grain size effect and sample size effect. The nanoindentation tests were composed of constant strain rate, constant loading rate and indentation creep tests. The normally reported indentation size effect in single crystal and coarse-grained crystals was observed in both the coarse-grained and nanocrystalline Mg alloys. Since the indentation size effect is correlated to the Geometrically Necessary Dislocations under the indenter to accommodate the plastic deformation, the good agreement between the experimental results and the Indentation Size Effect model indicated that, in the current nanocrystalline MA20 and MA30, the dislocation plasticity was still the dominant deformation mechanism. Significant hardness enhancement with decreasing grain size, down to 58 nm, was found in the nanocrystalline Mg alloys. Further reduction of grain size would lead to a drop in the hardness values. The failure of grain refinement strengthening with the relatively high strain rate sensitivity of nanocrystalline Mg alloys suggested a change in the deformation mechanism. Indentation creep tests showed that the stress exponent was dependent on the loading rate during the loading section of the indentation, which was related to the dislocation structures before the creep starts. The influence of grain size on the mechanical behaviour and strength of extruded coarse-grained and nanocrystalline Mg alloys were investigated using uniaxial compression tests. The macroscopic response of the Mg alloys transited from strain hardening to strain softening behaviour, with grain size reduced from 13 ìm to 50 nm. The strain hardening was related to the twinning induced hardening and dislocation hardening effect, while the strain softening was attributed to the localized deformation in the nanocrystalline grains. The tension–compression yield asymmetry was noticed in the nanocrystalline region, demonstrating the twinning effect in the ultra-fine-grained and nanocrystalline region. The relationship k tensions < k compression failed in the nanocrystalline Mg alloys; this was attributed to the twofold effect of grain size on twinning. The nanocrystalline Mg alloys were found to exhibit increased strain rate sensitivity with decreasing grain size, with strain rate ranging from 0.0001/s to 0.01/s. Strain rate sensitivity of coarse-grained MA0 was increased by more than 10 times in MA40. The Hall-Petch relationship broke down at a critical grain size in the nanocrystalline region. The breakdown of the Hall-Petch relationship and the increased strain rate sensitivity were due to the localized dislocation activities (generalization and annihilation at grain boundaries) and the more significant contribution from grain boundary mediated mechanisms. In the micro-compression tests, the sample size effects on the mechanical behaviours were studied on MA0, MA20 and MA40 micro-pillars. In contrast to the bulk samples under compression, the stress-strain curves of MA0 and MA20 micro-pillars were characterized with a number of discrete strain burst events separated by nearly elastic strain segments. Unlike MA0 and MA20, the stress-strain curves of MA40 micro-pillars were smooth, without obvious strain bursts. The deformation mechanisms of the MA0 and MA20 micro-pillars under micro-compression tests were considered to be initially dominated by deformation twinning, followed by dislocation mechanisms. For MA40 pillars, the deformation mechanisms were believed to be localized dislocation activities and grain boundary related mechanisms. The strain hardening behaviours of the micro-pillars suggested that the grain boundaries in the nanocrystalline micro-pillars would reduce the source (nucleation sources for twins/dislocations) starvation hardening effect. The power law relationship of the yield strength on pillar dimensions in MA0, MA20 supported the fact that the twinning mechanism was correlated to the pre-existing defects, which can promote the nucleation of the twins. Then, we provided a latitudinal comparison of the results and conclusions derived from the different techniques used for testing the coarse-grained and nanocrystalline Mg alloy; this helps to better understand the deformation mechanisms of the Mg alloys as a whole. At the end, we summarized the thesis and highlighted the conclusions, contributions, innovations and outcomes of the research. Finally, it outlined recommendations for future work.

Cyclic pull-out strength of steel roof and wall cladding systems

When crest-fixed thin steel roof cladding systems are subjected to wind uplift, local pull-through or pull-out failures occur prematurely at their screwed connections. During high wind events such as storms and cyclones these localised failures then lead to severe damage to buildings and their contents. In recent times, the use of thin steel battens/purlins has increased considerably. This has made the pull-out failures more critical in the design of steel cladding systems. Recent research has developed a design formula for the static pull-out strength of steel cladding systems. However, the effects of fluctuating wind uplift loading that occurs during high wind events are not known. Therefore a series of constant amplitude cyclic tests has been undertaken on connections between steel battens made of different thicknesses and steel grades, and screw fasteners with varying diameter and pitch. This paper presents the details of these cyclic tests and the results.

Asymptotic solution of mode-iii crack in damaged softening materials

In this paper, a constitutive model of elasticity coupled with damage suggested by Lemaitre et al, [1] is used. The macroscopic stress-strain response of the model includes two stages: strain hardening and strain softening. The basic equation is derived for the anti-plane shear problem. Several lowest order asymptotic solutions are obtained, and assembled for the crack-tip fields.

Fixed and Best Proximity Points of Cyclic Jointly Accretive and Contractive Self-Mappings

p(>= 2)-cyclic and contractive self-mappings on a set of subsets of a metric space which are simultaneously accretive on the whole metric space are investigated. The joint fulfilment of the p-cyclic contractiveness and accretive properties is formulated as well as potential relationships with cyclic self-mappings in order to be Kannan self-mappings. The existence and uniqueness of best proximity points and fixed points is also investigated as well as some related properties of composed self-mappings from the union of any two adjacent subsets, belonging to the initial set of subsets, to themselves.

Modeling cyclic behavior of lightly overconsolidated clays in simple shear

Assessment of seismic performance and estimation of permanent displacements for submerged slopes require the accurate description of the soil's stress-strain-strength relationship under irregular cyclic loading. The geological profile of submerged slopes on the continental shelf typically consists of normally to lightly overconsolidated clays with depths ranging from a few meters to a few hundred meters and very low slope angles. This paper describes the formulation of a simplified effective-stress-based model, which is able to capture the key aspects of the cyclic behavior of normally consolidated clays. The proposed constitutive law incorporates anisotropic hardening and bounding surface principles to allow the user to simulate different shear strain and stress reversal histories as well as provide realistic descriptions of the accumulation of plastic shear strains and excess pore pressure during successive loading cycles. (C) 2000 Published by Elsevier Science Ltd. | Assessment of seismic performance and estimation of permanent displacements for submerged slopes require the accurate description of the soil's stress-strain-strength relationship under irregular cyclic loading. The geological profile of submerged slopes on the continental shelf typically consists of normally to lightly overconsolidated clays with depths ranging from a few meters to a few hundred meters and very low slope angles. This paper describes the formulation of a simplified effective-stress-based model, which is able to capture the key aspects of the cyclic behavior of normally consolidated clays. The proposed constitutive law incorporates anisotropic hardening and bounding surface principles to allow the user to simulate different shear strain and stress reversal histories as well as provide realistic descriptions of the accumulation of plastic shear strains and excess pore pressures during successive loading cycles.

Development of new approaches for the synthesis and decoding of one-bead one-compound cyclic peptide libraries

La plupart des processus cellulaires et biologiques reposent, à un certain niveau, sur des interactions protéine-protéine (IPP). Leur manipulation avec des composés chimiques démontre un grand potentiel pour la découverte de nouveaux médicaments. Malgré la demande toujours croissante en molécules capables d’interrompre sélectivement des IPP, le développement d’inhibiteurs d’IPP est fortement limité par la grande taille de la surface d’interaction. En considérant la nature de cette surface, la capacité à mimer des structures secondaires de protéines est très importante pour lier une protéine et inhiber une IPP. Avec leurs grandes capacités peptidomimétiques et leurs propriétés pharmacologiques intéressan-tes, les peptides cycliques sont des prototypes moléculaires de choix pour découvrir des ligands de protéines et développer de nouveaux inhibiteurs d’IPP. Afin d’exploiter pleinement la grande diversité accessible avec les peptides cycliques, l’approche combinatoire «one-bead-one-compound» (OBOC) est l’approche la plus accessible et puissante. Cependant, l’utilisation des peptides cycliques dans les chimiothèques OBOC est limitée par les difficultés à séquencer les composés actifs après le criblage. Sans amine libre en N-terminal, la dégradation d’Edman et la spectrométrie de masse en tandem (MS/MS) ne peuvent pas être utilisées. À cet égard, nous avons développé de nouvelles approches par ouverture de cycle pour préparer et décoder des chimiothèques OBOC de peptides cycliques. Notre stratégie était d’introduire un résidu sensible dans le macrocycle et comme ancrage pour permettre la linéarisation des peptides et leur largage des billes pour le séquençage par MS/MS. Tout d’abord, des résidus sensibles aux nucléophiles, aux ultraviolets ou au bromure de cyanogène ont été introduits dans un peptide cyclique et leurs rendements de clivage évalués. Ensuite, les résidus les plus prometteurs ont été utilisés dans la conception et le développement d’approches en tandem ouverture de cycle / clivage pour le décodage de chimiothèques OBOC de peptides cycliques. Dans la première approche, une méthionine a été introduite dans le macrocycle comme ancrage pour simultanément permettre l’ouverture du cycle et le clivage des billes par traitement au bromure de cyanogène. Dans la seconde approche, un résidu photosensible a été utilisé dans le macrocycle comme ancrage pour permettre l’ouverture du cycle et le clivage suite à une irradiation aux ultraviolets. Le peptide linéaire généré par ces approches peut alors être efficacement séquencé par MS/MS. Enfin, une chimiothèque OBOC a été préparée et criblée la protéine HIV-1 Nef pour identifier des ligands sélectifs. Le développement de ces méthodologies permttra l’utilisation de composés macrocycliques dans les chimiothèques OBOC et constitue une contribution importante en chimie médicinale pour la découverte de ligands de protéines et le développement d’inhibiteurs d’IPP.

Fadiga e comportamento tensão-deformação cíclico da liga de alumínio 7050-T7451

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2016.

SYNTHESIS OF CYCLIC AZOBENZENE ANALOGUES FOR INCORPORATION INTO OLIGONUCLEOTIDES, PEPTIDES AND POLYMERS

(A) In recent years, considerable amount of effort has contributed towards enhancing our understanding of the new photoswitch, cyclic azobenzene, particularly from the theoretical point of view. However, the challenging part with this system was poor efficiency of its synthesis from 2,2’- dinitrodibenzyl and lack of effective methods for further modification which would be useful to incorporate this system into biomolecules as a photoswitch. We report the synthesis of cyclic azobenzene and analogues from 2,2’-dinitrodibenzyl, which would allow for further incorporation of this cyclic azobenzene into biomolecules. Reaction of 2,2’-dinitrodibenzyl with zinc metal powder in the presence of triethylammonium formate buffer (pH-9.5) gave a cyclic azoxybenzene, 11,12-dihydrodibenzo[c,g][1,2]diazocine-5-oxide. The latter compound was converted into cyclic azobenzene analogues (bromo-, chloro-, cyano-, and carboxyl) through subsequent transformations. The carboxylic acid analogue was reacted with D-threoninol to give the corresponding amide, which readily undergoes photo-isomerization upon illumination with light. Upon illumination with light at 400 nm, approximately 70% of cis- isomer of amide was isomerized to trans- isomer. It was observed that cis- to trans- isomerization reached the maximum steady state of light transmission after approximately 40 min, whereas the trans- to cis- isomerization approximately acquired in 2 h to regain full recovery of light transmission. Cyclic azobenzene phosphoramidite was synthesized from DMT-protected D-threoninol linked cyclic azobenzene. (B) In recent years, there has been considerable interest invested towards the synthesis of azobenzene analogues for incorporation into proteins. Among the many azobenzene analogues, the synthesis of bi-functional cyclic azobenzene analogues for the incorporation into proteins is relatively new. In this thesis, we report the synthesis of a cyclic azobenzene biscarboxylic acid from 4-(bromomethyl)benzonitrile. (C) Azobenzene has been widely used in the field of polymer science to study the surface morphology and surface properties of polymers. In this thesis, we report the incorporation of cyclic azobenzene into a commercial polymer 2- (hydroxyethyl)methacrylate. Samples collected after 24 h from the reaction solution showed approximately 9% of incorporation of cyclic azobenzene into polymer compared to samples collected after 10 h, which showed approximately 6% incorporation.

(A) Photoregulation of DNA Functions by Cyclic Azobenzene-tethered Oligonucleotides (B) Site-specific Fluorescent Labeling of DNA using Inverse Electron Demand Diels-Alder Reaction between trans-Cyclooctene Derivatives and BODIPY-Tetrazine Adducts

(A) Most azobenzene-based photoswitches require UV light for photoisomerization, which limit their applications in biological systems due to possible photodamage. Cyclic azobenzene derivatives, on the other hand, can undergo cis-trans isomerization when exposed to visible light. A shortened synthetic scheme was developed for the preparation of a building block containing cyclic azobenzene and D-threoninol (cAB-Thr). trans-Cyclic azobenzene was found to thermally isomerize back to the cis-form in a temperature-dependent manner. cAB-Thr was transformed into the corresponding phosphoramidite and subsequently incorporated into oligonucleotides by solid phase synthesis. Melting temperature measurement suggested that incorporation of cis-cAB into oligonucleotides destabilizes DNA duplexes, these findings corroborate with circular dichroism measurement. Finally, Fluorescent Energy Resonance Transfer experiments indicated that trans-cAB can be accommodated in DNA duplexes. (B) Inverse Electron Demand Diels-Alder reactions (IEDDA) between trans-olefins and tetrazines provide a powerful alternative to existing ligation chemistries due to its fast reaction rate, bioorthogonality and mutual orthogonality with other click reactions. In this project, an attempt was pursued to synthesize trans-cyclooctene building blocks for oligonucleotide labeling by reacting with BODIPY-tetrazine. Rel-(1R-4E-pR)-cyclooct-4-enol and rel-(1R,8S,9S,4E)-Bicyclo[6.1.0]non-4-ene-9-ylmethanol were synthesized and then transformed into the corresponding propargyl ether. Subsequent Sonogashira reactions between these propargylated compounds with DMT-protected 5-iododeoxyuridine failed to give the desired products. Finally a methodology was pursued for the synthesis of BODIPY-tetrazine conjugates that will be used in future IEDDA reactions with trans-cyclooctene modified oligonucleotides.

Excitation of Phonons in Solids and Nanostructures by Intense Laser and XUV Pulses and by Low Energy Atomic Collision

Intensive, ultrakurze Laserpulse regen Festkörper in einen Zustand an, in dem die Elektronen hohe Temperaturen erlangen, während das Gitter kalt bleibt. Die heißen Elektronen beeinflussen das sog. Laser-angeregte interatomare Potential bzw. die Potentialenergiefläche, auf der die Ionen sich bewegen. Dieses kann neben anderen ultrakurzen Prozessen zu Änderungen der Phononfrequenzen (phonon softening oder phonon hardening) führen. Viele ultrakurze strukturelle Phänomene in Festkörpern hängen bei hohen Laseranregungen von Änderungen der Phononfrequenzen bei niedrigeren Anregungen ab. Um die Laser-bedingten Änderungen des Phononenspektrums von Festkörpern beschreiben zu können, haben wir ein auf Temperatur-abhängiger Dichtefunktionaltheorie basierendes Verfahren entwickelt. Die dramatischen Änderungen nach einer Laseranregung in der Potentialenergiefläche werden durch die starke Veränderung der Zustandsdichte und der Besetzungen der Elektronen hervorgerufen. Diese Änderungen in der Zustandsdichte und den Besetzungszahlen können wir mit unserer Methode berechnen, um dann damit das Verhalten der Phononen nach einer Laseranregung zu analysieren. Auf diese Art und Weise studierten wir den Einfluss einer Anregung mit einem intensiven, ultrakurzen Laserpuls auf repräsentative Phonon Eigenmoden in Magnesium, Kupfer und Aluminium. Wir stellten dabei in manchen Gitterschwingungen entweder eine Abnahme (softening) und in anderen eine Zunahme (hardening) der Eigenfrequenz fest. Manche Moden zeigten bei Variation der Laseranregungsstärke sogar beide Verhaltensweisen. Das eine Phonon-Eigenmode ein hardening und softening zeigen kann, wird durch das Vorhandensein von van Hove Singularitäten in der elektronischen Zustandsdichte des betrachteten Materials erklärt. Für diesen Fall stellt unser Verfahren zusammen mit der Sommerfeld-Entwicklung die Eigenschaften der Festkörper Vibrationen in Verbindung mit den Laser induzierten Veränderungen in den elektronischen Besetzungen für verschiedene Phonon-eingefrorene Atomkonfigurationen. Auch die absolute Größe des softening und hardening wurde berechnet. Wir nehmen an, dass unsere Theorie Licht in die Effekte der Laseranregung von verschiedenen Materialien bringt. Außerdem studierten wir mit Hilfe von Dichtefunktionaltheorie die strukturellen Material-Eigenschaften, die durch kurze XUV Pulse induziert werden. Warme dichte Materie in Ultrakurzpuls angeregten Magnesium wurde analysiert und verglichen mit den Ergebnissen bei durch Laser Anregung bedingten Änderungen. Unter Verwendung von elektronischer-Temperatur-abhängiger Dichtefunktionaltheorie wurden die Änderungen in den Bindungseigenschaften von warmen dichten Magnesium studiert. Wir stellten dabei beide Effekte, Verstärkung und Abschwächung von Bindungen, bei jeweils verschiedenen Phonon Eigenmoden von Magnesium auf Grund von der Erzeugung von Rumpflöchern und dem Vorhandensein von heißen Elektronen fest. Die zusätzliche Erzeugung von heißen Elektronen führt zu einer Änderung der Bindungscharakteristik, die der Änderung, die durch die bereits vorhandenen Rumpflöcher hervorgerufen wurde, entgegen wirkt. Die thermischen Eigenschaften von Nanostrukturen sind teilweise sehr wichtig für elektronische Bauteile. Wir studierten hier ebenfalls den Effekt einer einzelnen Graphen Lage auf Kupfer. Dazu untersuchten wir mit Dichtefunktionaltheorie die strukturellen- und Schwingungseigenschaften von Graphen auf einem Kupfer Substrat. Wir zeigen, dass die schwache Wechselwirkung zwischen Graphen und Kupfer die Frequenz der aus der Ebene gerichteten akustischen Phonon Eigenmode anhebt und die Entartung zwischen den aus der Ebene gerichteten akustischen und optischen Phononen im K-Punkt des Graphen Spektrums aufhebt. Zusätzlich führten wir ab initio Berechnungen zur inelastischen Streuung eines Helium Atoms mit Graphen auf einem Kuper(111) Substrat durch. Wir berechneten dazu das Leistungsspektrum, das uns eine Idee über die verschiedenen Gitterschwingungen des Graphene-Kuper(111) Systems gibt, die durch die Kollision des Helium Atom angeregt werden. Wir brachten die Positionen der Peaks im Leistungsspektrum mit den Phonon Eigenfrequenzen, die wir aus den statischen Rechnungen erhalten haben, in Beziehung. Unsere Ergebnisse werden auch verglichen mit den Ergebnissen experimenteller Daten zur Helium Streuung an Graphen-Kupfer(111) Oberflächen.

Finite element simulations of the cyclic elastoplastic behaviour of copper thin films

A large-scale computational and statistical strategy is presented to investigate the development of plastic strain heterogeneities and plasticity induced roughness at the free surface in multicrystalline films subjected to cyclic loading conditions, based on continuum crystal plasticity theory. The distribution of plastic strain in the grains and its evolution during cyclic straining are computed using the finite element method in films with different ratios of in-plane grain size and thickness, and as a function of grain orientation (grains with a {1 1 1} or a {0 0 1} plane parallel to the free surface and random orientations). Computations are made for 10 different realizations of aggregates containing 50 grains and one large aggregate with 225 grains. It is shown that overall cyclic hardening is accompanied by a significant increase in strain dispersion. The case of free-standing films is also addressed for comparison. The overall surface roughness is shown to saturate within 10 to 15 cycles. Plasticity induced roughness is due to the higher deformation of {0 0 1} and random grains and due to the sinking or rising at some grain boundaries.

Role of microstructure in the low cycle fatigue of multi-phase steels

The low cycle fatigue (LCF) behaviour of several commercially-produced multiphase steels was studied; including dual-phase (DP) and transformation induced plasticity (TRIP). In addition, a novel TRIP980 hybrid microstructure was examined that consisted of coarse ferrite grains along with low temperature bainite regions interspersed with retained austenite. Fully reversed strain controlled fatigue tests were conducted on the different steels to determine the cyclic stress response and strain to failure. The effects of the cyclic deformation on the microstructures were analysed using electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). Results showed that the initial cyclic hardening behaviour and low cyclic softening ratio observed in the TRIP steels was not necessarily due to austenite to martensite transformation. Differences between the austenite transformation behaviour of the conventional and novel hybrid TRIP microstructures was related to the different surrounding phases and the size of the retained austenite.