Showing papers in "Materials Science and Technology in 2014"
TL;DR: In this article, a summary of the most recent improvements on selected NiTiHf-based alloys is presented to point out their significant shape memory pro-tects, including shape memory effect under high stress (above 500 MPa) and superelasticity above 100°C.
Abstract: NiTiHf-based shape memory alloys have been receiving considerable attention for high temperature, high strength and two-way shape memory applications since they could have transformation temperatures above 100°C, shape memory effect under high stress (above 500 MPa) and superelasticity above 100°C. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf-based alloys have some drawbacks such as low ductility and high slope in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. It has been revealed that microstructural control is crucial to govern the shape memory properties (e.g. transformation temperatures, matrix strength, shape recovery strain, twinning type, etc.) of NiTiHf-based alloys. A summary of the most recent improvements on selected NiTiHf-based systems is presented to point out their significant shape memory pro...
139 citations
TL;DR: A review of enzyme mediated biodegradation of various polymers including synthetic, natural and blends of these materials is presented in this paper, where detailed examples of enzymatic degradation of polymers are illustrated with the discussion on various factors that can influence the degradation.
Abstract: Recently, research on polymer has drawn much attention mainly due to the ever increasing application of these polymeric materials in several areas such as food packaging industry, agricultural industry and biomedical research. However, increasing industrial use of polymers has led to the environmentally critical issue of waste disposal. Further, the successful implication of polymeric materials in biomedical applications depends on the biodegradability of the concerned polymer. Various enzymes play an important role in the biodegradation of polymers. The present review describes the enzyme mediated biodegradation of various polymers including synthetic, natural and blends of these materials. Detailed examples of enzymatic degradation of polymers are illustrated from current scientific literature with the discussion on various factors that can influence the degradation. In addition, different techniques that are generally applied to assess the degradation process as well as degradation products have been described. Finally, a special emphasis is given to the investigation of the kinetics of polymer degradation by enzymes.
122 citations
TL;DR: In this article, the alloy design concepts of high performance austenitic FeMnAlC steels, namely, Simplex and alloys strengthened by nanoscale ordered κ-carbides, are introduced.
Abstract: We introduce the alloy design concepts of high performance austenitic FeMnAlC steels, namely, Simplex and alloys strengthened by nanoscale ordered κ-carbides. Simplex steels are characterised by an outstanding strain hardening capacity at room temperature. This is attributed to the multiple stage strain hardening behaviour associated to dislocation substructure refinement and subsequent activation of deformation twinning, which leads to a steadily increase of the strain hardening. Al additions higher that 5 wt-% promote the precipitation of nanoscale L′12 ordered precipitates (so called κ-carbides) resulting in high strength (yield stress ∼1·0 GPa) and ductile (elongation to fracture ∼30%) steels. Novel insights into dislocation–particle interactions in a Fe–30·5Mn–8·0Al–1·2C (wt-%) steel strengthened by nanoscale κ-carbides are discussed.
106 citations
TL;DR: In this article, the authors highlight the unique combination of physicochemical and thermomechanical characteristics associated with metal organic framework (MOF) type materials and illustrate emergent applications in three challenging technological sectors: energy, environmental remediation and biomedicine.
Abstract: This review is concerned with the recent advances in metal organic framework (MOF) materials. We highlight the unique combination of physicochemical and thermomechanical characteristics associated with MOF-type materials and illustrate emergent applications in three challenging technological sectors: energy, environmental remediation and biomedicine. MOFs represent an exciting new class of nanoporous crystalline solids constituting metal ions/clusters and multifunctional organic linkages, which self-assemble at molecular level to generate a plethora of ordered 3D framework materials. The most intriguing feature of a MOF lies in its exceptionally large surface area, far surpassing those of the best activated carbons and zeolites. Next generation multifunctional materials encompassing MOF based thin films, coatings, membranes and nanocomposites have potential for exploitation in an immense array of unconventional applications and smart devices. We pinpoint the key technological challenges and basic scientific questions to be addressed, so as to fulfil the translational potential for bringing MOFs from the laboratory into commercial applications.
94 citations
TL;DR: In this paper, the current technical issues preventing the widespread application of Mg sheet alloys in automobiles (cost, mechanical properties and formability, joining, corrosion resistance) are assessed and future research needs to develop viable Mg Sheet alloys for these applications are identified.
Abstract: Increasing global demands for energy conservation and environmental protection have prompted automotive manufactures to develop lightweight automobiles. As the lightest of structural alloys, Mg alloys offer significant potential for weight reduction, but have yet to see significant application in automobiles, particularly in sheet form. The current technical issues preventing the widespread application of Mg sheet alloys in automobiles (cost, mechanical properties and formability, joining, corrosion resistance) are assessed and future research needs to develop viable Mg sheet alloys for these applications are identified.
93 citations
TL;DR: In this article, the effects of different thermomechanical treatments on the R-phase transformation of NiTi alloys have been reviewed, and recent work on controlling the R phase transformation temperature by low temperature aging treatments is summarized.
Abstract: In near equiatomic NiTi alloys, the thermoelastic transformation between austenite and the R-phase shows unique properties, which make the R-phase transformation very promising for applications. In the present paper, the fundamental issues related to the R-phase transformation, especially the effects of different thermomechanical treatments, are reviewed. Inspired by the literature review, recent work on controlling the R-phase transformation temperature by low temperature aging treatments is summarised.
80 citations
TL;DR: In this paper, the development of new Mg alloys and their corrosion characteristics in detail are discussed along with the future challenges that need to be addressed and the latest advancements in coating of Mg alloy to control their degradation rate.
Abstract: Mg and its alloys become natural biomaterials as the elemental Mg is found in the human body in abundance and their mechanical properties being akin to the natural bone as well as due to their inherent bioabsorbable/bioresorbable property. This paper discusses the development of new Mg alloys and their corrosion characteristics in detail. The latest advancements in coating of Mg alloys to control their degradation rate are also reviewed along with the future challenges that need to be addressed.
74 citations
TL;DR: In this article, the authors reveal the scientific and technological developments of a consortium sharing a common intrigue and interest for a unique microstructure, nanostructured bainite.
Abstract: It is not the first time that a consortium of steel makers, end users and scientists end up with unique approaches and developments in the physical metallurgy of steels. The present paper reveals the scientific and technological developments of a consortium sharing a common intrigue and interest for a unique microstructure, nanostructured bainite. Also known as low temperature bainite, its unique properties rely solely on the scale of the miscrostructure obtained by heat treatment at low temperature (150–350°C). Careful design based on phase transformation theory, some well known metallurgy facts and the necessary industrial experience were the ingredients for a further step towards the industrialisation of these microstructures.
69 citations
TL;DR: The magnetic shape memory effect can be classified as an example of the multiferroic effect combining ferro-elasticity and (ferro)magnetism.
Abstract: The magnetic shape memory effect can be classified as an example of the multiferroic effect combining ferro-elasticity and (ferro)magnetism. After short overview of all known effects the focus is on magnetic field induced structure reorientation (MIR) in the martensite of Ni–Mn–Ga. In this material giant deformations of up to 12% have been observed in moderate magnetic fields. The phenomenology of the effect is first discussed and a model presented. The properties of Ni–Mn–Ga relevant to MIR are then considered. One necessary condition for MIR is a highly mobile twin boundary or interface between two differently oriented martensite variants (ferroelastic domains). In 10M modulated martensite, two types of mobile twin boundary (type I and type II) are observed with complex layered microstructures consisting of a hierarchy of twinning systems. The boundaries strongly differ according to the magnitude and temperature dependence of the twinning stress. Finally, the nature of these boundaries and their...
67 citations
TL;DR: Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, such as small-scale wireless networks.
Abstract: Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, ...
60 citations
TL;DR: In this article, various strategies to induce self-healing behavior in fiber reinforced polymer based composites are discussed and a distinction is made between the extrinsic and intrinsic healing strategies.
Abstract: This paper addresses the various strategies to induce self-healing behaviour in fibre reinforced polymer based composites. A distinction is made between the extrinsic and intrinsic healing strategies. These strategies can be applied at the level of the fibre, the fibre/matrix interface or at the level of the matrix. It is shown that the degree of healing depends on the type of damage and the testing mode used and examples are given both for extrinsic and for intrinsic healing systems. The conclusion is drawn that self-healing in fibre reinforced composites is possible yet unlikely to become a commercial reality in the near future.
TL;DR: In this article, the effect of temperature rise on flow stress and strain on AZ31 magnesium alloy deformation curves was investigated and corrected flow curves were employed to develop the constitutive model, which showed that flow stress reaches a peak value and then decreases to steady values.
Abstract: Isothermal compression tests at temperatures ranging from 523 to 723 K and strain rates from 0·01 to 10 s−1 were performed on AZ31 magnesium alloy to reveal the deformation characteristics. The flow stress–strain curves show that the flow stress reaches a peak value and then decreases to steady values, which characterise a dynamic flow softening. The measured flow stress was modified by friction and temperature correction, which reflect the friction corrected flow stresses are lower than the measured ones and the effect of temperature rise on flow stress is obvious at high strain rate (≧1 s−1). The corrected flow curves were employed to develop the constitutive model. The influence of strain was also incorporated in the constitutive equation by considering the effects of strain on material constants, which were identified using sixth order polynomial. The flow stress predicted by the constitutive model shows good agreement with the corrected stress, which confirmed that the proposed model is effec...
TL;DR: In this article, the authors determined the kinetics of the martensitic transformation in Fe −0·80C from dilatometry data and showed no significant variation when the cooling rate is changed by two orders of magnitude.
Abstract: The kinetics of the martensitic transformation in Fe–0·80C has been determined from dilatometry data and shows no significant variation when the cooling rate is changed by two orders of magnitude All kinetic data can be adequately simulated by the Koistinen and Marburger (KM) equation using a specific start temperature TKM and rate parameter αm This finding supports the suggestion that the transformation is athermal, and moreover, the absence of a time dependence strongly indicates that autocatalytic nucleation does not contribute to the transformation kinetics in plain carbon steels on measurable time scales Furthermore, dilatometry experiments with different austenitising conditions were conducted to examine the effect of the prior austenite grain size on the overall kinetics of martensite formation The present results indicate that the progress of martensite formation beyond a fraction f = 0·15 is independent of the prior austenitising treatment It is therefore concluded that austenite–aus
TL;DR: In this paper, the development of austenite grain structures have been compared in two different microalloyed steels (Nb-Ti and Nb-V steels) and one Al killed C-Mn steel, after soaking at 950-1250°C for 1 h.
Abstract: Development of austenite grain structures have been compared in two different microalloyed steels (Nb–Ti and Nb–V steels) and one Al killed C–Mn steel, after soaking at 950–1250°C for 1 h. Minimum austenite grain size in Nb–V steel at the lower soaking temperature ( 1200°C) in all the steels. Higher stability of TiN precipitate restricted the grain growth in Nb–Ti steel at higher soaking temperature. An effort has been made to predict the austenite grain size considering both solute drag and Zener drag.
TL;DR: In this paper, non-metallic inclusions (NMIs) nucleate fatigue damage by causing changes in the subsurface microstructure, including white etching regi...
Abstract: The connection between the cleanliness of 52100 type bearing steels and their reliability has been well documented. Most research over the past 30 years has focused on sensitive compositional control during metallurgical refinement, leading to steels so clean that industrial cleanness standards are no longer suitable for quantifying further improvements. There is less literature, however, detailing the mechanism by which different impurities initiate rolling contact fatigue (RCF). Early work focused on comparing fatigue lives with cleanness ratings, which include a worst field analysis to determine the inclusion content and post-failure analysis to determine damage nucleation sites. The stress concentrations around discontinuities in the steel matrix can now however be visualised using computational modelling techniques. There is now a much clearer picture of how non-metallic inclusions (NMIs) nucleate fatigue damage by causing changes in the subsurface microstructure, including white etching regi...
TL;DR: In this article, the influence of the carbide that precipitates during various heating processes on austenitisation kinetics and amount of retained austenite was investigated, and it was found that a considerable amount of Mn rich cementite particles precipitated when heating was interrupted at 550°C for 5 min; they remained undissolved during short intercritical annealing at 650°C, impairing the ATK and decreasing the fraction of retained Austenite.
Abstract: To retain a large fraction of austenite in 5 wt-%Mn alloyed transformation induced plasticity (TRIP) steel after short intercritical annealing (IA), the influence of the carbide that precipitates during various heating processes on austenitisation kinetics and amount of retained austenite was investigated. It was found that a considerable amount of Mn rich cementite particles precipitated when heating was interrupted at 550°C for 5 min; they remained undissolved during IA at 650°C, impairing the austenitisation kinetics and decreasing the fraction of retained austenite. In contrast, relatively fine para-carbide particles precipitated extensively, without Mn enrichment, when heating was interrupted at 250°C for 20 min. Both, experimental investigations and numerical simulations, indicate that these para-carbide particles were quickly dissolved during IA, thereby accelerating the austenitisation kinetics and increasing the fraction of retained austenite. In addition, the influence of the heating rate was in...
TL;DR: In this paper, the development of the novel grade 38MnB5 was reported, which achieved proof strength in excess of 1400 MPa and ultimate tensile strength of 2000 MPa following hot stamping.
Abstract: The automotive industry is under increasing pressure to: (1) reduce the weight of vehicles and (2) improve crash performance. ‘Hot stamped’ mild carbon–manganese–boron steel 22MnB5 has become common place in the body structure of the European vehicle over the past decade. The ultrahigh strength martensitic microstructure resulting from hot stamping (proof strength ∼1200 MPa and ultimate tensile strength ∼1500 MPa) enables down gauging while not compromising crash performance. However, with demands for yet higher strength in the final component so to enable further down gauging, novel grades must be developed. In this paper, development of the novel grade 38MnB5 was reported. Following hot stamping, 38MnB5 demonstrated proof strength in excess of 1400 MPa and ultimate tensile strength in excess of 2000 MPa. Owing to the immense strength, the novel grade 38MnB5 was considered to offer significant down gauging and weight reduction opportunities to the automotive industry.
TL;DR: In this paper, the microstructure of aircraft gas turbine engine bearing steel has been characterised after service in RollsRoyce Trent™ engines, with the focus on surface condition and the consequences of sliding contact.
Abstract: The microstructure of aircraft gas turbine engine bearing steel has been characterised after service in Rolls-Royce Trent™ engines, with the focus on surface condition and the consequences of sliding contact. Carbide populations at the surfaces of rolling elements are found depleted by 30% after 30 000 h engine service. A single ball failure occurred after this period, leading to fatigue spalling that initiated below the contact surface. Comparisons between unused bearing raceways and those that have experienced service revealed that the microstructures resulting from secondary hardening remain remarkably stable. Plastic flow along the direction of rolling is confined to a shallow zone <2 μm beneath the contact surfaces. Transmission electron microscopy has revealed a new deformation mechanism in these bearing steels, in the form of mechanical twinning at interfaces and prior austenite grain boundaries. It is demonstrated that workhardening occurs to a depth of 1 mm in the raceway that has experie...
TL;DR: In this paper, the microstructure and mechanical properties of the HR3C austenite heat resistant steel were investigated after artificial aging at 650°C for time up to 3000 h.
Abstract: Microstructure and mechanical properties of the HR3C austenite heat resistant steel were investigated after artificial aging at 650°C for time up to 3000 h. The results show that as the aging time increased, the room temperature tensile and impact fracture mechanisms of the HR3C steel change from trans- to intergranular fracture. M23C6 type carbides and MX type carbonitrides continuously precipitate during aging, leading to the change of the mechanical properties and fracture mode of the steel. Moreover, the dissolution of the coherent twins and the transformation from the incoherent twins to the thermodynamically stable austenite subgrains have great effects on the mechanical properties of the aged steel, too. When increasing the aging time to ≧2000 h, the microstructure and mechanical properties of the steel are nearly constant, indicating a good thermal stability of the HR3C steel at elevated temperature.
TL;DR: A particular interest has been placed on embedding these sensors into advanced composites for in situ manufacturing process monitoring and then, lifetime structural health monitoring (SHM) as discussed by the authors, and there is no doubt that the need of maintaining structural integrity of these composites has been increased owing to an increasing use of carbon and glass fibre composites in real life structural and engineering applications.
Abstract: Fibre-optic Bragg grating (FBG) sensors have been recognised as one of the smart localised and globalised structural health monitoring devices for many structural applications. A particular interest has been placed on embedding these sensors into advanced composites for in situ manufacturing process monitoring and then, lifetime structural health monitoring (SHM). There is no doubt that the need of maintaining structural integrity of these composites has been increased owing to an increasing use of carbon and glass fibre composites in real life structural and engineering applications. In the public transportation, the structural components of Airbus 350 XWB and Boeing 787 are made by over 50% of composite materials to replace traditional aluminium alloys. Electric vehicles have used lightweight carbon fibre composites as their chassis to overcome the weight penalty from batteries. With the advantages of high specific stiffness to weight ratio and good damping properties of polymer based composites...
TL;DR: In the reverse route, these nanocrystallites form large disordered aggregates followed by surface crystallisation to create a thin, highly crystalline, dense shell and, finally, an extension of the crystallisation from the surface to the core as discussed by the authors.
Abstract: Investigation of the early stage morphologies of some organic and inorganic systems has established that their crystal growth does not always follow the classical route established 120 years ago. The classical theory assumes that a highly symmetric crystal develops from the nucleation and repeated attachment of atoms, molecules or ions to a single nucleus. In instances where surfactants or polymers are introduced, the crystal growth is often found, however, to follow a ‘reversed crystal growth’ route. This non-classical growth route is initiated by organic molecules adsorbed onto the surface of the nanocrystallites in the early stages of growth. In the reversed route, these nanocrystallites form large disordered aggregates followed by surface crystallisation to create a thin, highly crystalline, dense shell and, finally, an extension of the crystallisation from the surface to the core. Although systems following a non-classical crystal growth route have been known for many years, their formation m...
TL;DR: The current state of the art of materials research using multi-objective genetic and evolutionary algorithms is briefly presented with critical analyses in this paper, focusing on the achievements to date and the specific needs for further improvement.
Abstract: The current state of the art of materials research using multi-objective genetic and evolutionary algorithms is briefly presented with critical analyses. The basic concepts of multi-objective optimisation and Pareto optimality are explained in simple terms and the advantages of an evolutionary approach are emphasised. Current materials related research in this area is summarised, focusing on the achievements to date and the specific needs for further improvement.
TL;DR: In this article, the relationship between the stability and physical parameters of cubic structure has been investigated from the view of the atomic size difference, mixing enthalpy, electronegativity difference and valence electron concentration in as cast high entropy alloys.
Abstract: According to the experimental dataset on the as cast high entropy alloys with cubic structure, the relationship between the stability and physical parameters of cubic structure has been investigated from the view of the atomic size difference, mixing enthalpy, electronegativity difference and valence electron concentration in the present work to reveal the stability and structure formation in as cast high entropy alloys. The results indicated that the mixing enthalpy is the effective parameter that can predict the stability of solid solutions in as cast high entropy alloys. The atomic size difference, electronegativity difference and valence electron concentration also play important roles in the formation of body centred cubic and face centred cubic crystals. Moreover, the back propagation artificial neural network was established using data collected from the calculated solid solution physical parameters and the structure characteristic of as cast high entropy alloys, and the structure of alloys...
TL;DR: In this article, a three-dimensional heat and mass flow model was used to assess tool durability and define the domains of satisfactory tool life in the context of welding difficult aluminium alloys.
Abstract: In previous work, we have established a scheme that exploits a three-dimensional heat and mass flow model to assess tool durability and define the domains of satisfactory tool life in the context of welding difficult aluminium alloys. We now apply this scheme to the friction stir welding of steel and extend the calculations to cover consequences on the microstructure of the steel while optimising tool life. This is the first published model that covers both the processing parameters and the consequences on the physical metallurgy of the steel.
TL;DR: In this paper, the influence of elevated Co and Ti levels on the mechanical properties of Ni-base superalloy RR1000 has been investigated, and the modified alloys exhibited a higher proof stress than RR1000 across the entire 20 to 800°C temperature range.
Abstract: The influences of elevated Co and Ti levels on the mechanical properties of the Ni-base superalloy RR1000 have been investigated. Following heat treatment, the modified alloys had the typical γ–γ′ microstructure, with γ′ precipitate sizes comparable to similarly heat treated RR1000, but with a slightly higher volume fraction. The modified alloys exhibited a higher proof stress than RR1000 across the entire 20 to 800°C temperature range investigated. Superior creep rupture lives, when compared to RR1000, were observed in the modified alloys at 700°C, but not at 750°C, where extensive precipitation of topologically close packed σ phase occurred on the grain surfaces. The formation of this deleterious phase was linked to Cr and Mo enrichment of the γ matrix, caused by the elevated Co and Ti additions.
TL;DR: In this paper, a combined experimental and theoretical investigation of discrete twin boundary motion in ferromagnetic shape memory alloys 10M NiMnGa is presented, which leads to identification of two intrinsic energy barriers that dominate twinning kinetics and possible mechanism for overcoming these barriers.
Abstract: Combined experimental and theoretical investigation of discrete twin boundary motion in ferromagnetic shape memory alloys 10M NiMnGa is presented. Motion of individual boundaries is studied through mechanical tests and pulsed magnetic field experiments. Analysis of the experimental results leads to identification of two intrinsic energy barriers that dominate twinning kinetics and possible mechanism for overcoming these barriers. At low velocities, the twinning stress property is dictated by a long range (micrometre scale) periodic potential. At higher rates, a short range (nanometre scale) potential, which is related to the periodicity of the lattice, is responsible for the transition in kinetic behaviour from slower thermally activated to faster athermal motion. These observations enable formulation of different kinetic relations that are valid at different ranges of the driving force. The derived relations show a very good fit to the experimental results, allowing quantitative extraction of fun...
TL;DR: In this paper, a numerical approach to investigate the surface layer characteristics after ultrasonic surface rolling process (USRP), which is a severe plastic deformation process involving complex static extrusion and dynamic impact, is presented.
Abstract: The present paper presents a numerical approach to investigate the surface layer characteristics after ultrasonic surface rolling process (USRP), which is a severe plastic deformation process involving complex static extrusion and dynamic impact. Efforts are made in the development of finite element model (FEM), accompanied by assessment of material constitutive relation and meshing accuracy as well as definition of loading condition according to the technological principle of USRP. The majority of processing parameters have been taken into account, and results are discussed in terms of residual stress, surface roughness and workhardening. As supplied 40Cr disc was subjected to ultrasonic surface rolling for validation of FEM, and the residual stresses predicted from the FEM are in good agreement with the measurements obtained by X-ray diffraction method, indicating that the present FEM can be used as a fast prediction tool for the design of ultrasonic surface rolling parameters.
TL;DR: In this paper, an enzymatic degradation of nanohybrid based on intercalation of chitosan within the galleries of montmorillonite (MMT) clay and grafted with poly(lactic acid) (PLA) was studied using esterase enzyme in phosphate buffered solution.
Abstract: Enzymatic degradation of nanohybrid based on intercalation of chitosan (CS) within the galleries of montmorillonite (MMT) clay and grafted with poly(lactic acid) (PLA) was studied using esterase enzyme in phosphate buffered solution. Chitosan was first intercalated between the galleries of natural unmodified sodium MMT clay and subsequently grafted with PLA to prepare nanohybrids of CS-g-PLA/MMT. The prepared membranes were characterised by X-ray diffraction, transmission electron microscopy and NMR spectroscopy. The specimens were then subjected to enzymatic degradation to understand the effect of copolymerisation with PLA and the effect of incorporation of MMT in the CS matrix. The presence of MMT clay provided stability towards degradation of polymer matrix because of nanoscale dispersibility, thereby acting as a barrier towards the permeation of water molecules to induce hydrolysis of PLA. Similarly, the grafting of CS with crystalline PLA stabilised the CS matrix towards degradation, renderin...
TL;DR: In this article, the dependence of stress on temperature and strain rate was fitted to a sinh-Arrhenius equation and characterised by the Zener-Hollomon parameter with apparent activation energy of 208·3 kJ mol−1.
Abstract: Deformation behaviour of AA6061 alloy was investigated using uniaxial compression tests at temperatures from 400 to 500°C and strain rates from 0·01 to 1 s−1. Stress increases to a peak value, then decreases monotonically until reaching a steady state. The dependence of stress on temperature and strain rate was fitted to a sinh-Arrhenius equation and characterised by the Zener–Hollomon parameter with apparent activation energy of 208·3 kJ mol−1. Grain orientation spread analysis by electron backscattered diffraction indicated dynamic recovery and geometrical dynamic recrystallisation during hot compression. Deformation at a faster strain rate at a given temperature led to finer subgrains, resulting in higher strength. Dynamic precipitation took place concurrently and was strongly dependent on temperature. Precipitation of Q phase was found in the sample deformed at 400°C but none at 500°C. A larger volume fraction of precipitates was observed when samples were compressed at 400°C than at 500°C.
TL;DR: In this paper, a set of angular parameters based on the classic work of Kurdjumov and Sachs in the 1930s were used to provide a unified and elegant description facilitating extraction and detailed statistical treatment of OR from large electron backscatter diffraction datasets, as well as straightforward comparison with named OR and with the predictions from the phenomenological theory.
Abstract: Transformations from austenite to martensite or bainite in ferrous alloys have great technological importance, but some aspects remain elusive. The orientation relationship (OR), morphology and habit plane can vary considerably from one system to another. Much published work considers these OR in terms of their variation from named relationships such as Kurdjumov–Sachs and Nishiyama–Wassermann. We discuss here, instead, the use of a set of angular parameters based on the classic work of Kurdjumov and Sachs in the 1930s, that provide a unified and elegant description facilitating extraction and detailed statistical treatment of OR from large electron backscatter diffraction datasets, as well as straightforward comparison with named OR and with the predictions from the phenomenological theory. Spatially correlated mappings of OR parameters obtained using this approach suggest that the observed variations in OR are related to the martensitic morphology rather than being an experimental artefact.