Show filters Hide filters

Refine your search

Publication Year
1-31 out of 31 results
Change view
  • Sort by:
30:51 University of Cambridge English 2013

Reliable ab initio methods

A lecture given by Tony Paxton, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Electron theory in the understanding of iron, its magnetic properties and the behaviour of intersitials such as hydrogen and carbon in iron. An argument is made that the well established tight binding approximation to the electronic structure now furnishes us with a reliable theory for the description of the three phases of pure magnetic iron and its principal interstitials, including carbon and hydrogen. This will open the way in the coming five years to fully quantum mechanical atomistic simulations of steel and its embrittlement by hydrogen. Some key questions have recently been answered using density functional theory, namely: what are the equilibrium concentrations of vacancy-carbon and vacany-hydrogen point defects? Can hydrogen dissolve exothermically in ferrite through its binding to defects? Do carbon atoms form "dimer molecules" when bound to vacancies in ferrite? The tight binding theory can also answer these question quantitatively as I shall show, and moreover this is a theory that can be implemented with sufficient speed in a computer to admit molecular dynamics and statics simulations well out of the reach of density functional theory. Soon we will be able to answer questions such as, how do carbides act as traps for hydrogen? How deep are these traps? Are they located at the metal-carbide interface or in the depths of the precipitate? These are questions that are also just beginning to be answered using atom probe tomography, so the theory and experiment are at similar stages of this enquiry.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
32:57 University of Cambridge English 2013

Quenching and Partitioning: Science and Technology

A lecture given by John Speer, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The quench and partitioning process involves partial transformation to martensite, followed by an increase in temperature to permit the excess carbon to partition into the residual austenite. The quenching and partitioning (Q&P) concept was first introduced about a decade ago, to utilise carbon in as-quenched martensite to stabilise retained austenite and thereby enhance the mechanical properties. This presentation will provide an update of advancements made in understanding important aspects of physical metallurgy and microstructure development, within the authors laboratories and elsewhere, which have led to interest in Q&P as a potential route for producing commercial steels in volume. A variety of applications have been explored in Q&P laboratory investigations. Initial industrialisation has focused on automotive sheet steels, and substantial activity is now underway to meet aggressive near-term targets for vehicle lightweighting using Q&P steels or other novel approaches to generate microstructures with enhanced austenite fractions. The current status of some of these efforts will be reported.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
30:46 University of Cambridge English 2013

Structure and properties of a chromium-molybdenum steel modified by fullerene and carbon nanotube additions

A lecture given by I. V. Shchetinin, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. A study of what happens when exotic forms of carbon are introduced into steel by mechanical work.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:24 University of Cambridge English 2013

Friction Stir Welding of Mild Steel-Tool Durability and Steel Microstructure

A lecture given by Tarashankar DebRoy, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Mathematical modelling of the friction stir welding of steels. In previous work, we have established a scheme that exploits a combination of three-dimensional heat and mass flow models, together with fast calculation algorithms and damage accumulation models, 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 optimizing tool life. This is the first model which covers both the processing parameters and the consequences on the physical metallurgy of the steel.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
27:03 University of Cambridge English 2013

Steel composites for energy generation systems

A lecture given by Carlos Capdevila Montes, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. About oxide dispersion strengthened, mechanically alloyed steel. In order to meet future energy demands, new materials will be required to withstand extreme environments. Ferritic FeCr(Al) oxide dispersion strengthened (ODS) steels are an example of engineered steel composite that have excellent potential for use in next-generation high-temperature applications where superior creep strength and oxidation resistance is paramount. Originally designed as heat resistant steels for conventional fossil-fuel power plants, the high-Cr ODS steels are a successful example of development to overcome the issues to meet material requirements for next generation nuclear systems. In order to maintain mechanical properties under harsh conditions, i.e., combination of cyclic thermal loads, exposure to highly corrosive environments, and a hard and intense mixed proton/neutron fields, to the end of life of a component in a nuclear reactor, a highly stable microstructure is essential. Nanostructured ferritic FeCr(Al) ODS steels are ideal candidates for those applications, because these alloys usually contain a high density of Y/Al-rich and Ti/Al- rich nanoparticles, high dislocation densities and fine grains. As it is reported here, the presence of nanoscale, uniformly dispersed oxide particles act as pinning points to inhibit dislocation movement, retard recovery and recrystallization processes.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
35:57 University of Cambridge English 2013

Magneto-structural coupling

A lecture given by Igor Abrikosov, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The emphasis is on how magentic properties play a role in the properties of iron. Ab initio simulations based on the Density Functional Theory (DFT) are known as a useful tool for prediction of materials properties and for their understanding. In this talk we review recent progress in applications of DFT for Fe-based alloys. We underline a necessity to take into account explicitly temperature induced magnetic excitations. We show that magnetic and chemical interaction in Fe-based alloys are deeply interconnected, and strongly affect each other. We start with relatively simple examples, and show that there exists very strong dependence of thermodynamic properties, like elastic constants, structural distortions, and mixing enthalpies, on the underlying magnetic state in Fe alloys with Cr, Mn, Ni, V, Nb, C, and N. We then show that effective chemical interactions in steels can be tuned by its global magnetic state, which opens exciting possibilities for materials synthesis. Using first-principles theory we demonstrate that in Fe-Si system the magnetic disorder at high temperatures favour a formation of cubic Fe2Si phase with B2 crystal structure, which is not present in the alloy phase diagram. The experiment confirms the theoretical predictions, and the B2 Fe2Si alloy is synthesized from Fe-Si mixture using multianvil press.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
31:41 University of Cambridge English 2013

Non-­destructive non-contact microstructural characterization

A lecture given by Claire Davis, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Presents the enticing story about the very rapid processing of steel to produce bainitic microstructures in milliseconds. The ability to non-destructively characterize microstructure is on most steel metallurgists wish list. Electromagnetic (EM) sensors can be used to quantify key microstructural features, not only that but they can be used on-line during steel processing for feedback control. EM sensors can already be used to monitor phase transformation in-situ during cooling after hot rolling, and recent work indicates that they can be used to quantify the phase balance in dual phase steels and therefore predict strength. This may mean that mechanical testing can be avoided, or at least reduced, when producing certain grades of steel, giving large cost and time saving to the steel industry. In the future in-situ systems to measure recrystallisation during annealing, or precipitate formation during tempering may be possible. Indeed there is potential to use different parameters from the complex EM signal response to characterise different steel microstructural features.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
30:30 University of Cambridge English 2013

Superbainite - Laboratory Concept to Commercial Product

A lecture given by Andrew Rose at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The talk describes the pioneering technology for the mass production of the world's first bulk nanostructured metal, the so-called superbainite that consists of slender platelets of bainitic ferrite separated by thinner films of retained austenite. Tata Steel have undertaken work to demonstrate the feasibility of superbainite for application as armour steel. The challenge was to adapt the composition to the demands of a tonnage production route, while still attaining the property advantages of superbainite. The Tata production route involves oxygen steelmaking, continuous casting and hot strip rolling, followed by downstream processing to a final form as armour plate. Each of these stages presents challenges to the production of high-strength steels. Tata Steel Research have reviewed the requirements for production of superbainite, and undertaken experimental work, including optical and electron metallography, studies of transformation behaviour, and mechanical testing, to justify the final choice of production parameters. As a result a composition and process route have been formulated which enable production of commercial casts of superbainite without danger to the process. Further development work has supported the downstream processing steps culminating in heat treatment of the material, and enabled the optimisation of the parameters involved. Metallurgical examination and testing have confirmed that this processing gives the superbainite microstructure with the expected properties. Ballistic testing has shown that superbainite armour is comparable with other armour steels competing in the same area.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
31:04 University of Cambridge English 2013

Isotropy and fatigue

A lecture given by Peter Olund, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. With the focus on steels for bearings, he talks about the role of inclusions in determining the anisotropy of fatigue properties, and of sampling volume effects. The demands of high cleanliness steel constantly increases due to the fact that higher loads are being introduced in the applications. Today there are cases where the elongated sulphide inclusions present in steel with "normal" sulphur content (around 80ppm) will cause premature fatigue failures. A clear trend is therefore reduced sulphur contents in air-melted steels. However, only increasing the desulphurization within the current process window, to produce low sulphur contents (less than 20ppm), will due to thermodynamics drastically increase the number and size of detrimental globular calcium aluminates. Re-melting process has therefore dominated the market for low sulphur steel. Recently, air-melt steel making processes have been developed to produce more isotropic low sulphur steel where the formation of large globular calcium alumina is thermodynamically suppressed. Consequently, steels produced with this process will exhibit more isotropic fatigue properties. In this work fatigue properties has been assessed for steels loaded in different directions with reference to the rolling direction for steels with different level of isotropy. Furthermore, the effect on operation temperature has been taking into account showing that moderate increases in temperature will affect the properties. This influence can be correlated to the microstructural stability, i.e. composition and structure, of the steel.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
28:48 University of Cambridge English 2013

Flash Bainite Process

A lecture given by Gary Cola, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Presents the enticing story about the very rapid processing of steel to produce bainitic microstructures in milliseconds.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
31:33 University of Cambridge English 2013

Atoms in bainite, atomic mechanisms: APMS conference

A lecture given by Francisca Garcia Caballero, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The atomic mechanism of the bainite transformation is discussed in the context of the highest resolution analytical experiments conceivable. After decades of debate on the mechanism for the formation of bainite, it is accepted that bainite grows via a displacive mechanism i.e., as plate-shaped transformation products exhibiting an invariant plane strain surface relief effect. But there is still much discussion on the diffusion or diffusionless nature of bainite. Elements of the theory are now routinely being used in the design of innovative steels and in the interpretation of a variety of experimental data. However, current experimental and theoretical understanding is limiting technological progress. The purpose of this atom probe tomography study was to track the atom distributions during the bainite reaction in steels with different carbon and silicon contents transformed over a wide range of temperatures (200-525 centigrade) to elucidate the role of reaction rate and diffusion in the formation of bainite with and without cementite precipitation. The results are providing new experimental evidence on subjects critically relevant to the understanding of the atomic mechanisms controlling bainitic ferrite formation, such as the incomplete transformation phenomenon, the carbon supersaturation of ferrite, the plastic accommodation of the surrounding austenite and cluster and carbides formation.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
35:50 University of Cambridge English 2013

Flash microstructure

A lecture given by Sundaranam Babu, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The interpretation of bainitic microstructures that develop very rapidly during flash processing. An innovative rapid heat-treating process (flash processing) that uses rapid heating to austenite phase field and quenching has been developed to produce high strength steels. Flash processing lead to tensile strengths greater than 1600 MPa and uniform elongation greater than 7%. In order to rationalise the microstructure evolution, the microstructures before and after processing were characterised. The initial microstructure contained ferrite and spherodised cementite. The final microstructure, after processing, contained a mixture of bainite and martensite with interspersed un-dissolved cementite particles. The above microstructure evolution was evaluated with computational thermodynamic and kinetic models. Interface motion between M3C diffusion couple, subjected to linear heating, supported the above microstructure evolution. The calculations show that the rapid dissolution of M3C in Fe-C system, in contrast to sluggish dissolution in Fe-Cr-C system. Generality of flash processing for wider range of steel systems is explored.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:21 University of Cambridge English 2013

Pop-in Behavior during Nanoindentation on Steel Alloy

A lecture given by Heung Nam Han, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. About the nanoindentation of steel, and the pop-in effect, variant selection. Nano-indentation is an outstanding method to probe small-scale mechanical properties, which are relevant to a wide range of materials and applications. The response of a material to nano-indentation is usually presented in the form of a loadâ€"displacement curve. It is known that nano-indentation pop-in is a sudden displacement excursion on the load-displacement curve during load-controlled indentation. The sources of pop-in might be basically geometrical softening behaviors. In this study, several physical events which cause pop-ins during nano-indentation of steel alloys will be discussed. First, we consider the onset of plasticity resulting from dislocation nucleation or dislocation source activation in ferritic steel, which can produce the geometrical softening in the early stage of mechanical contact during nano-indentation. The effect of strain aging on the nano-indentation pop-in is observed and compared to the well-known macro-scale yield drop in tensile test. Second, both strain-induced alpha prime and epsilon martensitic transformations of metastable austenite are investigated by nano-indentation of individual austenite grains in multi-phase steels. The pop-ins are described as resulting from the geometrical softening due to the selection of favorable variants of alpha prime martensite and partial dislocation for epsilon martensite, respectively.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:06 University of Cambridge English 2013

Energetic TWIP

A lecture given by David Dye, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Twinning induced plasticity steels as armour. Twinning Induced PLasticity steels have recently been popular topics of research owing to their potential for high energy adsorbtion during deformation. This is a consequence of both their propensity to twin due a an optimised stacking fault energy and also the thinness of the twins, which results in continuous work hardening and hence the avoidance of necking until very high strains are reached. However, not all of this deformation is useable in many applications; for example the hull intrusion in an armoured vehicle may not be manageable beyond a certain point. Therefore there is a desire for TWIP steels with higher initial yield strengths. Here we describe a two options to add strengthening mechanisms to austenitic TWIP steels to provide this strength without damaging the underlying twinning mechanism, and progress we have been making in implementing these in an industrially exploitable steel.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
32:41 University of Cambridge English 2013

Architectured Steel

A lecture given by Toshihiko Koseki, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Multilayered steels are described, including the theoretical framework for the design of such composites. Traditionally, physical metallurgy concerns microstructure-property correlation. In this approach, microstructure evolves as the product of interactions between composition and process parameters controlled by the thermodynamic and kinetic conditions. Attributes concerning the property are obtained as the function of volume fraction, size, shape and distribution of the constituent phases, usually described through empirical relations or even on the basis of imprecise knowledge. Hence, the approach is more evolutionary than constructive. Performance driven construction of the microstructure demands precise response and interaction of microstructural constituents under the given loading condition. An architecturally designed microstructure implies planning, design and construction of microstructure considering nature, size, morphology and distribution of the constituent phases on a suitably conceived topological framework. With the aforesaid ambition, an attempt has been proposed on construction of the ferrite-martensite microstructure, based on iso-strain architecture, aiming at maximum work hardening. In another attempt, the mechanical response of a topologically designed bimodal microstructure in single phase steel has been evaluated for maximizing the strength-ductility combination.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
32:48 University of Cambridge English 2013

Secondary-hardened bainite

A lecture given by Jer Ren Yang, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The metallurgy of a new, microalloyed bainitic steel that is capable of secondary hardening, accompanied by a simultaneous increase in strength and ductility is introduced. Ideally, a low carbon bainitic microstructure offers an excellent combination of good toughness, strength and weldability. The typical microstructure of low-carbon bainitic steels is composed of a fine substructured bainitic ferrite matrix with certain amounts of uniformly distributed carbon-rich second phases. These second phases, located among the sheaves of bainitc ferrite, consist basically of martensite/austenite (M/A) constituents. As a result of the low-angle character of boundaries of bainitic ferrite sub-unit within the sheaf structure, little or no evidence of ferrite boundaries could be detected by an optical microscope. It is worth further improving appreciation of the transformation and to evaluate the effect of substructure characteristics on the properties. The main purpose of this work was to investigate the effect of Mo addition on the development of microstructure in the hot-rolled low-carbon Nb-containing bainitic steels. The steel strips were fabricated by the combined processes of controlled-rolling and accelerated-cooling. Microstructural characterisation and mechanical testing for the corresponding strips have been investigated. The results show that the Mo addition has the advantage of producing a high volume fraction of bainite, which possesses a significant secondary hardening after tempering treatment. It is suggested that the secondary hardening effect provides an additional way to increase the strength of Nb-Mo-containing bainitic steels.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
25:34 University of Cambridge English 2013

Architectured Microstructure in Steel

A lecture given by Gautam Anand, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. About the use of finite element methods to model the development of microstructure. Physical metallurgy concerns microstructure-property correlation. In this approach, microstructure evolves as the product of interactions between composition and process parameters controlled by the thermodynamic and kinetic conditions. Attributes concerning the property are obtained as the function of volume fraction, size, shape and distribution of the constituent phases, usually described through empirical relations or even on the basis of imprecise knowledge. Hence, the approach is more evolutionary than constructive. Performance driven construction of the microstructure demands precise response and interaction of microstructural constituents under the given loading condition. An architecturally designed microstructure implies planning, design and construction of microstructure considering nature, size, morphology and distribution of the constituent phases on a suitably conceived topological framework. With the aforesaid ambition, an attempt has been proposed on construction of the ferrite-martensite microstructure, based on iso-strain architecture, aiming at maximum work hardening. In another attempt, the mechanical response of a topologically designed bimodal microstructure in single phase steel has been evaluated for maximising the strength-ductility combination.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
30:01 University of Cambridge English 2013

A Low Density Steel for Bearings

A lecture given by Hongliang Yi, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The talk is about low-density steel destined for bearing applications. Both rolling contact fatigue properties and wear resistance get improved with the increase of hardness for bearings. Large carbon content can achieve high hardness by solid solution strengthening in martensite or dispersion hardening due to carbide precipitation. Carbon decreases the martensite starting temperature and therefore increases the volume fraction of untransformed austenite that is not desired in the point view of dimensional stability since the metastable austenite could be induced to transform into martensite during service, furthermore the soft retained austenite would deteriorate the overall hardness. A novel alloy design has been proposed by high aluminium addition into the classical 52100 bearing steel to achieve the following advantages. Aluminium addition decreases the density of the steel significantly, whilst it enlarges the carbon solubility in austenite by thermodynamics and therefore more carbon is permitted to be added in this new low density bearing steel to maintain or enhance the hardness compared with conventional 52100 bearing steel. In order to validate the proposed speculation, some preliminary investigation on the designed alloy with high carbon (1.2 wt%) and high aluminium(5 wt%) will be conducted in this research, which is approximate 8 wt% lighter than the conventional 52100 alloy.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:11 University of Cambridge English 2013

The magnetic-field-induced precipitation behaviors of alloy carbides

A lecture given by Wu Kaiming, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Describes profound changes in the nature of carbides generated in steel, whilst under the influence of strong magnetic fields.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
33:06 University of Cambridge English 2013

High strength and ductile low density steels - Simplex and Kappa

A lecture given by Ivan Gutierrez-Urrutia, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Low-density steels are described. We present an overview of the ongoing activities on low-density steels at MPIE. We have developed two alloy concepts of high strength and ductile lightweight steels, namely, Simplex and Kappa steels. Simplex steels are austenitic Fe-Mn-Al-C steels with high Mn (~30 wt.%) and C (~1.2 wt.%) contents. These alloys exhibit exhibits a superior combination of strength and ductility (ultimate tensile strength of 0.9 GPa and elongation to failure of 80%) due to multiple-stage strain hardening. The development of an evolving hierarchical deformation structure consisting of dislocation configurations and twin substructures results in an outstanding permanent strain hardening. The role of the alloying elements on the underlying strain hardening mechanisms will be presented. Kappa steels are austenitic Fe-Mn-Al-C steels with high Mn (~30 wt.%), Al (~8.0 wt%) and C (~1.2 wt.%) contents. These light-weight alloys contain high volume fractions of L12-type ordered nanoprecipitates, so-called kappa carbides, conferring not only high strength (ultimate tensile strength of 1.2 GPa) but good ductility as well (elongation to failure of 40%). Multi-scale characterisation of nano-sized kappa carbides by TEM and 3D-APT provides new insights on kappa carbide-dislocation interactions.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
28:41 University of Cambridge English 2013

Soft particles

A lecture given by Toshihiro Tsuchiyama, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. How particles such as copper, which can be penetrated by dislocations in the ferrite, influence the properties. The second phases in steel, such as carbide, oxide, martensite, and so on, are usually used for enhancing work hardening to prevent the plastic instability during deformation. These hard structures are effective for increasing uniform elongation, but conversely, it tends to deteriorate the local elongation and reduction of area. To improve both uniform and local deformabilities, it would be desirable that the work hardening is enhanced by dispersed second phase in the initial stage of deformation, and then it disappears or becomes invalid in the higher strain region, leading to work softening. Authors believe that soft particles is one of possibilities to exhibit such a functional change and call it hetero-to-homo structural transition. In this report, the effect of soft Cu precipitates on tensile deformation behaviour of ferritic steel will be compared with that of hard VC carbide precipitates. In addition, the plastic deformation and mechanical dissolution behaviour of Cu particles by severe cold rolling will be demonstrated.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:37 University of Cambridge English 2013

Inoculated high-speed steel

A lecture given by Alexander Chaus, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. High-speed steel is inoculated with tungsten carbides to refine the structure. HSS are widely used in many metal-cutting tools, for which primarily high toughness is the main requirement providing their effective use in different cutting operations. The toughness of HSS is strongly affected by carbides formed during solidification of the melt. Melt treatment methods, particularly with addition of a small amount of surface-active or/and inoculating elements, have permitted the development of improved HSS with greater carbide control. In this work, additions of powder W and WC were used to improve the as cast microstructure of M2 HSS. Additions of up to 0.6 vol.% W and WC were made to the parent steel melted in an induction furnace. SEM and EDS confirmed that inoculation favoured the formation of the M6C eutectic instead of the M2C and VC ones, which prevailed in the parent steel. Under the action of inoculation, there was a refinement of the primary grains of the matrix and a transition from their typical dendritic structure in the parent steel to the microstructure with predominantly equiaxed morphology in the inoculated steels. The relationship between properties and microstructure is discussed.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
30:15 University of Cambridge English 2013

Nanostructured Steel Industrialization - A plausible reality

A lecture given by Carlos-Garcia Meteo, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Here he talks about the industrial production of two components from the world's first bulk nanostructured material, the so-called superbainite. It is not the first time that a consortium of steel makers, end users and scientists ends up with unique approaches and developments in the physical metallurgy of steels. This paper will tell the joint adventure story of a group of visionaries that share a common intrigue and interest for a unique microstructure, nanostructured bainite. Also known as low temperature bainite, as its unique properties rely solely on the scale of the microstructure obtained by heat treatment at low temperature (150-350ºC). 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.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
30:02 University of Cambridge English 2013

Mechanochemical Synthesis as a Tool for Modeling Properties of (new?) Iron Carbides

A lecture given by by Fabio Miani, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. On the synthesis of various carbides of iron, beginning with elemental powders. Mechanochemical synthesis by simple milling devices has proved to be an efficient experimental tool for the synthesis of nanosized iron carbides. Along with the milling action, which is basically affected by the specific chemistry, ball to powder ratio and milling times, simple low temperature thermal cycles are effective to stabilize structure and promote/dissolve specific phases. Some collected data by transmission Mössbauer spectroscopy will be presented, along with some considerations - by means of the analysis of the hyperfine field distribution - that will be proposed on the kinetics of the formation of iron carbides at the initial atomic composition Fe 5% C 95 %, which - to the knowledge of the authors has not been discussed before.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
31:32 University of Cambridge English 2013

Solubility of carbon in non-cubic ferrite

A lecture given by Dong-Woo Suh, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Explains how the fact that the bainitic ferrite unit cell does not have cubic symmetry explains the reluctance of the carbon to partition into austenite. Some remarkable discoveries have been made recently regarding the thermodynamic stability of carbon in ferrite, whose unit cell does not have cubic symmetry, but rather, is tetragonal. A combination of ab initio and phase stability calculations indicate that the change in symmetry leads to a dramatically modified phase diagram for the Fe-C system. The implications of this to both academic phenomena such as the reluctance of carbon to partition from ferrite into austenite, and to products of technological importance (such as the quench and partitioning process) are described.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
26:27 University of Cambridge English 2013

Voids and 30,000 atoms

A lecture given by Shinji Munetoh, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Uses molecular dynamics simulations to study the role of voids in determining the ductile fracture energy. Molecular dynamics (MD) simulations of the ductile fracture behaviour on the austenite and ferrite phases in steel were performed by using the MD cells including the voids due to the precipitates. The number of Fe atoms were around 30,000. Atomic movements were determined by solving Langevin equations with Finnis-Sinclair interatomic force. The tensile test was simulated by expanding the MD cell in one direction at?room temperature. In the case of the perfect crystalline MD cell, the shear fracture was observed in the austenite phase, and the ferrite phase caused the cup and cone fracture. In the case of the MD cell including the voids, the cup and cone fracture?were observed on both austenite and ferrite phases. The ductile fracture energy of austenite phase was the same level to that of?ferrite phase in the perfect crystalline MD cells.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
24:54 University of Cambridge English 2013

Regeneration treatment on welding of nanostructured bainite

A lecture given by K. Fang, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Nanostructured bainite is incredibly difficult to weld because of its high carbon concentration. Here an innovative method is presented to resolve the weldability. High-carbon nanostructured bainite steel is very difficult to be well welded due to poor weldability. By adopting a new technology called regeneration treatment, the welded joint has similar microstructures and mechanical properities to base metal. The effect of regeneration time (0h-120h) and temperature (230°C-270°C) on microstructures and mechanical properities was also investigated. Results show that microstructures in fusion and austenitised zones consist of two phases when regeneration time is long enough, which are nano-scale bainite ?lms separated by carbonâ€"enriched ?lms of retained austenite. However, volume fraction of retained austensite in fusion zone is a little lower than austenitised zone. With regeneration temperature increasing, volume fraction of retained austensite increases and thickness of slender platelets shows the same changing trend. The changes of microstructures have important effect on mechanical properities. By tensile and hardness test, the strength of fusion zone is lower than austenitised zone, but both increases with regeneration temperature decreasing while the elongation decreases. And the micro hardness increases when regeneration temperature decreasing. The strength of obtained welds reaches to as high as 1.7-2.1 GPa and corresponding hardness 550HV-650 HV.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
34:11 University of Cambridge English 2013

Pulsed Steels

A lecture given by Rongshan Qin, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Short electrical pulses are applied to dramatically modify the structure of steel. Pulsed electric current affects kinetic barrier in non-equilibrium processes and thermodynamic state in non-equilibrium systems. Application of the high density and short duration current pulses in steel processing enables the fabrication of novel microstructure and hence the new property. Our experimental observations have demonstrated the powerful and versatile effects of pulses on microstructure evolution in steels, e.g. pulse-induced grain coarsening, grain refinement, texture control, low temperature transformation and novel phase formation. This reveals significant potential in using electrical pulses to tailor the microstructure of steels. The preliminary theoretical understanding of the observed phenomena has been developed based on the thermodynamic consideration. Kinetic aspect of the effect of the pulses on microstructure transformation, however, is still in its very early stage and requires more attention.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
29:03 University of Cambridge English 2013

Boron: Type IV Cracking

A lecture given by Fujio Abe, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Some wonderful work on power plant steel containing boron, to prevent the pernicious type IV cracking. The addition of boron without the formation of any boron nitrides during normalizing heat treatment at high temperature minimizes the degradation in creep strength of both base metal and welded joints of 9%Cr ferritic power plant steel at 650oC and long times. The enrichment of soluble boron near prior austenite grain boundaries (PAGBs) by the segregation is essential for the reduction of coarsening rate of M23C6 carbides along boundaries in the vicinity of PAGBs, enhancing the boundary and subboundary hardening in base metal at long times, and also for the production of same microstructure between the base metal and heat-affected-zone (HAZ) in welded joints. The grain boundary segregation of boron retards the diffusive transformation from ferrite to austenite in HAZ during heating of welding, resulting in martensitic transformation. The resultant microstructure of HAZ after post weld heat treatment is substantially the same as that of base metal, indicating no Type IV fracture in HAZ of welded joints. 9Cr-3W-3Co-VNb steel with 120-150 ppm boron and 60-90 ppm nitrogen exhibits not only much higher creep strength of base metal than conventional 9%Cr steel but also substantially no degradation in creep strength due to Type IV fracture in welded joints at 650 C.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
26:41 University of Cambridge English 2013

The dilatometric and microstructural response of variant selection during alpha' transformation

A lecture given by Saurabh Kundu, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Theory for the selection of specific crystallographic variants out of all possible variant, when steel is transformed into bainite, martensite or in general, displacive phase transformation products. Variant selection during displacive transformation is popularly monitored by assessing the pole figure or ODF of the bulk texture or pole figures from single prior austenite grains and also by measuring the physical orientation of alpha' plates in the microstructure. However it is known that when variant selection occurs the shear strain associated with each alpha' plate does not get fully cancelled and it is reflected in the measured transformation strain. We have shown in this work that transformation strain is the most reliable measure for the variant selection. Mathematical models have already been developed to calculate the transformation strain under various loading conditions, and to support the same extensive experiments have been done to show how externally applied stress and plastic strain can affect the transformation strain. This data is used to describe the extent of variant selection which is further supported by EBSD results. Interesting observations has also been made on the nature of the strain during transformation. Finally mathematical models have been developed to show that variant selection has negligible influence on physical orientation of alpha' plates when transformation occurs under external stress only, but prior plastic deformation can change the orientation to a great extent.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
15:28 University of Cambridge English 2013

Adventures in the Physical Metallurgy of Steels 2013 - Introduction

The introductory remarks for the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University, by Harry Bhadeshia.
  • Published: 2013
  • Publisher: University of Cambridge
  • Language: English
out of 1 pages
Loading...
Feedback

Timings

  539 ms - page object
  407 ms - search
    9 ms - highlighting
    1 ms - highlighting/18643
    2 ms - highlighting/18599
    2 ms - highlighting/18608
    1 ms - highlighting/18596
    2 ms - highlighting/18606
    2 ms - highlighting/18632
    1 ms - highlighting/18600
    2 ms - highlighting/18598
    2 ms - highlighting/18629
    2 ms - highlighting/18642
    2 ms - highlighting/18633
    1 ms - highlighting/18607
    1 ms - highlighting/18602
    1 ms - highlighting/18597
    2 ms - highlighting/18635
    2 ms - highlighting/18630
    1 ms - highlighting/18644
    1 ms - highlighting/18640
    1 ms - highlighting/18645
    2 ms - highlighting/18638
    2 ms - highlighting/18634
    3 ms - highlighting/18637
    1 ms - highlighting/18625
    3 ms - highlighting/18627
    2 ms - highlighting/18605
    2 ms - highlighting/18601
    2 ms - highlighting/18639
    2 ms - highlighting/18636
    2 ms - highlighting/18631
    1 ms - highlighting/18628
    2 ms - highlighting/18641

Version

AV-Portal 3.8.2 (0bb840d79881f4e1b2f2d6f66c37060441d4bb2e)