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Yasmin Ahmed Salem
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Scientific Events

Scientific Events

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Alloys for Additive Manufacturing Symposium 2017

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AAMS17

As Additive Manufacturing technologies are being adopted in more and more industries, the focus of research and development is shifting to the materials in use. Additionally, an increasing number of researchers in academia and industry realise the potential of Additive Manufacturing to produce materials that were heretofore inaccessible by conventional manufacturing techniques or not economically feasible. The Alloys for Additive Manufacturing Symposium aims to be a venue for the discussion of these issues by researchers in academia and application. All materials scientific issues pertaining to the additive manufacturing of metals, alloys and composites including a metallic phase fall under the scope of this conference. [more]

Introducing high temperature intermetallic eutectic as potential structural materials

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Introducing high temperature intermetallic eutectic as potential structural materials

Intermetallic fascinated high temperature materials community for the last five decades. Starting with gamma TiAl, both Ti based and Ni based single phase intermetallics have been subject of extensive investigation. It took five decades for actual application in latest generation GE engine. However, very little attention has been given to multiphase multicomponent intermetallics. These, in particular eutectics, are abundant in the central regions of phase diagrams of ternary and higher components. With a hypothesis that they represent exciting opportunity, this talk will present the outline of our fairly extensive efforts in developing high temperature intermetallic composites based on a novel design of materials through microstructural engineering of intermetallics at nano scale. We shall concentrate on the Ni-Al-Zr system and show that unique complex multiphase microstructures could be developed containing intermetallics of Ni3Al, Ni5Zr, Ni7Zr2 and NiAl. The microstructures contain single or multiple coupled eutectics that are distributed seamlessly along the entire samples. For example, for an alloy Ni-12At%Al-11at%Zr, two intermetallic phases (Ni3Al and Ni5Zr) are seamlessly distributed along the entire sample with two different length scales and morphologies. Often these microstructures can be visualised by a 3D analysis that shows variations of connectivity among phases. Many of these alloys show strength in excess of 2GPa This architecture exhibits excellent high temperature microstructural stability, exceptional high strength with reasonable tensile ductility at high temperature. We show that this can be derived from an approach designed to exploit eutectic reactions that combine Intermetallics in a microstructural scale that restricts slip lengths to obtain both strength and ductility. Some of these alloys also have exceptional oxidation resistance that is retained up to a temperature of 973K. Finally we shall present some results of creep strength of these alloy that hints at the stress induced transformation. [more]

3D materials characterization at all length scales and its applications to iron and steel

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Symposium: 3D materials characterization at all length scales and its applications to iron and steel

The atomic and micro-scale structures of most materials are 3D, but a lack of tools for experimental 3D investigation of materials has limited most published research, including simulation and modelling, to 2D datasets. In the 21st century this situation has changed significantly. New 3D characterization and modelling methods are generating powerful insights into materials properties and microstructure formation on all length scales. [more]

Symposium “Environmental, in-situ and time-resolved microscopy” at MC 2017 (Microscopy Conference 2017)

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Symposium “Environmental, in-situ and time-resolved microscopy” at MC 2017 (Microscopy Conference 2017)

MPIE Colloquium

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Size Effects in Metals: On the Role of Internal Boundaries across the Scales

Size effects are a key ingredient to control and improve the mechanical behaviour of metallic microstructures and miniaturized components. The analysis of size effects in metals has received continuous attention in the past two decades, both experimentally and numerically. This lecture focuses on the role of grain and phase boundaries in restricting dislocation motion, giving rise to size effects. Some essential features of a thermodynamically consistent model for a grain boundary are presented, which accounts for the grain boundary energy and defect structure and evolution. The role of a phase boundary is investigated with a dislocation transport driven crystal plasticity model, revealing the explicit role of the plastic phase contrast and phase boundary resistance. Interesting size effects are thereby recovered. Size effects can also be eliminated or inhibited by other microstructural mechanisms. Two cases are addressed to illustrate this. The first case reveals the role of dislocation climb and its effectiveness in dissolving dislocation pile-ups. The second case concerns a very thin austenitic film in martensite, whereby the particular structure of the phase and its interface give rise to preferential sliding mechanisms that circumvent the common dislocation driven size effects.This lecture addresses the strengthening role of internal boundaries, constituting a major con- tribution to size effects in metals. It is shown that besides dislocation pile-ups, other mechanisms may be essential. For grain boundaries, the defect absorption and redistribution matters. For phase boundaries, phase contrast in dislocation transport alone already contributes to size effects. Moreover, dislocation-pile ups can be dissolved through climb at higher temperatures or circum- vented by other particular micromechanisms. This analysis effectively illustrates that predicting size effects in metals quantitatively remains a major challenge. References [1] van Beers P.R.M., Kouznetsova V.G., Geers M.G.D.: Defect redistribution within a continuum grain boundary plasticity model. J. Mech. Phys. Solids 83:243-262, 2015.[2] Dogge M.M.W., Peerlings R.H.J., Geers M.G.D.: Interface modeling in continuum dislocation transport. Me- chanics of Materials. 88:30-43, 2015.[3] Geers M.G.D., Cottura M., Appolaire B., Busso E.P., Forest S.,Villani A.: Coupled glide-climb diffusion- enhanced crystal plasticity. J. Mech. Phys. Solids. 70:136-153, 2014.[4] Maresca F., Kouznetsova V.G., Geers M.G.D.: Subgrain lath martensite mechanics: a numerical-experimental analysis. J. Mech. Phys. Solids. 73:69-83, 2014.[5] Maresca F., Kouznetsova V.G., Geers M.G.D.: Deformation behaviour of lath martensite in multi-phase steels. Scripta Materialia 110:74-77, 2016.[6] Maresca F., Kouznetsova V.G., Geers M.G.D.: Predictive modeling of interfacial damage in substructured steels: application to martensitic microstructures. Mod. Sim. Mat. Sc. Engng. 24(2):025006, 2016.[7] Du C., Hoefnagels J.P.M, Vaes R., Geers M.G.D.: Block and sub-block boundary strengthening in lath marten- site, Scripta Materialia,116:117-121, 2016.[8] Du C., Hoefnagels J.P.M, Vaes R., Geers M.G.D.: Plasticity of lath martensite by sliding of substructure boundaries, Scripta Materialia 120:37-40, 2016. [more]

MPIE Colloquium

10352 1498039052

Some Methods and Applications of Data-driven Inference in Materials Science Some Methods and Applications of Data-driven Inference in Materials Science

Experiments and simulations in materials science and engineering often generate prodigious quantities of data. Extracting information from this data turns out to be more challenging than may at first appear, prompting efforts to create innovative ways of analyzing “big data.” I will provide an overview of my own adventure in data-driven materials research and focus in on a few methods and example applications that have proven to be especially productive. The first deals with the inference of failure criteria for individual microstructure features from databases of individual failure events. The second concerns mining and analysis of image data from the open literature to gain new insight into materials without performing any new experiments or simulations. I will conclude with some thoughts about the future of data-based methods in materials science and engineering. [more]

 
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