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Zn, cold rolled - mechanical twins

Description

This sample was cold rolled. Zinc has a hexagonal structure so it contains only two independent slip systems. However, for slip to occur, five slip systems are required so zinc does not undergo general plasticity. Instead it forms mechanical twins as an alternative to dislocation motion to accommodate the deformation.

Subjects

alloy | mechanical twins | metal | twinning | zinc | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Fe, C 0.15 (wt%) steel, quenched.

Description

A low carbon steel quenched in order to produce martensitic plates.

Subjects

alloy | carbon | iron | martensite | metal | quenching | steel | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Tensile failure surface of a carbon fibre composite

Description

This is from the region of the fracture surface which was in tension. The fibres show clean, brittle fracture surfaces (with no fibrillation or distortion and little distortion of the matrix) and have broken at varying lengths and hence some stick out while others have left holes in the matrix. This is indicative of fibre pull-out having occurred after an initial failure of the matrix, followed by failure of the fibres themselves. This is a toughening mechanism in fibre reinforced composites. It is also involved in composite crack stopping properties; each fibre has briefly slowed the progress of the crack by opening it up along the weak fibre-matrix interface and hence blunting the crack tip. The crack therefore advances relatively slowly, with much lateral meandering.

Subjects

alignment | carbon | carbon fibres | CFC | composite material | epoxy | fibre | fracture | neutral axis | polymer composite | pull-out | reinforcement | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Changes in microstructure of a shape memory alloy (CuAlNi single crystal)

Description

Changes in microstructure of a shape memory alloy being heat treated and also mechanically deformed. A CuAlNi single crystal (2H orthorhombic phase ) is compressed (vertical axis) at room temperature, causing activation of two sequential twinning deformations. As austenite, the crystal is cube-shaped, whereas in the martensite form it is sheared. Six different sheared martensite crystals, having well - defined prism shapes (three of which appear in this video), can be created by pressing on 3 different faces of the cube. It is essential that the loading arrangement allows lateral displacements to occur. From TLP: Microstructural Changes. Video was kindly donated by Vaclav Novak and Petr Sittner, Department of Functional Materials Institute of Physics of the ASCR, Prague, Czech Republic

Subjects

microstructure | shape memory alloy | deformation | DoITPoMS | University of Cambridge | video | corematerials | ukoer

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Fe, C 0.2 (wt%), explosively deformed - mechanical twins

Description

This sample was explosively deformed so that there was insufficient time for dislocation motion to occur. Hence, mechanical twins are produced despite the b.c.c. structure of mild steel.

Subjects

alloy | carbon | iron | mechanical twins | metal | steel | twinning | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Fe, C 0.15 (wt%) steel, quenched.

Description

A low carbon steel quenched in order to produce martensitic plates.

Subjects

alloy | carbon | iron | martensite | metal | quenching | steel | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Kevlar fibre composite fracture surface

Description

Because a relatively short beam was used, significant shear stresses existed in the beam, and failure has occurred principally by shear. In this mode, the specimen splits longitudinally along planes parallel to its neutral axis, due to shear failure within the matrix and at the weak interface between fibres and matrix. Matrix porosity (and particularly the long longitudinal voids present in this specimen), the poor wetting of fibres by the resin, and poor fibre distribution will all promote failure by shear. However, it may be that this failure mechanism has been partly inhibited by poor fibre alignment since some off-axis fibres will reinforce the matrix in shear

Subjects

alignment | composite material | epoxy | fibre | fibrillation | fracture | hackle region | Kevlar | liquid crystalline polymer (LCP) | lyotropic | polymer | polymer composite | reinforcement | shear | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Changes in microstructure of a shape memory alloy (bi-crystal of austenitic CuAlNi )

Description

Changes in microstructure of a shape memory alloy being heat treated and also mechanically deformed. A bi-crystal of austenitic CuAlNi is cooled, causing transformation to the martensitic (2H orthorhombic) phase. The process is reversed in the second half of the video, as the specimen is heated again. The rate at which transformation occurs is controlled by heat flow effects. (The shear process itself tends to take place very rapidly.) The martensitic phase is internally twinned. This is very clear within the dark-coloured phase moving in from the left-hand side in the first part of this video. From TLP: Microstructural Changes. Video was kindly donated by Vaclav Novak and Petr Sittner, Department of Functional Materials Institute of Physics of the ASCR, Prague, Czech Republic

Subjects

microstructure | shape memory alloy | deformation | DoITPoMS | University of Cambridge | video | corematerials | ukoer

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Fe, C 0.2 (wt%), explosively deformed - mechanical twins

Description

This sample was explosively deformed so that there was insufficient time for dislocation motion to occur. Hence, mechanical twins are produced despite the b.c.c. structure of mild steel.

Subjects

alloy | carbon | iron | mechanical twins | metal | steel | twinning | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Fe, C 0.15 (wt%) steel, quenched.

Description

A low carbon steel quenched in order to produce martensitic plates.

Subjects

alloy | carbon | iron | martensite | metal | quenching | steel | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Kevlar fibre composite shear surface

Description

This is an image of the shear surface in a failed composite beam. 'Hackles' of matrix are clearly visible where shear has occurred within the matrix and it is also clear that shear has occurred across the fibre/matrix interface. The fibres are for the most part totally unscathed, though some mis-aligned fibres have become caught between the shear surfaces and 'fibrillated' by rolling and bending actions. It may be that this failure mechanism has been partly inhibited by poor fibre alignment since some off-axis fibres will reinforce the matrix in shear. It will have been promoted, however, by the extensive longitudinal voids.

Subjects

alignment | composite material | epoxy | fibre | fibrillation | fracture | hackle region | Kevlar | liquid crystalline polymer (LCP) | lyotropic | polymer | polymer composite | reinforcement | shear | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Fundamentals of Materials Science: Diffusion

Description

This set of animations provides an introduction to the mechanisms and driving forces of diffusion. It demonstartes some of the processes in which it is observed. From TLP: Diffusion

Subjects

diffusionsubstitutional | interstitial | random walk | Fick | law | DoITPoMS | University of Cambridge | animation | corematerials | ukoer

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Fe, Ni 30, C 0.3 (wt%), quenched - martensite plates

Description

This sample was quenched to -80 C to give a metastable martensitic microstructure. The martensite plates show a lenticular morphology as the material attempts to shear as it transforms but is unable to open up voids at the grain boundaries. The plates form in a similar way to mechanical twins but the shear processes lead to changes in crystal structure as well as crystallographic orientation.

Subjects

alloy | carbon | iron | martensite | metal | metastable | nickel | quenching | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Pearlitic malleable cast iron

Description

A cast iron with a relatively low carbon content. The sample has been normalised at 900 C for 72 hours in order to refine the grain size. The microstructure consists of pearlite with graphite.

Subjects

alloy | carbon | cast iron | iron | metal | normalising | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Kevlar fibre composite shear surface

Description

This is an image of the shear surface in a failed composite beam. 'Hackles' of matrix are clearly visible where shear has occurred within the matrix and it is also clear that shear has occurred across the fibre/matrix interface. The fibres are for the most part totally unscathed, though some mis-aligned fibres have become caught between the shear surfaces and 'fibrillated' by rolling and bending actions. It may be that this failure mechanism has been partly inhibited by poor fibre alignment since some off-axis fibres will reinforce the matrix in shear. It will have been promoted, however, by the extensive longitudinal voids.

Subjects

alignment | composite material | epoxy | fibre | fibrillation | fracture | hackle region | Kevlar | liquid crystalline polymer (LCP) | lyotropic | polymer | polymer composite | reinforcement | shear | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Fundamentals of Materials Science: Materials for Nuclear Power Generation

Description

This set of animations provides better understanding of the materials used in nuclear power generation. From TLP: Materials for Nuclear Power Generation

Subjects

nuclear | reactor | power | cross-section | displacement spike | dislocation loop | moderator | DoITPoMS | University of Cambridge | animation | corematerials | ukoer

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Fe, Ni 30, C 0.3 (wt%), quenched - martensite plates

Description

This sample was quenched to -80 C to give a metastable martensitic microstructure. The martensite plates show a lenticular morphology as the material attempts to shear as it transforms but is unable to open up voids at the grain boundaries. The plates form in a similar way to mechanical twins but the shear processes lead to changes in crystal structure as well as crystallographic orientation.

Subjects

alloy | carbon | iron | martensite | metal | metastable | nickel | quenching | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Pearlitic malleable cast iron

Description

A cast iron with a relatively low carbon content. The sample has been normalised at 900 C for 72 hours in order to refine the grain size. The microstructure consists of pearlite with graphite.

Subjects

alloy | carbon | cast iron | iron | metal | normalising | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Space-filling fire-resistant composite Barrikade (R)

Description

The concertina-like structure of the exfoliated vermiculite particles is clear. This configuration is set by the binder during the initial cure. This is then followed by a moulding operation and secondary, inter-particulate binding.

Subjects

Barrikade | composite material | edible | filler | fire resistant | thermal | vermiculite | ZnO | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Techniques for Studying Materials: Examination of an Artefact

Description

This set of animations provides guidance in physically examining an artefact including vitrual examination of an artefact. From TLP: Examination of an Artefact

Subjects

artefact | manufactured article | component | examination | material | identification | polymer | metal | alloy | ceramic | composite | DoITPoMS | University of Cambridge | animation | corematerials | ukoer

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Al 95, Cu 5 (wt%), microsegregation - cored dendrites

Description

This sample shows kappa-Al dendrites surrounded by a fine eutectic in which the two phases, kappa and ? (Al

Subjects

alloy | aluminium | copper | coring | dendrite | metal | microsegregation | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Pearlitic malleable cast iron

Description

A cast iron with a relatively low carbon content. The sample has been normalised at 900 C for 72 hours in order to refine the grain size. The microstructure consists of pearlite with graphite.

Subjects

alloy | carbon | cast iron | iron | metal | normalising | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Inter-particle bond in the fire-resistant composite Barrikade (R)

Description

This cross-section shows a typical bond, made between the two expanded vermiculite particles by the water soluble glass (sodium silicate) which is used as a binder. The flow of the binder towards such necks is driven by surface tension.

Subjects

Barrikade | composite material | edible | filler | fire resistant | thermal | vermiculite | ZnO | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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Techniques for Studying Materials: Atomic Force Microscopy

Description

This set of animations provides understanding of what Atomic Force Microscopy is and how it is used. From TLP: Atomic Force Microscopy

Subjects

afm | atomic force microscopy | surface morphology | cantilever deflection | contact | mode | tapping | artefact | nanotechnology | lateral force imaging | DoITPoMS | University of Cambridge | animation | corematerials | ukoer

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Al 95, Cu 5 (wt%), microsegregation - cored dendrites

Description

This sample shows kappa-Al dendrites surrounded by a fine eutectic in which the two phases, kappa and ? (Al

Subjects

alloy | aluminium | copper | coring | dendrite | metal | microsegregation | DoITPoMS | University of Cambridge | micrograph | corematerials | ukoer

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