1 introduction metallography-sent

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STEEL-CORD

TIRES

CARBON FIBRE REINFORCED PLASTIC

GLASS FIBRE REINFORCED PLASTIC

METALS MATRIX

COMPOSITES


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METALS


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Materials Process Design and Control LaboratoryCCOOR R N NEELLLL U N I V E R S I T Y

REPRESENTATION AT VARIOUS LENGTH SCALES

Length ScalesElectronic

Atomistic

P h y s i c s

C h e m i s t r y M a t e r i a l s

E n g i n e e r i n

g

Micro-

structural

Continuum

Average Properties:

Large-scale

statistical quantities

Lattice

Positions,

Interfacial

energies etc.Particle

position/

momentum,

potential

nm m mm m

Lower order

Descriptors (Grainsizes,ODF,OCF etc.)


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• The name metallography was initially used in the early 1700’s to signify the

description of metals and their properties.

• It was first used in its modern sense in 1892, that is, to define the study of the

internal structure of metals and alloys in relation to their physical, chemical

and mechanical properties.

• Thus it can be seen that its procedures permeate all aspects of the

understanding and development of metals and their alloys.

Moreover, these techniques are widely used, or at least readily adapted to the

study of engineering materials, although full use of this commonality has only

been achieved comparatively recently with the replacement of courses in

metallurgy by courses in materials science and engineering.


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METALLOGRAPHY1. QUALITATIVE METALLOGRAPHY

2. QUANTITATIVE METALLOGRAPHY


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1. QUALITATIVE METALLOGRAPHY

What is to be obtained ?• Present Phases

• Grain Orientation

• Type of Faults Cracks, Porosities,

Non-Metallic Inclusions;• Oxides, Silicates, Sulfides,

Alumina, Nitrides, Carbonitrides

• Particle Shape


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Non-Metallic Inclusions


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Non-Metallic Inclusions


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A micrograph of bronze revealing a cast dendritic structure

Macrostructures


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Microstructures


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What is to be obtained ?• Phase Quantities

•

Grain Size• Phase Distributions

• Particle Size

•

Particle Volume Fraction• Particle Distribution

• Particle Composition

2. QUANTITATIVE METALLOGRAPHY


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Grain Size Determination

• How to report an average grain size?

• Draw few random straight lines through the

micrograph.

• The grain boundaries intersecting each line arecounted.

• The average grain size is obtained by dividing

the total length of the lines by the number ofintersections taking into account the

magnification used to produce the micrograph.


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METALLURGICAL MICROSCOPES

OPTICAL MICROSCOPY,

SCANNING ELECTRON MICROSCOPY,,

TRANSMISSION ELECTRON MICROSCOPY


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Microscopic techniques

• Optical microscopy used toobtain an enlarged image ofa small object. In general, acompound microscope

consists of a light source, acondenser, an objective, andan ocular or eyepiece, whichcan be replaced by arecording device such as aphotoelectric tube or a

photographic plate. Theoptical microscope is limitedby the wavelengths of thelight used and by thematerials available formanufacturing the lenses.


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Optical Microscopes


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Image analyzing system


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Optical Microscope


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Metallurgical microscope with 10

to 2000 magnification and a

camera attachment


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1 introduction metallography-sent

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