Specimen Preparation Techniques of Materials for ......Specimen Preparation Techniques of Materials...
Transcript of Specimen Preparation Techniques of Materials for ......Specimen Preparation Techniques of Materials...
Specimen Preparation Techniques of Materials
for Microstructural Analysis
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看真相不要看假相
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Reference
MetallographyMaterialography
• Metallography: the study of the microstructure of metals
– Can also be used to examine ceramics(ceramography岩相), polymers(plastography) and semiconductors
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The aim of material preparation:to reveal the true structure of the sample
• Specimen preparation quality is the determining factor.
• The classic computer adage, “garbage in =garbage out.”
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Gray Cast Iron Cu-10.5%SThe dendrites in aluminum alloy
Applications
Applications
IntergratedChip
The addition of fibber improves the strength of tennis racket
Heat-resistant Ceramic
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Sectioning 取样
Preparation 制样
Etching 浸蚀
Observation
Sectioning
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The specimens selected for preparation must be representative
Saw
Hammer
ViseClamp
Sectioning
Electric Spark Cutting
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Damage of Sectioning
10Cutting damage of an annealed titanium specime
Recast layer after spark cuttingAISI P20
• Precautions: Avoid alternation of the microstructure in the area of interest.
Sectioning
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Section
Preparation
Etching
Observation
Preparing metallographic specimens
• Objective: Remove the damaged layer to give a smooth surface
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Mounting (optional)• Hot Mounting• Cold
Mounting• Clamping
Grinding
Polishing• Mechanical
Polishing• electrolytic
polishing
Mounting
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Mounting
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Mounting
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Marking of specimens
• Engraving
• Stamping a code in the specimen
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Mounting (optional)• Hot Mounting• Cold
Mounting• Clamping
Grinding
Polishing• Mechanical
Polishing• electrolytic
polishing
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Grinding
The specimen is successively ground with finer and finer abrasive paper
The common grinding abrasives : SiC
Abrasive Paper
Larger the number, finer the abrasive particle
Cross Section of the Sample
Manual “Hand” Grinding
Grinding in one direction is usually better for maintaining flatness than grinding in both directions
Tips
• To protect your hand, round the sharp corner of the sample at the beginning
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Grinding-checking method
Grinding on the Rotating Disc attached with the SiC paper
Wet grinding minimizes specimen heating, prevents the abrasive from becoming loaded with metal removed from the specimen
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Mounting (optional)• Hot Mounting• Cold
Mounting• Clamping
Grinding
Polishing• Mechanical
Polishing• electrolytic
polishing
Mechanical Polishing
• To produce a deformation-free surface that is flat, scratch free, and mirror-like in appearance
• Carried out on polishing clothes with fine abrasive particles(eg: Al2O3, SiO2, Diamond, etc grain size 10~0.05 µm)
Polishing Particles smoothing the surface of the specimen
Manual “Hand” Polishing
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Specimen under LOM
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Washing and Drying
• After polishing, the specimen iswashed by running water, then rinsed withethanol, and dried in a stream of warm air
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Section
Preparation
Etching
Observation
Etching
• Chemical• Electrolytical• Special method
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selective corrosion
Etching
Commonly Used Etchants for Metals and Alloys
Composition CommentsNital 90-99 ethanol ,
1-10 mLHNO3
Most common etchant for Fe, and steels, cast ironUse by immersion or swabbing of sample for up to about 60 seconds.
Keller’s reagent
95 mL water 2.5 mL HNO3 1.5 mL HCI 1.0 mL HF very popular for Al and Al alloys.
Immerse sample 10-20 seconds, wash in warm water
90-100 mLwater 0.1-10 mL HF
General for Al alloys. Attacks FeAl3, other constituents outlined. The 0.5% concentration of HF is very popular
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Electrolytic Polishing/Etching)
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Simplified Procedure
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The Science Behind Materials Preparation——————
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Reference
AutomaticGrinder/Polisher
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A high efficiency with a higher degree of quality