Optical Metallography

Metallography is the study of the physical structure and components of metals, by using microscopy. Introduction

One of the most common materials characterization techniques, uses visible light to magnify structural features of interest. This discusses the use of optical methods to evaluate micro and macrostructure and relate it to process conditions and material behavior. It covers the steps involved in sample preparation, including sectioning, mounting, grinding, polishing, and etching, and presents several examples of macro and microanalysis on various metals and alloys. What is Optical metallography?

What is mounting? The purpose of mounting is to protect fragile or coated materials during preparation and to obtain perfect edge retention. Mounting is used when the protection of layers is imperative, and also it enables a safer and more convenient handling of small, sharp, or irregularly shaped specimens, for example. Mounting Facilitates handling of the specimen. A procedure that does not damage the specimen should be selected. Because large specimens are generally more difficult to prepare than small ones, specimen size should be minimized

How to do that? 1.Circular cylinders 25 to 50 mm (1 to 2 in.) in diameter 2.EpoFix Resin (8 ml) 3.Hardener Resin (1 ml) 4.Injection 5.Cotton bud 6.Release agent 7.Double tape 8.Plastic measuring cup (beaker plastic) 9.Samples

Grinding Grinding is the first step of mechanical material removal Proper grinding removes damaged or deformed surface material, while limiting the amount of additional surface deformation. The goal is a plane surface with minimal damage that can easily be removed during polishing in the shortest possible time.

How to do that? SandpapersGranding Mechine Type of sandpapers: 1.No No No, No, No No. 2500

Polishing Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action Polishing MechinePolishing cloth In rough polishing, the cloth covering on a wheel is impregnated with a fine (often as small as 1 µm) diamond paste or a slurry of powdered Al 2 O3 in water, and the specimen is held against the rotating wheel.

Etching Etching is process that removes material from the surface. Etching Methods : 1.Wet Etching (Liquid, chemical solvent, chemical reaction) 2.Dry ecthing or plasma etching ( gas, physical bombardment)

How to do that? Aqua Regia (HN03+HCL+H2O) 1.Aqua regia 2. Petri Dish 3.Tweezers 4.Cotton 5.Water 6.Alcohol 7.Dryer 8.Timer 9.Sampel Tools and materials :

Macroanalysis Macrostructural characterization of metals and alloys is the detailed evaluation of large-scale inhomogeneities in composition, morphology, and/or density. M acrostructure of metallographically prepared sections removed from the component of interest is used to evaluate such structural parameters as: Flow lines in wrought products Solidification structures in cast products Weld characteristics, including depth of penetration, fusion- zone size and number of passes, size of heataffected zone and type and density of weld defects General size and distribution of large inclusions and stringers Fabrication defects, such as laps, cold welds, folds, and seams, in wrought products Gas and shrinkage porosity in cast products

Metallographic analysis

1100 ℃ 1 hr WQ 7 8 3

1100 ℃ 1 hr WQ 600 ℃ 24hr WQ 7 8 4

1100 ℃ 1 hr WQ 650 ℃ 24hr WQ 7 8 5

1100 ℃ 1 hr WQ 700 ℃ 24hr WQ 7 8 6

1100 ℃ 1 hr WQ 750 ℃ 24hr WQ 78 7

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