Metallography and Sample Preparation

<p>They can be reheated and re-shaped. (A)</p> Signup and view all the answers

<p>They can accommodate multiple specimens in a sandwich form. (D)</p> Signup and view all the answers

<p>320 °C (D)</p> Signup and view all the answers

<p>Methyl Methacrylate (A), Polystyrene (C)</p> Signup and view all the answers

<p>17 MPa (B)</p> Signup and view all the answers

<p>Polyvinyl Formal (B)</p> Signup and view all the answers

<p>Opaque (C)</p> Signup and view all the answers

<p>160 °C (B)</p> Signup and view all the answers

<p>4200 psi (C)</p> Signup and view all the answers

<p>Polyvinylchloride (A)</p> Signup and view all the answers

<p>To facilitate automatic specimen preparation (A), To protect and preserve edge defects (D)</p> Signup and view all the answers

<p>Cutting (A)</p> Signup and view all the answers

<p>Damage to microstructure (C)</p> Signup and view all the answers

<p>It helps to fill voids in porous materials (D)</p> Signup and view all the answers

<p>The method should not injure the microstructure (D)</p> Signup and view all the answers

<p>By damaging the sample and altering its characteristics (A)</p> Signup and view all the answers

<p>To facilitate easier handling of awkward shapes (B), To provide a permanent identification for storage purposes (D)</p> Signup and view all the answers

<p>Slicing (C)</p> Signup and view all the answers

<p>To lessen the depth of deformed metal for subsequent polishing. (C)</p> Signup and view all the answers

<p>40 mesh through 150 mesh (D)</p> Signup and view all the answers

<p>45 to 90 degrees between successive grit sizes. (B)</p> Signup and view all the answers

<p>The size and uniformity of the scratches. (C)</p> Signup and view all the answers

<p>To maintain a flat surface and avoid convexity. (D)</p> Signup and view all the answers

<p>It can result in severe surface damage, which is removable by prolonged grinding. (D)</p> Signup and view all the answers

<p>Clean the specimen to prevent carryover of particles. (C)</p> Signup and view all the answers

<p>The polishing process will be less effective. (B)</p> Signup and view all the answers

<p>135-275 (B)</p> Signup and view all the answers

<p>Diallyl phthalate (B), Bakelite (C)</p> Signup and view all the answers

<p>100 mm² (D)</p> Signup and view all the answers

<p>3.5 × 10-5 μm/min (D)</p> Signup and view all the answers

<p>2.9 × 10-5 (A)</p> Signup and view all the answers

<p>140 °C (A)</p> Signup and view all the answers

<p>105 mm/min (D)</p> Signup and view all the answers

<p>Opaque (A)</p> Signup and view all the answers

<p>Observing and determining the microstructure of metals and alloys (B)</p> Signup and view all the answers

<p>Anodizing (B)</p> Signup and view all the answers

<p>Flat, free from scratches and pits (A)</p> Signup and view all the answers

<p>Breaking the specimen from a large mass of material (A)</p> Signup and view all the answers

<p>It often requires more than one sectioning operation (C)</p> Signup and view all the answers

<p>It reveals the true microstructure of the specimen (A)</p> Signup and view all the answers

<p>The structure of a prepared specimen as viewed under a microscope (B)</p> Signup and view all the answers

<p>To ensure high-resolution imaging during microstructural analysis (C)</p> Signup and view all the answers

The process of preparing a sample for analysis by cutting it into a specific shape and size.

Methods used to cut and shape a sample for microscopy.

A sectioning method that uses crushing forces to reduce sample size.

A sectioning method that involves cutting the sample with tools like knives, shears, or diamond saws.

A sectioning method that uses an abrasive wheel to cut through the sample.

The process of securing a specimen in a mounting medium to protect it during preparation and examination.

Mounting methods are used to protect specimens from damage and make them easier to handle during preparation.

The mounting medium should not damage the specimen's microstructure. Factors like heat and hardness should be considered.

The study of the internal structure of metals and alloys, including the arrangement of their components and phases.

The arrangement of the different components (phases) within a material, often seen under a microscope.

The process of preparing a metal sample for microscopic analysis, involving multiple steps to reveal the microstructure.

Cutting a metal sample to a suitable size for analysis, ensuring it represents the original material.

The process of grinding a metal sample to a smooth, flat surface.

The process of polishing a metal sample to a mirror-like finish, removing any scratches or imperfections that could obscure the microstructure.

The process of chemically treating a polished metal sample to reveal the microstructure by selectively etching different phases or components.

A well-prepared metallographic specimen should accurately represent the original sample, be free of surface flaws and imperfections, and be flat enough to be examined at high magnification.

A type of thermosetting plastic known for its high strength, good electrical insulation, and resistance to heat.

The temperature at which a material begins to soften and deform under a specified load.

A measure of how much a material expands or contracts with changes in temperature.

The rate at which a material wears away due to friction, measured in micrometers per mile.

The ease with which a material can be polished to a smooth finish.

The ability of a plastic to withstand the effects of chemicals, such as acids and alkalis.

A type of thermosetting plastic known for its high strength, good electrical insulation, and resistance to heat.

A type of plastic that can be repeatedly softened by heating and hardened by cooling.

The maximum pressure that a material can withstand before it deforms or breaks. This is crucial for determining the material's ability to handle stresses and loads.

A measure of how easily a material can be stretched or deformed before it breaks. Higher elongation indicates greater flexibility. This property is essential for applications requiring bending or stretching.

A material's ability to withstand the effects of acids and alkalis. This property indicates how resistant the material is to corrosive environments.

The temperature at which a material becomes brittle and loses its strength. This property is crucial for determining a material's suitability for low-temperature applications.

An important property that determines the type and amount of light a material can transmit. Transparent materials allow light to pass through clearly while opaque materials block light.

The temperature at which a material starts to decompose or break down. This property is important in identifying safe operating temperatures for the material.

A measure of how easily a material can absorb water. This property is essential for determining the material's suitability for applications in wet environments.

The mounting media, used to hold the specimen, should have a significantly different hardness or abrasion resistance compared to the specimen itself. This ensures proper polishing and sample preparation without damaging the edges of the specimen.

It is crucial that the mounting medium used is resistant to the chemicals used in polishing and etching processes, commonly done to reveal the microstructure of the specimen. The mounting material should not be affected by these chemicals, maintaining its structural integrity.

Clamps are a preferred method for securing thin metal sheets when preparing cross-sections for metallographic analysis. This method allows several specimens to be held together in a 'sandwich' form. The strength of the clamp should be at least as strong as the specimen it's holding.

This method involves embedding specimens in a mold using heat and pressure, using materials like bakelite or acrylic resin. Thermosetting resins, like bakelite, solidify permanently after heating, while thermoplastic resins, such as acrylic, soften upon heating and can be reused.

Cold mounting uses materials like polyesters, epoxides, and acrylics, which require minimal pressure and only slight heat, allowing for faster mounting of specimens compared to compression mounting. This is a preferred option for large volumes of samples.

Grinding is the process of abrading a specimen's surface using progressively finer abrasive grit sizes to reduce the depth of deformed metal.

Coarse abrasives are typically used for initial grinding and have grit sizes from 40 mesh to 150 mesh. Fine abrasives are used for subsequent grinding and have grit sizes from 180 mesh to 600 mesh.

Grinding aims to minimize mechanical surface damage, which is further removed during polishing.

To completely remove the previous grinding scratches, it's essential to change the direction of grinding by 45 to 90 degrees between each grit size.

The depth of deformed metal and scratch depth decreases as the abrasive particle size decreases.

Each grinding step should entirely remove the deformed metal created by the previous step to prevent carryover of damage.

Maintaining equal pressure on both sides of the specimen during manual grinding helps create a flat surface and avoid rocking motion.

Cleaning the specimen after each grinding step is crucial to prevent carryover of abrasive particles to the next step.