Why microstructures are different for different metals?
Answers
This is very different from ionic or covalent bonds, where electrons are held by one or two atoms. The metallic bond is therefore strong and uniform. Since electrons are attracted to many atoms, they have considerable mobility that allows for the good heat and electrical conductivity seen in metals
Answer:
Explanation:
When most molten metals solidify normally as the temperature falls below the melting point, they form crystalline structures, along with inclusion of other metallic or nonmetallic inclusions ( included within the crystal structure).
The crystals formed vary dependent on the metals and non metals that are present, along with the conditions of solidification such as temperature and cooling rate.
The crystalline structure of metals further changes as the metal is worked ( forged, hammered, rolled, extruded,etc) with the crystals being elongated, bent, fractured, and generally deformed plastically. Heating the deformed crystals to a high enough temperature causes those deformed crystals to recrystallize into “new” crystals, growing in a solidified state .
Metallurgists and metallographic technicians study this micro-structure using various techniques.
Metallography entails cutting samples of the metal, polishing a surface to a mirror finish and acid etching this surface to remove a very thin layer and reveal the intersections of the metallic crystals, their size, the inclusions, and to some extent the different types of crystals that are present.
Microscopes ( sometimes called metallographs) are used to examine and characterize the micro-structure looking close up at magnifications from 20 to 2000 times, and higher.
Electron microscopes use beams of energy with much smaller wavelengths than light to “ see” at very high magnifications as high as 10,000,000 X. Special types of electron microscopes are able to tell us the exact composition of the microstructure components.
Xray diffraction utilizes reflected and diffracted xrays to reveal information about the crystals, such as spacing between crystals elements, their structure relative to each other and the orientation of the crystalline planes relative to the sample taken.
This information teaches us the effects of working and heat treatments on the crystal size ( normally referred to as grain size), crystal growth, precipitation of insoluble components, and the relationship to other metal properties ( strength, hardness, ductility, brittleness, and others). We can study metal component failures, looking at the fracture surfaces, and anomalies in the microstucture to explain the failure.