Material Science - Short answer questions from AMIE exams

What is the main objective of normalizing as a heat treatment process?
In normalizing there is complete phase re-crystallization and the fine grain structure is obtained. It is a type of heat treatment applicable to ferrous metals only. In the normalizing process, the material is heated to an elevated temperature and after that, it is cool back by placing it in contact with air at room temperature. This process of cooling metal with air is called air quenching.

What is the maximum solubility of carbon in iron?
The maximum solubility of carbon in iron is 2 %.

How are resistivity and conductivity related?
The conductivity of reciprocal of resistivity and has units ohm-1 m-1

Why does the resistivity of copper increase due to the presence of solute atoms?
The solute atoms cause lattice distortion, these imperfections, cause irregularities in electric fields within the metal and decrease the mean free path thus reducing the mobility of electrons, thereby increasing the resistivity of metal.

What is the effect of the use of plasticizers on thermoplastic materials?
The plasticizer prevents crystallization producing non-crystalline solid. These provide flexibility, impart toughness, improve the flow of material and act as an internal lubricant.

What is the permeability of diamagnetic material?
The permeability of diamagnetic material is less than one.

What are the constituents of white metal bearing alloys?
The white metal bearing consists of Antimony, Copper, tin and lead typical examples are
  • Antimony 7.5 %, Cu 4.5 %, Pb 0.75 %, rest Tin
  • Antimony 10 %, Cu 0.5 %, Tin 0.5 %, Rest Lead
What is 18-4-1 high-speed steel?
Steel having 18 % tungsten, 4% chromium, 1% vanadium with 0.75 % carbon is called 18-4-1 high-speed steel.

Which alloying element is most important to make steel corrosion-resistant?
Chromium is the most important alloying element to make steel corrosion-resistant.

What is the carbon percentage in high-speed steel?
The carbon percentage in high-speed steel is about 0.75.


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