What is cryogenic temperature and Cryogenics?

A Temperature below -150°C or -238°F or around 123 K, in which a number of physical phenomena start to change rapidly from the room temperature characteristics. And Cryogenics is the science which deals with the study of achieving cryogenic temperatures and their effect on materials.

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What is Diffusion in Solids?

Diffusion is the process of movement of atoms from high concentration to low concentration in a material. Adolf Fick first discussed the molecular diffusion in binary components. Fick’s first law of diffusion for a binary mixture depends on flux, diffusion velocity, molar concentration, and temperature gradient. In the diffusion process, atoms change their original positions relative to the adjacent atom due to gradients. The gradient can be a concentration gradient, magnetic gradient, temperature gradient or stress gradient. Diffusion mechanisms involve vacancy diffusion, interstitial diffusion, substitutional diffusion, self-interstitial, self-diffusion, etc. Diffusion process can be either steady-state or non-steady-state process, which depends on flux i.e. the net number of atoms crossing a unit area per unit time in a particular direction. Some important factors that influence diffusion are diffusing material, temperature, crystal lattice, defects, etc.

What is Hydrogen embrittlement ?

Hydrogen embrittlement is an undesirable process resulting loss of ductility of metal, decrease of the toughness and reduction of load-bearing capability occurs due to the absorption of hydrogen atoms by the metal. So that there is crack formation in metal component and fracture at lower stresses conditions. There are mainly two types of Hydrogen embrittlement. The first one is internal hydrogen embrittlement, It occurs when the hydrogen dissolved in molten metal which becomes supersaturated with hydrogen immediately after solidification. And the second type is environmental hydrogen embrittlement, which results from by hydrogen absorption by the solid metal. This condition can occur during high-temperature thermal treatment & during electroplating, during corrosion reactions, during cathodic protection, operating hydrogen in high-pressure conditions etc.

What is Sensitization?

Sensitization means precipitation of carbides present at the grain boundaries in alloy and causing the alloy to be susceptible to intergranular corrosion. Intergranular corrosion is caused by the segregation of impurities and precipitates at the grain boundaries or by enrichment or depletion in the grain boundary. Sensitization in aluminum composites is an serious problem which is identified by the gradual formation and growth of beta phase Mg 2 Al 3 at grain boundaries, which increases the susceptibility of alloys to intergranular corrosion (IGC) and intergranular stress-corrosion cracking (IGSCC)

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