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In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure , and tend to decrease the electrical and thermal conductivity of the material.
Stress corrosion cracking processes associated with chemical dissolution along grain boundaries; Cyclic loading conditions; When the material has an insufficient number of independent slip systems to accommodate plastic deformation between contiguous grains. This is also known as intercrystalline fracture or grain-boundary separation. More ...
This sort of partitioning of solute atoms between the grain boundary and the lattice was predicted by McLean in 1957. [3] Non-equilibrium segregation, first theorized by Westbrook in 1964, [4] occurs as a result of solutes coupling to vacancies which are moving to grain boundary sources or sinks during quenching or application of stress. It can ...
Initial grain size affects the critical temperature. Grain boundaries are good sites for nuclei to form. Since an increase in grain size results in fewer boundaries this results in a decrease in the nucleation rate and hence an increase in the recrystallization temperature; Deformation affects the final grain size. Increasing the deformation ...
The fracture may change directions somewhat when entering a new grain in order to follow the new lattice orientation of that grain but this is a less severe direction change then would be required to follow the grain boundary. This results in a fairly smooth looking fracture with fewer sharp edges than one that follows the grain boundaries. [2]
A grain boundary is a single-phase interface, with crystals on each side of the boundary being identical except in orientation. The term "crystallite boundary" is sometimes, though rarely, used. Grain boundary areas contain those atoms that have been perturbed from their original lattice sites, dislocations , and impurities that have migrated ...
Grain boundary sliding (GBS) is a material deformation mechanism where grains slide against each other. This occurs in polycrystalline material under external stress at high homologous temperature (above ~0.4 [1]) and low strain rate and is intertwined with creep.
For homogeneous nucleation the nucleus is approximated by a sphere, but as we can see in the schematic of macroscopic droplets to the right, droplets on surfaces are not complete spheres and so the area of the interface between the droplet and the surrounding fluid is less than a sphere's . This reduction in surface area of the nucleus reduces ...