Search results
Results From The WOW.Com Content Network
As grain size decreases, the surface area to volume ratio of the grain increases, allowing more buildup of dislocations at the grain edge. Since it requires much energy to move dislocations to another grain, these dislocations build up along the boundary, and increase the yield stress of the material.
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.
This toughening becomes noticeable when there is a narrow size distribution of particles that are appropriately sized. Researchers typically accept the findings of Faber's analysis, which suggest that deflection effects in materials with roughly equiaxial grains may increase the fracture toughness by about twice the grain boundary value.
To heal this, grain-boundary sliding occurs. The diffusional creep rate and the grain boundary sliding rate must be balanced if there are no voids or cracks remaining. When grain-boundary sliding can not accommodate the incompatibility, grain-boundary voids are generated, which is related to the initiation of creep fracture.
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.
Grain boundary engineering involves manipulating the grain boundary structure and energy to enhance mechanical properties. By controlling the interfacial energy, it is possible to engineer materials with desirable grain boundary characteristics, such as increased interfacial area, higher grain boundary density, or specific grain boundary types ...
The absence of voids results from solid-state diffusive mass transfer, locally enhanced crystal plastic deformation, or solution and precipitation of a grain boundary fluid. [1] This mechanism operates at a low strain rate produced by neighbor switching. Grain boundary sliding is grain size- and temperature-dependent.
The surface energy of a liquid may be measured by stretching a liquid membrane (which increases the surface area and hence the surface energy). In that case, in order to increase the surface area of a mass of liquid by an amount, δA, a quantity of work, γ δA, is needed (where γ is the surface energy density of the liquid).