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Micrograph of a polycrystalline metal; grain boundaries evidenced by acid etching. Differently-oriented crystallites in a polycrystalline material. In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material.
e) micrograph of acid etched metal highlighting grain boundaries A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains .
Electron channelling contrast imaging (ECCI) is a scanning electron microscope (SEM) diffraction technique used in the study of defects in materials. These can be dislocations or stacking faults that are close to the surface of the sample, low angle grain boundaries or atomic steps.
Some maps describe grain orientation, boundary, and diffraction pattern (image) quality. Various statistical tools can measure the average misorientation, grain size, and crystallographic texture. From this dataset, numerous maps, charts and plots can be generated.
When cooling off it passes a phase boundary where kamacite is exsolved from taenite. Meteoric iron with less than about 6% nickel (hexahedrite) is completely changed to kamacite. Widmanstätten pattern, metallographic polished section. Iron and nickel form homogeneous alloys at temperatures below the melting point; these alloys are taenite. At ...
Metallography allows the metallurgist to study the microstructure of metals. A micrograph of bronze revealing a cast dendritic structure Al-Si microstructure. Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. [1]
The interlocking nature of acicular ferrite, together with its fine grain size (0.5 to 5 μm with aspect ratio from 3:1 to 10:1), provides maximum resistance to crack propagation by cleavage. Composition control of weld metal is often performed to maximise the volume fraction of acicular ferrite due to the toughness it imparts.
The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks and hardness microindentations. Most bulk mechanical, optical, thermal, electrical and magnetic properties are significantly affected by the microstructure. The fabrication method and process conditions are generally indicated by the microstructure.