What is the grain boundary?
6 These lines are the boundaries of grains or lines that indicate the outer edge of the grain, crystal shapes that are formed as a material cooling from the liquid to the solid. Fixed substances that do not form grains are called amorphous, because the atoms that compose them do not organize into patterns as in crystalline solids. Before the liquid freezes, there are locations that are cooler than the rest of the liquid. From these places grows the grain out until it reaches another grain and stops. When all the liquid between the grains growing to each other froze into a solid substance, the boundaries of grain are formed as the growth stops.
Good examples of crystalline solids are metals and metal alloys. Metallurgists who are engaged in designing properties to metals, find that the grain boundaries are important when changing metals for different applications. The size and shape of the grain and their boundaries can be changed by heating and cooling metal at different speeds or cold grain, thus thinning them by compressing at the impact of heatthe rooms of the room.
To change the properties of the metal, it is exposed to sufficient heat so that the boundaries of the grain dissolve and reform, which is a process called annealing, where the slower cooling rate and the larger grain size have formed. When the metal part is stressed, the defects and holes in the atomic layers of the metal, called dislocations, move from the inside of the grain towards the boundary of the grain. If the metal is quickly cooled, the grains have less time to grow, reduce and dislocations encounter resistant borders and add strength to metal-male grain, for example, iron alloy. If the metal slowly cools down, the grains are larger because the dislocations have more time to move towards the border without causing the beginning of a larger hole or cracks. Large grains are seen in metals like copper and aluminum that are towing, easily expanding and slowing slowly.
grain boundary is an area on the surface of the grain that is more vulnerable to corrosive TueEye of chemical pollutants and forced crack growth that can lead to a failure or breaking of the metal part in time. Metals with small grains tend to be stronger than metals with larger grain, but have an increased opportunity to burst their borders that tend to be fragile and cause to break without warning. The cracks in the towing metal parts, such as aluminum alloys used in nozzles, with several dislocations at the grain boundaries, slowly grow. Over time, they can be safely monitored to predict how much life remains in the metal part or how much time it has before it can no longer work properly.