It varies according to the carbon content in steel. The quenching of steel from the upper critical point results in a fine grained structure, whereas slow cooling or quenching from a higher temperature yields a coarse grained structure.
The coarse grained steels are less tough and have greater tendency for distortion than those having a fine grain. A fine grained steel, in addition to being tougher, are more ductile and have less tendency to distort or crack during heat treatment.
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Note: this simple cubic lattice does not exist in nature - however, it is simple to see. A dislocation is simply a defect in the lattice structure in which a few ions in a layer are missing. This causes the neighbouring layers to be displaced slightly to minimise the strain from the defect.
You can also think of it as being an extra row of ions. There can be millions of dislocations in each cubic millimetre of a metal. When a force is applied to the metal, the dislocations move through the lattice structure see picture 1. This only needs to be a small force smaller than that needed to produce slip because very few bonds are being broken at any one time. You can see the grains in which the crystals have grown in different directions.
Crystal grains. Just like steel, aluminum alloys become weaker as the service temperature rises. But aluminum melts at only about 1, degrees, so it loses about half of its strength by the time it reaches degrees. If you bend anything harder than aluminum, you will need to anneal it by heating along the bend line. When aluminum gets hot, first it is malleable, then it gets brittle, and then it melts.
When you heat aluminum too close to the melting point and then try to bend it, the workpiece can crack or break. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Engineering How does grain size affect the properties of a metal? Ben Davis December 31, How does grain size affect the properties of a metal? How do you reduce the grain size of a metal? What is the Hall Petch effect?
Why is grain size important in metals? How does grain size affect toughness?
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