Please use words to explain the following How the grain size

Please use words to explain the following.

How the grain size of a crystalline material could be decreased materials exhibit creep at elevated temperatures under stress electronegativity determines the type of primary bond in ceramics the energy-distance curve between two atoms accounts for thermal expansion dislocations both weaken and strengthen materials temperature-time curves for precipitation reactions have a nose-shaped appearance alloys are always stronger than pure metals

Solution

a) Grain size is often determined by the rate at which the material cooled during forming. If you can melt the material and then cool it rapidly, that would create small grains.

If you can\'t do that then cold work can also reduce the grain size. This is akin to stressing the material (hammering, rolling, pressing etc.) well below it\'s recrystallization temperature.

b)creep is the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods

g)A pure metal has identical atoms arranged in regular layers. The layers slide over each other easily. Alloys are harder and stronger because the different-sized atoms of the mixed metals make the atomic layers less regular, so they cannot slide as easily.

e)

In simple terms, the crystal structure of metals means the atoms are in uniform layers. That means that the \'gaps\' between them are inline. This allow one layer to easily slide along the next. The more you work the metal, the more those gaps no longer line up, making it more difficult for the layers to slide along each other.
This is also the reason they add carbon to iron to make steel. The carbon locks the iron layers to each other, preventing them from moving.

Also dislocations can make the metals weak if the dislocations dont pile up(it means if the grain broundary density does not increase on applying a force.This is mainly because of low carbon.