Tuesday, February 9, 2010

Grain Structure of Pure Metal and Alloy

Cristalize Structure of Pure Metal and Alloy

Pure Metals
The metal atoms are freely mobile in the liquid state. Iron or Fe is a pure metal when change to substance the name change become steel. When the melt freezes, a change point is observed, at which the temperature remains constant for a time in this period, the crystallization of the metal takes place, beginning from the so-called nuclear of crystallization (impurities, for instance). Metal atoms deposit in layers, binding forces become effective and crystallize begin to form. Each crystallize collides with each other, so that the continuous rows of atoms break abruptly. They continue to run into neighboring thus change from grain to grain, giving rise to a crystallize structure. The boundaries inside the structure are known as grain boundaries.

The freezing point of a metal is changed by alloying. It is dependent on the alloying ratio. The freezing curves of two nickel-copper alloys start at about 1250 oC.

In the melt, the individual atoms of the component metals are freely mixed. When the melt begins to freeze, the atoms of the alloying metals become nuclei of crystallization, from which the process of crystallization begins. Two lattice structures can result from this.

Cristal mixture:
The component of the alloy are each from their own crystallize. This results in a heterogeneous structure, in which dissimilar crystallize exist side by side.

Mixed Crystals (solid solutions):
The component of the alloy form a common lattice structure when this happens, each crystallize contains atoms of the different metals. These are then referred to as mixed crystals. The structure is homogeneous.

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