Alloy

Alloy is a mixture of two or more elements of which one is definitely a metal and all of them are mutually soluble in a liquid state which are fused above their melting point.

• Depending on dominant phase system, alloy systems are classified as:

Isomorphic (solid state/single phase)

Two metals which are completely soluble in both liquid and solid state. Homogenous mixture of two or more kinds of atoms(of metals) occurs in solid state. Ex: sterling silver(92.5% Ag & remaining Cu); Brass(64% Cu & 36% Zn); Gold alloys

Eutectic alloys

These are the Binary alloys which are completely soluble in liquid but shows limited solid solubility. Eutectic alloys melt at a temperature lower than fusion temperature of both the metals. They are inferior to Solid solutions, hence used in the soldering. They are brittle but hard and has poor tarnish and corrosion resistance. Ex: Ag-Cu system

Eutectic system phase diagram

Peritectic alloys

A peritectic reaction is a reaction where a solid phase and liquid phase will together form a second solid phase at a particular temperature and composition. These reactions are rather sluggish as the product phase will form at the boundary between the two reacting phases thus separating them, and slowing down any further reaction. Peritectics are not as common as eutectics and eutectiods, but do occur in some alloy systems. Ex: Fe-C system

Intermetallic system

They are intermediate phase in solid solutions. Their bonding between different types of atoms are partly ionic. They form a new phase with its own composition, crystal structure and properties. They are very hard and brittle and shows mechanical properties similar to ceramic materials. Ex: Ag-Sn in Cu rich amalgam alloy.

Alloy Resources
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