ALLOY: An alloy is a homogeneous mixture or solid solution of two or more metals. Alloys are used in various applications, where their properties are superior to those of the pure component.
EUTECTIC ALLOY: An alloy that melts and freezes at a single temperature that is lower than the melting points of the separate constituent metals or composition of the same metals in any different proportions.
SOLIDUS: Solidus is the temperature above which the alloy starts to melt. It is not necessary that the alloy will completely melt at its solidus.
LIQUIDUS: Liquidus is the minimum temperature at which all components of an alloy are in a liquid state. Below the liquidus the alloy will be partly or entirely solid.
CAPILLARY ACTION: Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity. During brazing due to capillary action, the brazing filler alloy flows into thin joint spaces. The alloy tends to flow towards the heated sections of the assembly, thus it is very important to heat the parts to be joined before adding the brazing filler alloy.
OXIDATION: During the brazing process, a chemical combination between the hot metal and oxygen in the air may occur, resulting in the formation of oxides on the base metals being joined. These oxides must be prevented from forming as they'll inhibit the brazing filler metal from wetting and bonding to the surfaces. Thus, it is very important to apply proper flux on the base metals before brazing.
FLUX: In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Proper fluxing is important when brazing because the flux absorbs oxides formed during heating and promotes the flow of filler metal. Flux residue must be removed after brazing for inspection of the joint and pressure testing.