Phosphor bronze

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An acoustic guitar string wrapped in phosphor bronze

Phosphor bronze is an alloy of copper with 3.5 to 10% of tin and a significant phosphorus content of up to 1%. The phosphorus is added as deoxidizing agent during melting. These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain. The phosphorus also improves the fluidity of the molten metal and thereby improves the castability, and improves mechanical properties by cleaning up the grain boundaries.

Further increasing the phosphorus content leads to formation of a very hard compound Cu3P (copper phosphide), resulting in a brittle form of phosphor bronze, which has a narrow range of applications.

Phosphor bronze is used for springs, bolts and various other items used in situations where resistance to fatigue, wear and chemical corrosion are required e.g. ship's propellors in a marine environment. Phosphor bronze is used in some metal wind instruments (e.g. the A992 alto saxophone manufactured by Yanagisawa[1]) instead of brass. Phosphor bronze is claimed to give wind instruments a "darker", more complex sound than the usual brass alloys. It is sometimes used to manufacture cymbals and acoustic instrument strings for acoustic guitars, mandolins and violins etc.

This alloy is also used as the metal component of some dental bridges. The phosphor-bronze alloy can also be used in electrical circuits due to its low resistance and high conductivity.

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