Many of the copper -tin alloys phosphorus is added. Phosphorus is a strong deoxidiser, increasing fluidity and producing an alloy with increased tensile strength and wear resistance. A vertical section through Cu-Sn-P diagram at 5% tin. Phosphorus is present as copper phosphide Cu3P which forms by a eutectic reaction, appearing in the microstructure as a skeleton-like structure with the a+ d eutectoid. Cast phosphor bronzes containing up to 13 wt% tin and up to 1.0wt% phosphorus are used mainly for heavy -duty bearing where low coefficient of friction and high strength and toughness are required.