Brasses are alloys of copper and zinc. They may also contain small amounts of other alloying elements to impart advantageous properties. Brasses have high corrosion resistance and high tensile strength. They are also suited to fabrication by hot forging. Free machining grades of brass set the standard for machining, by which other metals are compared.
Brass Classes

Brasses are divided into two classes. The alpha alloys, with less than 37% zinc, and the alpha/beta alloys with 37-45% zinc. Alpha alloys are ductile and can be cold worked. Alpha/beta or duplex alloys have limited cold ductility and are harder and stronger. CZ121 is an alpha/beta alloy.
Alloy CZ114

Brass alloy CZ121 is used for machining. It has lead added to the composition to improve machinability. The lead remains insoluble in the microstructure of the brass and the soft particles act as chip breakers.