(a) Which two elements are alloyed to form a brass ?
(b) What are the differences (i) in composition, (ii) in uses, of an 'alpha' and an 'alpha-beta' brass ?
(a) A brass is essentially an alloy having major constituents as copper and zinc. Minor proportions of elements such as lead and tin may be included to promote special properties.
(b) An alpha brass is an alloy in which zinc does not exceed by 38%. This brass is ductile and, therefore, used for cold-rolled sheets, wire, tube and cold pressing. Cartridge brass contains 70% copper, 30% zinc and is a very suitable material for deep-drawing cartridge cases.
An alpha-beta brass is an alloy of copper and zinc containing zinc between about 38% and 47%. The appearance of the beta constituent is associated with increased strength at the expense of ductility. An alpha-beta brass does not lend itself to cold-working, but is readily hot-worked by rolling, extrusion and hot-pressing. It is readily machined, the machinability being even more improved by the addition of lead. A typical alpha-beta brass is Muntz metal (60% copper, 40% zinc), which is used for the production of low pressure water fittings by hot-pressing.