The nonferrous metals are used in pure form because of such superior properties as electrical and thermal conductivity, corrosion resistance, high melting temperature, and special electrical, optical, and chemical properties. When any pure metal is alloyed with other metals or nonmetals, some properties are significantly impaired, others are significantly improved, and still others are not greatly altered. Aluminum alloys can be wrought (rolled, gorged, extruded, or drawn) or cast by any of the casting methods, including die casting. Magnesium alloys may be cast (die, sand, permanent mold, or investment), forged, extruded, or flat rolled, but are usually die cast because of the low cost, high quality, and accuracy afforded for producing intricate shapes. Copper can be hardened and strengthened by cold working and solid-solution alloying with zinc, tin, aluminum, silicon, manganese, and nickel. Zinc as a structural material is used with alloying addition of aluminum to improve strength. The corrosion resistance and mechanical properties of titanium alloys compare favorably with those of austenitic stainless steel. The white metals are low-melting alloys in which lead, tin, or antimony predominate. The most important precious metals are platinum, gold, and silver.