An alloy is a mixture of metals or a mixture of a metal and another substance. Bronze is an alloy of copper and tin. steel is an alloy of iron and carbon. Stainless Steel is an alloy of steel,nickel and chromium.One familiar alloy is silver combined with the liquid metal mercury,which forms the amalgam of tooth fillings. Titanium-Steel alloy are used for their lightness and strength in planes and spacecrafts. Nickel-cobalt "super alloys" are sued in jet-engine turbine blades to withstand temperatures of over 1,000 C.At the other end of the scale, alloys of metals such as lead. Bismuth and cadmium melt at temperatures as low as 50 C and are used in fire alarms.