Powder metallurgy -or PM- is a highly developed, cost-effective method of manufacturing components from ferrous materials (such as iron, steel, and stainless steel) and non-ferrous materials (including aluminum). Made by mixing elemental or alloy powders and compacting the mixture in a die, the resultant shapes are then sintered in a controlled atmosphere furnace to bond the particles metallurgically. On average, powder metallurgy uses more than 97% of the starting raw material in the finished part. Typically, powder metallurgy parts require little, if any, secondary machining. This "net shape" feature of powder metallurgy makes it an extremely energy-efficient process.