ALUMINIUM BRONZE, the name originally given to an alloy containing 9o% copper and Io% aluminium. Later, alloys with smaller percentages of aluminium and also those containing, in addition, I %-4% of manganese and iron were included under the general term "aluminium bronzes." The maximum percentage of aluminium in industrial bronzes is I I %, as larger proportions entail excessive brittleness.
Aluminium bronzes are distinguished by their golden yellow colour, which has led to their extensive use for art-metal work. Mechanically they approach mild steel, being strong and ductile and lending themselves readily to rolling and forging. In fact the alloy containing I o% aluminium has been compared with o•3 5 % carbon Swedish Bessemer steel, by no means to the disadvantage of the former. When cast the io% alloy has the following prop erties: As in the case of steel, these properties may be greatly improved by suitable heat treatment.
Casting in sand offers some difficulties and sound castings are not easy to obtain. Casting in chills or by the centrifugal process yields excellent results, and great quantities of such castings are regularly produced. Machining is troublesome and special pre cautions are called for owing to its high strength and resistance to alternating stresses. The io% bronze has been used with great success for the worm wheels of motor cars, many thousands of tons of metal having been cast for this purpose. Aluminium also confers on copper the property of resisting furnace and other sul phurous gases, so that these bronzes have proved' themselves well adapted for utensils subjected to direct contact with flames. They have also been used with success to withstand attack by sea water and the acid waters found in some mines. Aluminum manganese bronzes possess well defined magnetic properties.
For structure and mechanical properties see 8th and 9th Report of Alloys Research Committee, Proceedings of the Institute of Mechanical Engineers (1907, p. 57; 191o, p. 119). (R. S.)