Aluminium Cast Alloys

Aluminium alloys the cast by any one of the following processes.

Sand Casting is the simplest and most versatile process small castings, complex castings with intricate cores, large castings and structural castings are produced by sand casting with equal case.

In permanent mould casting a metallic mould is used which may be gravity6 filled or rotated for centrifugal action. The castings from permanent mould are fine grained as compared to sand cast products. In die casting maximum rate of production is achieved. The molten metal is forced into die which is split but sufficiently strong to withstand pressure. One important characteristic of die casting is close tolerance in parts. Fine grained structure and automation of process are other advantages.

Aluminium casting alloys need such element for alloying which will not only impart mechanical strength but will also increase fluidity and feeding ability. Therefore their chemical composition must differ from wrought alloys. Silicon is the most preferred alloying element in aluminium cast alloys for its improves fluidity and feeding ability as well as its mechanical strength. Normal silicon content varies between 5 to 12%. Magnesium in the range of 0.3 to 1% provides strength mainly through precipitation. Mg, Zn, Sn, Ti are also added sometimes.