Engineering Materials
Perminvar alloy having constant permeability is an alloy of

Copper, nickel and antimony
Nickel, copper and zinc
Iron, zinc and bismuth
Nickel, copper and iron

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Engineering Materials
Ductile cast iron

Contains 1.7 to 3.5% carbon in Free State and is obtained by the slow cooling of molten cast iron
Is also known as chilled cast iron and is obtained by cooling rapidly. It is almost unmachinable
Is produced by annealing process. It is soft, tough and easily machined metal
Is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material

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