Engineering Materials
A material is known as allotropic or polymorphic if it

Exists in several crystal forms at different temperatures
Has its atoms distributed in a random pattern
Responds to heat treatment
Has a fixed structure under all conditions

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Engineering Materials
Grey cast iron

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

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