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

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

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Engineering Materials
Chromium in steel

Gives ductility, toughness, tensile strength and anti-corrosion properties
Improves cutting ability and reduces hardenability
Refines grain size and produces less tendency to carburisation, improves corrosion and heat resistant properties
Improves wear resistance, cutting ability and toughness

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