Material used for construction of transformer core is usually

Wood is a non-magnetic material and would not be suitable for use in a transformer. Copper and aluminium are both good conductors of electricity, but they are not ferromagnetic and would not be suitable for use in a transformer core.

Silicon steel is a relatively inexpensive material that is easy to work with. It is also a durable material that can withstand the high temperatures and magnetic fields that are present in transformers.