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Aluminium: I

Ident Pips, Pip Lines, Pip Marks, Pips

A marking on an extrusion (on a non-visible surface) placed there by the extrusion mill’s die to allow the mill to identify extrusions produced by that mill.

Indirect Extrusion, Backwards Extrusion

The extrusion method in which there is no relative movement between the billet and the container. This is accomplished by:- Either pushing the die held on the end of a long, hollow, stem through the billet. Or moving the billet and container together over the die, again held on the end of a long, hollow, stem. As there is no movement between the billet and container the friction, and hence extrusion loads, are reduced by up to 30% compared to direct extrusion and grain structures can be improved. The process is limited by the size, length and strength of the stem which holds the die.

Related terms: Direct Extrusion


A cast product that may be various shapes including slab, billet, bloom or more complex shapes. Produced by pouring liquid aluminium into a shaped mould and allowing it to cool.

Integral Colour Anodising

Coloured surfaces developed either by anodising certain Aluminium alloys and/or by using special organic electrolytes that produce colours during anodising.

Internal Stress

Stresses within a work-piece caused by previous treatments, e.g. casting, thermal treatment or fabrication.

Isothermal Quenching

A procedure in which the work piece is quenched, and held for some time, in a fluid which is held at a constant temperature between the solution treatment temperature and room temperature. This permits precipitation hardening.

Izod Test, Impact Test, Charpy Test, Fracture Test

A test in which the test piece is notched and broken. The fracture surface examined to assess grain structure and freedom from defects. Also used to determine toughness, often at varying temperatures to establish at what reduced temperature the material becomes brittle.