A defect found in extruded products due to incorrect extrusion procedures at the mill.
Backwards Extrusion Indirect 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.
The resistance of a metal to plastic deformation usually by indentation using a diamond or a hardened steel ball.
There are various recognised hardness scales including Vickers (VPN), Brinell and Rockwell.
N.B. The empirical, but robust, relationship between hardness and tensile properties that applies in steels does not apply, and the steel tables must not be used for aluminium and its alloys. A less rigorous relationship has been established for some aluminium alloys but it is not widely used.
Buckle Ripple
The variation in flatness represented by alternate bulges and hollows along the length of a rolled product, the edges of which remain reasonably flat.
Busbars
Bar or section for use as a common junction between electrical circuits.