Alcan International Limited

David J Field

Ernest P Butler

Anthony J Bryant

Katherine-Ann Bassett

An extrusion ingot of an Al-Mg-Si alloy, has substantially all the Mg present in the form of particles having an average diameter of at least 0.1 microns of beta'-phase Mg.sub.2 Si in the substantial absence of bet-phase Mg.sub.2 Si. The ingot may be made by casting an ingot of the alloy, homogenizing the ingot, cooling the homogenized ingot to a holding temperature of 250.degree. C. to 425.degree. C. at a cooling rate of at least 400.degree. C./h, holding the ingot for 0.25 to 3 hours, and cooling. The ingot has improved extrusion properties.

Al-Mg-Si extrusion alloy

An extrusion ingot of an Al-Mg-Si alloy, has substantially all the Mg present in the form of particles having an average diameter of at least 0.1 microns of beta'-phase Mg.sub.2 Si in the substantial absence of beta-phase Mg.sub.2 Si. The ingot may be made by casting an ingot of the alloy, homogenising the ingot, cooling the homogenised ingot to a holding temperature of 250.degree. C. to 425.degree. C. at a cooling rate of at least 400.degree. C./h, holding the ingot for 0.25 to 3 hours, and cooling. The ingot has improved extrusion properties.

Al-Mg-Si extrusion alloy and method

The heat treatment of aluminium alloys having a lithium content in excess of 0.5% is carried out in an atmosphere of carbon dioxide and water vapor, the partial pressure of water vapor being at least 4 torr and more usually 10-50 torr.

Heat treatment of aluminium alloys containing lithium

Aluminum alloys containing lithium and copper and/or magnesium as principal alloying constituents are homogenized at 530.degree. C. or above to take into solution as-cast intermetallic phases which do not fully go into solution at conventional homogenization temperatures for this class of alloy. Preferably the alloy ingots are slowly heated at rates not exceeding 50.degree. C./hour up to a final homogenization temperature in the region of 550.degree.-560.degree. C. and are then allowed to cool without prolonged holding at temperature.

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Tean, United Kingdom

David J Field