| 摘要 |
Aluminium alloy containing 0,5 - 2,5 % by weight on alloying mixture of Magnesium and Silicon, the molar ratio of Mg / Si lying between 0,70 and 1,2 5, an additional amount of Si equal to approximately 1/3 of the amount of Fe, M n and Cr present in the alloy, and the rest being made up of aluminium, unavoidable impurities and other alloying agents, which alloy after cooling has been submitted to homogenising, preheating before extrusion, extrusion a nd ageing, which ageing takes place at temperatures between 160 and 220 ~C. The ageing after cooling of the extruded product is performed as a dual rate ageing operation including a first stage in which the extrusion is heated wi th a heating rate above 30~C/hour to a temperature between 100 - 170 ~C, a seco nd stage in which the extrusion is heated with a heating rate between 5 and 50 ~C/hour to the final hold temperature between 160 and 220 ~C and in that the total ageing cycle is performed in a time between 3 and 24 hours.
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