Papers by Keyword: AA7010

Abstract: The influence of Sc addition on the high temperature compressive strength of a commercial alloy 7010 (hereafter termed base alloy) has been examined. The base alloy, and the base alloy with 0.23 wt% Sc were cast, homogenized and subjected to compression tests at temperatures ranging from 300 to 450oC and strain rates of 10-3, 10-2, 10-1 and 1 sec-1. It is shown that Sc addition to the base alloy increases the compressive flow stress under these deformation conditions. The increase in peak flow stress is nearly 3-6 times the peak flow stress of the base alloy at temperatures 300-350oC over the strain rate range investigated. Whilst, at temperatures ³ 400oC, the flow stresses decrease significantly irrespective of the strain rate used. Transmission electron microscopy (TEM) revealed that a combination of (1) increased nucleation frequency of dispersoids, (2) evolution of smaller subgrain size, and (3) refinement of alloy phases in the Al-Zn-Mg-Cu system contribute to superior strengthening in the alloy containing Sc. Whilst, it is primarily a combination of coarsening and instability of the alloy phases in the Al-Zn-Mg-Cu system that dramatically reduces the flow stresses in both the alloys at temperatures ³ 400oC.

Abstract: The tensile strength, proof strength, hardness and electrical conductivity of Al alloy 7010 under different temper and ageing conditions were investigated with the aim to correlate strength with hardness and electrical conductivity so that the strength of the alloy can be determined nondestructively. Following the solutionising treatment, continuous age hardening was performed on a series of test coupons, taken from a large plate, to produce a wide range of precipitation hardening conditions, which gave rise to progressive variations of strength, hardness and conductivity. The relationship between strength and hardness was found to be reasonably linear, whereas the relationship between hardness and strength with electrical conductivity was non-linear. The ageing conditions and therefore the mechanical properties of the components can be predicted more accurately by the simultaneous combination of hardness and conductivity values.

Abstract: The corrosion susceptibility of friction stir welds in AA2024-T351 was found to vary with the weld processing parameters. Corrosion attack was investigated with in situ X-ray tomography, which showed how the penetration of corrosion into the interior of the structure varied with weld microstructure. The susceptibility to corrosion was related to the degree of overageing by comparing the corrosion behaviour to samples of the base alloy that had been aged at different temperatures. A systematic increase first in the anodic reactivity and then the cathodic reactivity of the overaged structures with temperature can be used to predict the location of the region of the weld with the highest susceptibility to corrosion. Similar investigations were made for a dissimilar weld between AA2024 and AA7010. Laser surface melting produces a thin homogeneous melted and rapidly solidified layer over the weld surface leading to a substantial improvement in corrosion resistance.