Accelerated artificial ageing regimes of commercial aluminum alloys. I. Al-Cu-Mg alloys

The effects of temperature and exposure on the phase composition and morphology of hardener precipitates, strength and plasticity of commercial Al-Cu-Mg alloys were carried out. These results are submitted as TTT (time-temperature transformation) and TTP (time-temperature properties) diagrams for ageing. In Al-Cu-Mg alloys within a wide temperature range (160-260 degrees C) the structure of hardener precipitates is the same. The age hardening rate is determined by identical diffusion processes subjected to the Arrhenius equation. For this system short-term accelerated artificial ageing regimes with exposure of less than 10 min is possible for reception of high strength. Examples of such regimes used for thin sheets from D16 and 1161 alloys in commercial conditions on a continuous heat treatment line are given. For thicker products accelerated regimes depend on the heating duration determined by the type of thermal device, the modes of stacking products, their thickness and non-uniformity on thickness. The examples of the accelerated ageing regimes in commercial conditions for forgings from AK4-1 alloy (type of 2618 alloy) are presented. The comparison of the mechanical properties, damage tolerance, corrosion resistance, technological plasticity of the semiproducts processed by standard and accelerated ageing regimes is given. (C) 2000 Elsevier Science S.A. All rights reserved.