Quench induced residual stress prediction in heat treatable 7xxx aluminium alloy thick plates using Gleeble interrupted quench tests

Abstract

a b s t r a c tIn this paper, a simple but realistic approach is presented to predict the as-quenched residual stress distribution in thick 7xxx aluminium alloy plates. Instead of modelling precipitation that occurs during quenching, a thermo-mechanical model is used whose parameters are identified using a limited number of tensile tests achieved after representative interrupted cooling paths in a Gleeble machine. The material behaviour law accounts for recovery at high temperature in a simple way and neglects the Bauschinger effect as suggested by a dedicated experiment. The results of this simple approach are compared to residual stress measurements in plates of different thicknesses for two different 7xxx alloys, AA7449 and AA7040.

Characterisation of precipitation upon cooling of an AA2618 Al–Cu–Mg alloy

“…However, fast quenching cannot be achieved in the centre of large components, where the quenching rate can be more than one order of magnitude lower than at the surface. This results in: possible coarse precipitation of the S/S' phases which is detrimental to the final yield strength since it decreases the hardening potential by pumping solute elements during quenching, and usually unwanted residual stresses (RS) that depend on the cooling rate, and on the component size and shape but also, as shown in the case of AleZneMgeCu thick cold-water quenched plates [4], on the precipitation that forms during quenching.…”

Early cluster formation during rapid cooling of an Al–Cu–Mg alloy: In situ small-angle X-ray scattering

“…SAXS provides the means to collect information on the size and volume fraction of the precipitates that can then be directly compared to predictions of thermodynamic-based precipitation models [11,12]. These models can be coupled with macroscopic finite-element RS simulations to better predict the residual stress formation during the processing of industrial components [9,13] as part of through-process modeling.…”

“…The magnitude of the as-quenched RS can be very high and even exceed the as-quenched strength of the materials [6,7]. In the case of Al-Zn-Mg-Cu alloys, the high as-quenched RS are caused by the formation of fine hardening precipitates that form during quenching of large components and thereby increase the yield strength of the material [8,9].…”

“…The magnitude of the as-quenched RS can be very high and even exceed the as-quenched strength of the materials [6,7]. In the case of Al-Zn-Mg-Cu alloys, the high as-quenched RS are caused by the formation of fine hardening precipitates that form during quenching of large components and thereby increase the yield strength of the material [8,9].In order to predict the RS formation in industrial components during quench, the changes of the nanostructure during cooling conditions close to industrial practice needs to be characterized as they highly impact the yield strength and thus the internal stress generation. Further, the influence of excess vacancies on precipitation during cooling needs to be explored.…”

“…SAXS provides the means to collect information on the size and volume fraction of the precipitates that can then be directly compared to predictions of thermodynamic-based precipitation models [11,12]. These models can be coupled with macroscopic finite-element RS simulations to better predict the residual stress formation during the processing of industrial components [9,13] as part of through-process modeling.This work investigates the Cu-Mg cluster formation during cooling conditions close to industrial quenching in an Al-Cu-Mg alloy. In addition, a cooling profile with faster rates at high temperature is performed in order to investigate the influence of excess vacancies on the Cu-Mg cluster formation.…”