50th Anniversary Article: The Origin and Management of Residual Stress in Heat‐treatable Aluminium Alloys

Abstract

The presence of macroscopic residual stresses in heat-treatable aluminium alloys can give rise to machining distortion, dimensional instability and increased susceptibility to in-service fatigue and stress corrosion cracking. This paper presents and reviews details about the residual stress magnitudes and distributions introduced into wrought aluminium alloys by the thermal operations associated with heat treatment. Experimental measurement data and the results of finite element analysis are presented and discussed. The available technologies by which residual stresses in aluminium alloys can be relieved are reviewed. The limitations of these techniques are described, and recommendations are made as to selecting the most appropriate technique to manage residual stresses. Opportunities for the future optimisation of these techniques are also presented.

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

“…However, it is not negligible as revealed by the 50 MPa difference between simulations with and without precipitation at the surface. Robinson et al (2014) measured ca. 180 MPa compressive stress at the surface of a 16 mm thick AA7010 block.…”

“…However, high thermal gradients through the thickness cause non-homogeneous plastic strain resulting in residual stresses (RS) after quenching. Robinson et al (2014) showed that surface RS measured by X-ray diffraction on AA7010 cold-water-quenched rectangular blocks increase when the thickness increases from 16 mm to 124 mm. Quenching is thus followed by a stress relief, as explained by Jeanmart and Bouvaist (1985), that reduces residual stresses by a factor of approximately 10 as shown by Boyer and Boivin (1985).…”

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

“…Thermal gradients decrease from the surface to the center and give rise to residual stresses (RS) [6]. 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 slower quench conditions (Q2-Q4) refers to cooling conditions that are typical between the surface and center of larger forgings [13,20]. The cooling conditions end at 100°C since large components are often quenched in boiling water to control RS [6]. Fig.…”

“…The mechanical properties are tailored by the age-hardening treatment, which also involves a quenching step. Thermal gradients decrease from the surface to the center and give rise to residual stresses (RS) [6]. The magnitude of the as-quenched RS can be very high and even exceed the as-quenched strength of the materials [6,7].…”