High-Temperature Fatigue of Deep Rolled Aluminium Alloy AA6110-T6

Abstract

The precipitation-hardened aluminium wrought alloy AA6110-T6 (Al-Mg-Si-Cu) was mechanically surface treated (deep rolled) at room temperature. The cyclic deformation behavior and s/n-curves of deep rolled AA6110-T6 have been investigated by stress-controlled fatigue tests at room and elevated temperatures up to 250°C and compared to the polished condition as a reference. The effect of deep rolling on fatigue lifetime under high-loading and/or elevatedtemperature conditions will be discussed. The stability of near-surface residual stresses as well as work-hardening states (FWHM-values) was investigated by X-ray diffraction methods. Residual stress- and FWHM-depth-profiles before and after fatigue tests at elevated temperature are presented. It was found that the investigated AA6110-T6 aluminium alloy shows cyclic softening during stress controlled fatigue tests at room and elevated temperatures. Below a certain stress amplitude at a given temperature, deep rolling can enhance the fatigue lifetime of AA6110-T6 as compared to the untreated state through cyclically stable near-surface work hardening as indicated by stable FWHM values. From the s/n data of deep rolled and polished AA6110-T6, an effective boundary line for the deep rolling treatment in a stress amplitude-temperature diagram can be established.