Analysis of low cycle fatigue in AlMgSi aluminium alloys

Abstract

In this study low-cycle fatigue tests were performed in two AlMgSi aluminium alloys with different chemical composition, namely 6082-T6 and 6060-T6 alloys, using standard round specimens and tube specimens, respectively. The tests were undertaken in strain control with a strain ratio R e ¼ À1. The cyclic stress-strain curves were determined using one specimen for each imposed strain level. The low-cycle fatigue results are used for the characterisation of the cyclic plastic response and the fatigue live of the alloys. Moreover, the geometry of the hysteresis loops and the occurrence of Masing behaviour are also analysed. The observed behaviour is discussed in terms of the chemical composition of the alloys (Mg 2 Si hardening particles and Mn dispersoid content) and fracture mechanisms. Alloy 6060-T6 exhibits nearly ideal Masing behaviour, while alloy 6082-T6 presents significant deviations from the Masing model. The type of cyclic deformation behaviour in AlMgSi alloys seems to be influenced by the dispersoid phase.

Effect of Heat Treatment on Strain Life of Aluminum Alloy AA 6061

“…This convergence and divergence was agreed with tensile properties. The transition life (NT) is defined as the life where the total strain amplitude consists of equal elastic and plastic components, this imply, the life at which the elastic and plastic curves intersect (Haji, 2010;Borrego et al, 2004;Fenga et al 2010). The transition life was found to be the highest for O-condition, because it is being the less hardening behavior among other conditions.…”

“…To allow this prediction, complete information about the response and behavior of the material subjected to cyclic loading is necessary (Haji, 2010;Kwon, Song, Shin, & Kwun, 2010). Borrego, Abreu, Costa and Ferreira (2004) studied low-cycle fatigue of two AlMgSi aluminum alloys AA6082-T6 and AA6060-T6 alloys. They were concluded that AA6060-T6 exhibits nearly ideal Masing behavior, while alloy AA6082-T6 presents significant deviations from the Masing model.…”

Fatigue Behaviour of Welded Joints Made of 6061-T651 Aluminium Alloy

“…The monotonic strength and elastic properties of the 6061-T651 aluminium alloy are presented in Table 2. Table 2 also includes the properties obtained by Moreira et al (2008), for the 6061-T6 aluminium alloy, and by Borrego et al (2004), for the 6082-T6 aluminium alloy, for comparison purposes. In general, the three materials show comparable properties.…”

“…Table 3 summarizes the fatigue properties of the 6061-T651 aluminium alloy as well as the cyclic elastoplastic constants. Also, the properties obtained by Borrego et al (2004), for the 6062-T6 aluminium alloy, and Chung & Abel (1988), for the 6061-T6 aluminium alloy, are included for comparison purposes. The 6061-T651 aluminium alloy shows significantly higher fatigue ductility than the other aluminium alloys.…”

Determination of crack growth for 6082-T6 aluminium subjected to periodic single and block overloads and underloads using a two dimensional finite element model

“…The material properties used in the hardening rule, based on cyclic hardening, were obtained by the Ramberg Osgood relationship. The hardening coefficient H= 443 MPa and the hardening exponent n'= 0.064 were obtained from Borrego et al (41,42). The crack was grown in the numerical models by applying two load cycles and releasing the crack tip node just after the maximum load on the second load cycle.…”