Investigation of PLC band nucleation in AA5754

Thermomechanical characterization of Portevin–Le Châtelier bands in AlMg3 (AA5754) and modeling based on a modified Estrin–McCormick approach

“…6e), a strong stress plateau is observed which is related to a strong Lüders band. This Lüders band nucleates with two deformation fronts, which propagate towards opposite sites of the specimen (see Feng et al, 2012). Halim et al (2007) found this type of stress plateau in each of their tensile tests on AA5754 sheet for various strain rates at room temperature.…”

“…8(e)-(h) for a similar time interval of Dt :¼ t 4 À t 1 ¼ 0:21 s. Since the agreement between experimental and simulated band positions at different times is quite good, we may conclude that the band velocity is predicted correctly in the simulation. As shown by Feng et al (2012), near t 3 , x y p 0 p 0 p 0 p 0 t 1 = 7.10 s t 2 = 7.17 s t 3 = 7.24 s t 4 = 7.31 s t 1 = 7.10 s t 2 = 7.17 s t 3 = 7.24 s t 4 = 7.31 s the band reaches the lower edge of specimen, the stress peaks, and band formation is complete. In the subsequent phase of pure longitudinal band propagation (between t 3 and t 4 ), the stress decreases.…”

“…On the other hand, digital image correlation (DIC) was employed (i.e., incremental correlation: see, e.g., Tong et al, 2005;Zavattieri et al, 2009a) for unpolished specimens. This method has been applied in previous works to SEM and IR images (Crostack et al, 2001;Feng et al, 2012;Tillmann et al, 2013) as well as to tomograms (Crostack et al, 2008;Fischer et al, 2013). Both methods are used to obtain IRR intensity-based images of the PLC band as a function of time during the tests.…”

“…1a and 3). An example of such nucleation from Feng et al (2012) is shown in Figs. 8a-d. Before reaching the lower edge (transverse propagation), the band starts to propagate in axial direction of the specimen (longitudinal propagation).…”

Forming performance of an as-quenched novel aluminum-lithium alloy

“…The defects distort the surrounding lattice and cause an increased stress concentration impeding the dislocation motion. With deformation, thinner bands are observed when plastic instabilities occur [17]. Since a single band is unable to carry the imposed strain rate, the phenomenon of multiple bands emerges as shown in Fig.…”