abstract
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The use of AA 5754 Al-Mg alloy for automotive applications is limited by its rapid shear failure process, due to shear banding. This failure mechanism is further complicated by the presence of inhomogeneous plastic deformation, so-called Portevin-Le Chatelier (PLC) effect, during deformation. Therefore, the purpose of this study was primarily to investigate the impact of Portevin-Le Chatelier (PLC) banding towards shear banding in this commercial alloy. The second objective was to study the PLC banding as a function of prior deformation under positive strain rate sensitivity condition.
The experimental work involved pre-straining experiments coupled with a non-contact strain measurement technique. Pre-straining experiments were carried out by deforming the sample at 223 K, at which the PLC effect is significantly suppressed, up to a prescribed amount of true strain prior to room temperature testing. A non-contact strain measurement technique, based on digital image correlation (DIC), was utilized in order to observe PLC band behavior during tensile tests at room temperature and subsequently to measure the amount of plastic strain carried within the band.
The results showed the appearance of random nucleation deformation bands, associated with type B PLC banding, with short distance propagation during constant strain rate tensile test at room temperature. A change in the nature of PLC banding, marked by distinct band propagation, was observed once a critical amount of pre-strain is given. However, there is no evidence of a relationship between two existing phenomena, PLC banding and shear banding, in this alloy.