Portevin-Le Chatelier effect triggered by complex loading paths in an Al–Cu aluminium alloy

ABSTRACT

Serrated flow has been observed during non monotonic tensile tests of an Al–Cu aluminium alloy in the naturally aged state. The associated propagative localisation bands were observed by digital image correlation (DIC). In particular, the Portevin-Le Chatelier (PLC) effect and also Lüders bands were observed in interrupted tests during which the specimen was held for a length of time and also in tests with partial unloading followed by a holding time. Increasing strain rate jumps also triggered the PLC effect. These observations indicate the existence of the PLC effect in this material which was formerly considered insensitive to it at room temperature under monotonic loading conditions. There is no evidence of PLC serrations during constant strain rate tests. A strain ageing finite element model is used that captures the experimentally found PLC triggering effects.

KEYWORDS:

• Portevin-Le chatelier effect
• AA2139-T3 aluminium alloy
• stress relaxation
• strain path change
• strain rate sensitivity

Acknowledgments

The authors gratefully acknowledge Constellium C-TEC for materials supply. We would like to acknowledge Vladimir A. Esin of the Centre des Matériaux at Mines ParisTech for help with the DICTRA simulations and discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank ANR project, with reference ANR-11-BS09-0008, on "Analysis of fracture at low stress for partial funding of this work.