Abstract
The Portevin–Le Châtelier (PLC) effect often results in serrated plastic flow during tensile testing of aluminum alloys. Its magnitude and characteristics are often sensitive to a material’s heat treatment condition and to the applied strain rate and deformation temperature. In this study, we analyze the plastic deformation behavior of an age-hardenable Al-Cu alloy (AA2017) and of a particle reinforced AA2017 alloy (10 vol. % SiC) in two different conditions: solid solution annealed (W) and naturally aged (T4). For the W-condition of both materials, pronounced serrated flow is observed, while both T4-conditions do not show distinct serrations. It is also found that a reduction of the testing temperature (−60 °C, −196 °C) shifts the onset of serrations to larger plastic strains and additionally reduces their amplitude. Furthermore, compressive jump tests (with alternating strain rates) at room temperature confirm a negative strain rate sensitivity for the W-condition. The occurring PLC effect, as well as the propagation of the corresponding PLC bands in the W-condition, is finally characterized by digital image correlation (DIC) and by acoustic emission measurements during tensile testing. The formation of PLC bands in the reinforced material is accompanied by distinct stress drops as well as by perceptible acoustic emission, and the experimental results clearly show that only type A PLC bands occur during testing at room temperature (RT).
Highlights
Plastic instabilities, which occur in many age-hardenable aluminum alloys [1,2,3,4,5,6,7,8,9,10,11,12,13] within a certain regime of strain rates and testing temperatures, are often associated with the observation of repeated stress serrations in the stress–strain curves of tensile or compression tests
We study the influence of different heat treatments, deformation temperatures and applied strain rates on the magnitude of a potential Portevin–Le Châtelier (PLC) effect in a high-strength, age-hardenable Al-Cu alloy (AA2017), and in a particle reinforced AA2017 alloy (10 vol % SiC) in two different conditions
PLC effects are strongly influenced by the concentration of solute serrated flow (PLC effect) for both materials
Summary
Plastic instabilities, which occur in many age-hardenable aluminum alloys [1,2,3,4,5,6,7,8,9,10,11,12,13] within a certain regime of strain rates and testing temperatures, are often associated with the observation of repeated stress serrations in the stress–strain curves of tensile or compression tests. The so-called “jerky” or “serrated” flow is one of the most distinctive examples of plastic instability in dilute alloys It is commonly rationalized by the dynamic interactions between solute atoms and mobile dislocations, i.e., dynamic strain aging processes [1,3,4,5,6,9,11,12,14,15,16,17,18,19,20,21,22,23]. An occurrence of stress serrations in the plastic flow behavior as a result of dynamic strain aging processes is, usually referred to as the Portevin–Le Châtelier effect (PLC effect)
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