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Lecture

Effect of PLC band formation on the formability of a particle reinforced AA2017 alloy during Equal-Channel Angular Pressing

Wednesday (26.09.2018)
15:30 - 15:45 S1/01 - A3
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Formability of several aluminum alloys during severe plastic deformation is often limited by a pronounced strain localization, accompanied by material failure, that is caused by dynamic strain aging phenomena. In this work, we investigate the plastic deformation behavior of an age-hardenable aluminum alloy (AA2017) and of a particle reinforced metal matrix composite AA2017 (10 vol. % SiC) with a focus on serrated flow caused by the Portevin–Le Châtelier (PLC) effect. Tensile tests for both materials are performed in two different conditions: solid solution annealed (W) and naturally aged (T4). We observe pronounced serrated flow for both W-conditions, while both T4-conditions do not show distinct serrations. Compressive jump tests (with alternating strain rates) reveal a negative strain rate sensitivity for the W-condition – a strong indication for PLC-effects. Furthermore, we find that the onset of serrations is shifted to larger plastic strains and their amplitude is considerably reduced for lower testing temperatures (−60 °C, −196 °C). The propagation of the corresponding PLC bands in the W-condition is additionally characterized by digital image correlation 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. The results clearly demonstrate that PLC band formation is the main reason for a low formability of the investigated particle reinforced AA2017 during Equal-Channel Angular Pressing at room temperature. Consequently, reduced ECA-processing temperatures may promote homogeneous severe plastic deformation without material failure.

Speaker:
Christian Illgen
Chemnitz University of Technology
Additional Authors:
  • Dr. Markus Härtel
    Chemnitz University of Technology
  • Dr. Philipp Frint
    Chemnitz University of Technology
  • Prof. Dr. Martin F.-X. Wagner
    Chemnitz University of Technology