Effect of age hardening on the deformation behavior of an Mg-Y-Nd alloy: In-situ X-ray diffraction and crystal plasticity modeling

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:628

Article

Lentz, Martin¹  Klaus, Manuela²  Wagner, Michael¹  Fahrenson, Christoph³  Beyerlein, Irene J.⁴  Zecevic, Milovan⁵  Reimers, Walter¹  Knezevic, Marko⁵ 

[1] Tech Univ Berlin, Metall Werkstoffe, D-10587 Berlin, Germany

[2] Helmholtz Zentrum Berlin Mat & Energien, D-12489 Berlin, Germany

[3] Tech Univ Berlin, Zentraleinrichtung Elektronenmikroskopie, D-10623 Berlin, Germany

[4] Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA

[5] Univ New Hampshire, Dept Mech Engn, Durham, NH 03824 USA

关键词: Magnesium alloys;    Crystal plasticity;    In-situ diffraction;    Deformation behavior;    Texture;   

DOI  :  10.1016/j.msea.2015.01.069

来源: Elsevier

【 摘 要 】

The present study investigates the deformation behavior of an extruded Mg-Y-Nd (WE54) alloy in as-extruded and aged conditions. Via age-hardening at 250 degrees C for 16 and 500 h or annealing treatments at 400 degrees C for 24 h, precipitates are formed within the grains or at the grain boundaries. To characterize microstructural changes with the age-hardening conditions, we employ electron-backscattered diffraction, transmission electron microscopy, and optical microscopy. In the as-extruded material, we observed an uncommonly low activity of {10 (1) over bar2}< 10 (11) over bar > tension twinning in comparison with other Mg alloys. The tension twinning activity substantially increased after precipitation hardening and the accompanying reduction of alloying element concentration in solid solution. Consistent with the microstructural observations, the increase in twin activity clearly manifests in the compression flow curves. While the as-extruded and 16 h/250 degrees C samples exhibited a classical decreasing hardening rate throughout straining associated with crystallographic slip, the 500 h/250 degrees C and the 400 degrees C annealed sample featured a characteristic increase in the hardening rate associated with twinning. In order to determine the impact of the different heat treatments on the individual slip and twinning modes, in-situ energy-dispersive X-ray synchrotron diffraction experiments during loading and elasto-plastic self-consistent modeling were conducted. We find that plate-shape precipitates on the {10 (1) over bar0}(alpha), planes harden < a > basal slip more than the other slip systems, while the reduced solute concentration in the 500 h 250 degrees C and 24 h 400 degrees C samples results in a significant decrease in the critical resolved shear stress for {10 (1) over bar2}< 10 (11) over bar > tension twinning. (C) 2015 Elsevier B.V. All rights reserved.

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