A model for slip and twinning for extruded magnesium under cyclic loading

作者：Guillemer C^*; Clavel M; Cailletaud G

来源：Revue de Metallurgie-Cahiers d Informations Techniques, 2012, 109(6): 423-426.

DOI：10.1051/metal/2012031

• Magnesium
• dislocations
• twinning
• untwinning
• polycrystal
• crystal plasticity
• cyclic loadings

A model for slip and twinning for extruded magnesium under cyclic loading. The present study aims at determining and modeling the mechanical behavior of pure extruded magnesium, especially under cyclic straining at room temperature. For this purpose, tensile, compressive and cyclic tests are performed (small plastic strains are applied, respectively Delta epsilon(rho)/2 = 0.1% and 0.4% in cyclic tests). Deformation mechanisms (slip and twin systems) have been observed by Transmission Electronic Microscopy and the different critical resolved shear stress have been determined. Based on microscopic observations, a crystal-plasticity based constitutive model has been developed. The asymmetry between tensile and compressive loadings mainly results from the activation of hard slip systems in tension (such as %26lt; a %26gt; pyramidal and prismatic and %26lt; c + a %26gt; pyramidal glides) and twinning in compression. It is shown that basal slip is very easy to activate even for small Schmid factors. Numerical simulations reveal that untwinning in tension subsequent to compression must be considered to correctly fit the experimental S-shaped hysteresis curves. TEM observations indicate also intense secondary slips or twins inside the mother twins under cyclic conditions, so that twinning in compression and dislocation glide in tension are affected by cycling. The polycrystalline model allows to predict the macroscopic stress-strain responses, but also slip activities and twin volume fraction evolutions.

• 出版日期2012