Twinning-Detwinning Behavior during Cyclic Deformation of Magnesium Alloy

Abstract

Abstract:In situ neutron diffraction has been used to examine the deformation mechanisms of a precipitation-hardened and extruded .%Al alloy subjected to (i) compression followed by reverse tension (texture T1) and (ii) tension followed by reverse compression (texture T2). Two starting textures are used: (1) as-extruded texture, T1, in which the basal pole of most grains is normal to the extrusion axis and a small portion of grains are oriented with the basal pole parallel to the extrusion axis; (2) a reoriented texture, T2, in which the basal pole of most grains is parallel to the extrusion axis. For texture T1, the onset of extension twinning corresponds well with the macroscopic elastic-plastic transition during the initial compression stage. The non-linear macroscopic stress/strain behavior during unloading after compression is more significant than during unloading after tension. For texture T2, little detwinning occurs after the initial tension stage, but almost all of the twinned volumes are detwinned during loading in reverse compression.

Evolution of Mechanical Twinning during Cyclic Deformation of Mg-Zn-Ca Alloys

“…The most prominent feature of the hysteresis loops observed is their asymmetry, which is often reported for Mg alloys due to the polar nature of mechanical twinning dominating the early deformation stage [53,54]. This asymmetry manifests itself in both the different stress amplitudes in tension and compression and in the different hardening behavior during tensile and compressive parts of the hysteresis loop.…”

Fatigue Performance of Mg-Zn-Zr Alloy Processed by Hot Severe Plastic Deformation

“…Moreover, usually processing via rolling or pressing results in a strong crystallographic texture where the c-axis of the majority of the grains is perpendicular to the longitudinal axis of the product. The strong texture leads to a strong tension-compression asymmetry in deformation [3][4][5][6][7] and is detrimental for fatigue performance.…”

A Review on Capturing Twin Nucleation in Crystal Plasticity for Hexagonal Metals

“…A pseudoelastic behavior was observed upon stress removal during a three-point bending experiment [233], which is associated with untwinning. Experiments have shown that detwinning is not strictly limited to reverse loading but can also occur during unloading [11,192,[234][235][236][237][238][239]. Twinning and detwinning processes have been associated with the pseudoelastic behavior in hcp materials, such as zirconia [148], nitinol [240], and magnesium [238].…”

“…Experiments have shown that detwinning is not strictly limited to reverse loading but can also occur during unloading [11,192,[234][235][236][237][238][239]. Twinning and detwinning processes have been associated with the pseudoelastic behavior in hcp materials, such as zirconia [148], nitinol [240], and magnesium [238]. The final microstructure from the three-point bending experiment shown in Figure 20 shows the role of the second twin variant in accommodating higher strains during the maximum loading.…”