Jan Čapek

In-situ neutron diffraction and acoustic emission investigation of twinning activity in magnesium

The neutron diffraction and acoustic emission (AE) techniques have been used for in-situ investigation of deformation twinning activity in cast polycrystalline magnesium at room temperature. The combination of these two techniques results in obtaining complementary information about the twinning mechanism during the straining. It is shown that loading mode significantly influences the twin nucleation and the twin size. In tension, the twin nucleation is observed during the entire test, while in compression only at the beginning of the plastic deformation. Nevertheless, the overall twinned volume does not differ. The optical micrographs support the above mentioned conclusions.

Investigation of Twinning Activity in Magnesium Using Advanced In Situ Methods

The high-resolution neutron diffraction and acoustic emission (AE) techniques have been used for in-situ investigation of deformation twinning and microstructure evolution in cast polycrystalline magnesium. The combination of these two techniques results in obtaining complementary information about the twinning mechanism and evolution of the dislocation structure during the straining. The dependence of the mechanisms of the plastic deformation on loading mode is discussed in detail. The microscopy investigations revealed a difference in twin number and size after tension and compression, respectively.

In Situ Neutron Diffraction and Acoustic Emission During the Biaxial Loading of AZ31 Alloy

The evolution of twinning in randomly textured magnesium alloy and rolled AZ31 alloy during biaxial mechanical tests has been monitored using concurrent application of acoustic emission and neutron diffraction methods. The influence of the loading path on twinning is discussed in detail. It is shown that the twinning is strongly sensitive to the load path.

Neutron Diffraction and Acoustic Emission Measurement During Loading and Unloading of Magnesium Aluminium Binary Alloys

The neutron diffraction and acoustic emission were measured during compression loading-unloading tests in randomly textured cast magnesium and magnesium 2 and 9 wt% aluminium binary alloys. The anelastic behavior and the change of twinned volume related to the detwinning phenomena can be observed during the unloading. The decrease of twinned volume fraction during unloading is most pronounced for Mg 9 wt%Al.

Influence of the Loading Path on the Deformation Mechanisms of Magnesium Alloys

The evolution of deformation mechanisms in randomly textured magnesium alloy during uniaxial and biaxial mechanical tests has been monitored using concurrent application of acoustic emission and neutron diffraction methods. The influence of the loading path on both twinning and dislocation slip is discussed in detail. It is shown that both the twinning and non-basal slip are sensitive to the loading direction.

The Use of Acoustic Emission and Neutron Diffraction to Reveal the Active Deformation Mechanisms in Polycrystalline Magnesium and Comparison to Theoretical Modeling

A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly textured cast magnesium is presented. An elasto-plastic self-consistent model (EPSC) is used to model the evolution of the dislocation structure and twinning. The results are quantitatively compared with experimental data obtained by in-situ neutron diffraction (ND) and acoustic emission (AE) methods. Both EPSC calculations and ND line profile analysis show an increased activity of prismatic slip with increasing strain and a loading mode dependence of the activity of the second-order pyramidal slip. The AE measurements and the modeling indicate different amount of nucleated twin variants and twinned volume in tension and compression, respectively.