Crystallographic slips and twinning activity in AZ31 magnesium alloy during different modes of deformation on the basis of diffraction experiment and modelling

This study investigates the plastic deformation behaviour of the AZ31 magnesium alloy under various uniaxial loading conditions using in-situ neutron diffraction, the crystallite group method (CGM), and crystal plasticity modelling. A key novelty of this work is the direct, model independent determination of resolved shear stress (RSS) values for individual slip and twinning systems, as well as their critical values (CRSS), derived from lattice strains in grains with preferred orientations. The experiment was extended beyond the conventional loading paths along the normal direction (ND) and rolling direction (RD) to include compression at angles of 30° and 60° from the ND (referred to as NDC30 and NDC60 tests), which had not been investigated in previous studies. Notably, the NDC30 test, combined with diffraction measurements, was specifically designed to activate basal slip in the majority of grains while minimizing twinning, enabling clear identification of this slip system and accurate determination of its CRSS.

For the first time, hardening parameters were determined by comparing the model predicted values of RSS with those obtained from diffraction measurements for each active system. These data, together with the results of macroscopic tests, were used to calibrate an elastic-plastic self-consistent (EPSC) model, which accurately reproduced stress partitioning under applied load, texture evolution, and twin activity. The integrated methodology enhances the reliability of CRSS input and improves the modelling of anisotropic plasticity in magnesium alloys by tuning intergranular interactions based on a modified Eshelby inclusion approach.