Anisotropic deformation mechanisms of AZ31B Mg alloy under torsional and torsion-axial coupled loadings

doi:10.1016/j.metadv.2026.02.031

Abstract

Abstract:

This study systematically investigates the anisotropic deformation mechanisms of AZ31B magnesium alloy under torsional and torsion-axial coupled loadings, aiming to clarify the mechanisms of shear-dominated multiaxial deformation. Through integrated experiments and numerical simulations, we examine torsional characteristics and torsion-tension/compression coupling effects in AZ31 Mg alloy specimens with varied initial textures. Experiments included free-end torsion and coupled torsion-tension tests, while simulations employed an elastic-viscoplastic self-consistent (EVPSC) model incorporating twinning-detwinning (TDT) mechanisms and a torsion-specific finite element (TFE) methodology. The model accurately reproduces: (1) Highly anisotropic, texture-dependent torsional responses; (2) Complex coupling behaviors under combined loading; (3) Constitutive model-sensitive Swift effects. Mechanistic insights were enhanced by analyzing stress/strain distributions, twin volume fraction (TVF) evolution, deformation mechanism activation, and texture development. These findings bridge the knowledge gap between homogeneous and inhomogeneous deformation in Mg alloys and offer guidance for tailoring twinning activity to enhance formability under complex loading.

Key words: Coupled torsional behavior, Magnesium alloy, Twinning, Texture, Crystal plasticity

Qichang He, Xiaodan Zhang, Yifei Cao, Huamiao Wang, Peidong Wu. Anisotropic deformation mechanisms of AZ31B Mg alloy under torsional and torsion-axial coupled loadings[J]. Metals Advances, 2026, 46: 50-61.

Figures/Tables 19

Fig. 1. (a) Schematic diagrams of cylindrical specimens with three different orientations of ND-, RD-, and 45-samples; (b) initial textures of these samples presented as {0001} pole figures plotted in the θ-r plane.

Table 1. Twisting and axial strain rates used in both experiments and simulations. (Twisting $\dot{\varphi}$ and axial strain rates $\dot{\bar{\varepsilon}}$ (unit: 10−3 s−1)).

Tests	RD-sample		ND-sample		45-sample
Tests	$\dot{\varphi}$	$\dot{\bar{\varepsilon}}$	$\dot{\varphi}$	$\dot{\bar{\varepsilon}}$	$\dot{\varphi}$	$\dot{\bar{\varepsilon}}$
Free-end torsion	1.36	/	80 (Γ<0.038)	/	1.36	/
Fixed-end torsion	1.36	/	1.3 (Γ>0.038)	/	1.36	/
Coupled torsion-tension	2.4	0.47	19 (Γ<0.068)	0.47 (Γ<0.068)	73 (Γ<0.13)	3.9
Coupled torsion-tension	2.4	0.47	2.1 (Γ>0.068)	0.4 (Γ>0.068)	83 (Γ>0.13)	3.9
Coupled torsion-compression	40	−3.9	40	−3.9	40	−3.9

Fig. 2. Schematic representation of TFE approach and the definition of the relevant quantities.

Table 2. Hardening parameters associated with the TFE-EVPSC-TDT model.

Mode	τ₀(MPa)	τ₁(MPa)	h₀(MPa)	h₁(MPa)	h^αβ	A₁	A₂
Basal	10	1	300	0	1
Prismatic	78	55	450	55	1
Pyramidal	100	150	2350	0	1
Extension twin	35	0	0	0	1	0.65	0.75

Fig. 3. (a) Evolution of the average shear stress $\bar{\tau}$ and (b) axial strain $\bar{\varepsilon}$ with respect to applied shear strain Γ during free-end torsion tests for different samples.

Fig. 4. Relative contributions of different deformation mechanisms, along with TVF, during free-end torsion of (a) ND-, (b) RD-, and (c) 45-samples.

Fig. 5. Texture evolution at the outer surface of the samples under free-end torsion (Γ=0.4), presented as {0001} pole figures.

Fig. 6. Stress distributions in three solid rod bars under free-end torsion at shear strain Γ=0.2 and 0.4.

Fig. 7. (a) Evolution of the average shear stress $\bar{\tau}$ and (b) axial stress $\bar{\sigma}$ with respect to applied shear strain Γ during fixed-end torsion tests for different samples.

Fig. 8. Stress distributions in three solid rod bars under fixed-end torsion at shear strain Γ=0.2 and 0.4.

Fig. 9. (a) Evolution of the average shear stress $\bar{\tau}$ with respect to applied shear strain Γ and (b) axial stress $\bar{\sigma}$ with respect to axial strain $\bar{\varepsilon}$ during under coupled torsion-tension for different samples.

Fig. 10. Relative contributions of different deformation mechanisms, along with TVF, under coupled torsion-tension of (a) RD-, (b) ND-, and (c) 45-samples.

Fig. 11. Texture evolution at the outer surface of the samples under coupled torsion-tension (Γ=0.3), presented as {0001} pole figures.

Fig. 12. Stress distributions in three solid rod bars under coupled torsion-tension at shear strains of Γ=0.15 and 0.3.

Fig. 13. (a) Evolution of the average shear stress $\bar{\tau}$ with respect to applied shear strain Γ and (b) axial stress $\bar{\sigma}$ with respect to axial strain $\bar{\varepsilon}$ during under coupled torsion-compression for different samples.

Fig. 14. Relative contributions of different deformation mechanisms, along with TVF, under coupled torsion-compression of (a) RD-, (b) ND-, and (c) 45-samples.

Fig. 15. Texture evolution at the outer surface of the samples under coupled torsion-compression (Γ=0.3), presented as {0001} pole figures.

Fig. 16. Stress distributions in three solid rod bars under coupled torsion-compression at shear strains of Γ=0.15 and 0.3.

Fig. 17. Distribution of the TVF in various rod samples under (a) free-end torsion, (b) fixed-end torsion, (c) coupled torsion-tension, and (d) coupled torsion-compression.

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