Abstract
Friction stir welding (FSW) is a promising solid-state joining process for magnesium al-loys that avoids defects characteristic of fusion welding. In the present study, a three-dimensional, fully coupled thermomechanical model of FSW of two 3.0-mm-thick MA2-1 (AZ31B) alloy plates was developed using the Coupled Eulerian–Lagrangian (CEL) approach in Abaqus/Explicit. The constitutive behavior of the material was de-scribed using the Johnson–Cook model (A = 172 MPa, n = 0.456, m = 0.90), while contact interaction was represented by a modified Coulomb–Tresca friction law (μ = 0.40, δ = 0.60). A parametric study of 11 configurations was performed by varying the shoulder diameter R_sh (6–12 mm), pin diameter R_pin (2–4 mm), rotational speed ω (600–1200 rpm), and traverse speed v (60–180 mm/min). A functional specialization of the parame-ters was established: R_sh dominates the thermal regime (exponent +0.58 for T_peak) and the stress state (−1.67 for σ_mean); R_pin controls the width of the stirring zone (W_mix, exponent +0.88); and rotational speed ω is the key factor governing AS/RS deformation asymmetry (K_asm(PEEQ) = 1.10–1.40). Power-law regression equations were obtained for T_peak, σ_mean, PEEQ_max, and W_mix, with R² ≥ 0.95. Spatial correlation analysis confirmed the independence of the thermal and deformation zones, with r(T, PEEQ) = 0.07. Principal component analysis (PCA) identified two dominant mechanisms: a 'com-mon interaction zone' (PC1, 44.7%) and an HAZ–TMAZ antiphase (PC2, 23.7%).