The trade-off between strength and ductility has long been a challenge for Mg alloy. To address this issue, bimodal-structured AZ80 Mg alloys with varying heterogeneity levels were fabricated via low-temperature extrusion in this work. The results reveal the microstructure comprising second-phase particle (SP_p, β-Mg₁₇Al₁₂ and Mg₃Mn₂Al₁₈)-reinforced fine grains (FGs) FGs and SP_p-free coarse grains (CGs), with the heterogeneity level decreasing as extrusion temperature increases. As the heterogeneity level decreases, the synergistic deformation capacity initially improves, reaching a maximum at the moderate heterogeneity level of 0.31 GPa and 0.238, and then declines. This exceptional capacity is attributed to the hetero-deformation induced (HDI) stress, which effectively alleviates the strain gradients by activating 〈c + a〉 dislocations and non-basal 〈a〉 dislocations during deformation. An optimal combination of 287 MPa in yield strength, 393 MPa in ultimate tensile strength, and 14.96% in elongation is achieved in the alloy with a moderate heterogeneity level. The excellent strength-ductility synergy originates from the enhanced capacity of dislocations accumulation driven by remarkable capacity of synergistic deformation and the synergistic strengthening mechanisms. This work provides a new insight into the design of bimodal structure to produce high-performance Mg alloys.

(K,Na)NbO₃ (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O₃:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d₃₃ of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d₃₃ of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNNbased single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

In this study, the effects of Mg on the formation of He bubbles and diffusion behavior of He atoms in cubic silicon carbide (3C–SiC) were investigated by irradiation and annealing experiments as well as first-principles calculations. TEM results indicated that two damage bands were formed in He&Mg irradiated SiC. During annealing, Mg could prevent He atoms from diffusing to the surface, resulting in the formation of the He bubbles in the deeper areas far from Mg-implanted regions, which is helpful in avoiding surface blisters. First-principles calculations were then performed to explore the effects of Mg on the He behavior in SiC. The solution energy, binding energy charge density, bond length, and crystal orbital Hamiltonian population of these elements were calculated to identify their states. The results suggested that the binding capacity between He and Mg was weak, and Mg could increase the diffusion energy barrier of He. Ab initio molecular dynamics (AIMD) simulation showed that Mg could make He in a high-energy unstable state, and force He atom to move toward the vacancy away from Mg, which explains the experimental results.