Enhanced mechanical properties and electromagnetic interference shielding effectiveness in Mg‐6Zn‐1Y‐1La‐0.5Zr alloy sheet by hot deformation

Striking a balance between the mechanical properties and electromagnetic interference shielding effectiveness (EMI SE) of Mg alloys stands as a critical concern within the realm of electronics and communications. This study endeavors to optimize the mechanical properties and EMI SE of Mg alloy sheets through a combination of extrusion and rolling (E-R). OM, SEM, XRD, EBSD, and TEM obtained the microstructures of Mg‐6Zn‐1Y‐1La‐0.5Zr alloys under extrusion and different rolling strain treatments, and the effects of the microstructures on the mechanical properties and EMI SE were revealed. The microstructure of the as-extruded Mg‐6Zn‐1Y‐1La‐0.5Zr (abbreviated as ZKL611K) alloy exhibited a distinct bimodal microstructure, with refined dynamically recrystallized (DRXed) grains surrounding coarse unDRXed regions. Subsequent rolling treatments induced a decrease in the aspect ratio of the unDRXed regions, a rapid reduction of DRXed grains, and the accumulation of dislocations within the as-rolled alloy. Statistical analysis of mechanical properties and EMI SE revealed that an optimal balance in the sheets subjected to “extrusion + 37 % rolling reduction”, yield strength (YS) of 319 MPa, ultimate tensile strength (UTS) of 375 MPa, and elongation of 12.3 %. Furthermore, the EMI SE ranged from 81 dB to 114 dB within the frequency range of 30–1500 MHz. However, further increments in rolling reduction adversely affected mechanical properties while improving EMI SE. The observed enhancement in mechanical properties can be primarily attributed to the synergistic effects of grain size, second phase, dislocations, low-angle grain boundaries (LAGBs), and texture. Meanwhile, the improved EMI SE can be mainly attributed to the diffuse distribution of the second phase at multiple scales and the modulation of the texture through E-R treatments.