Plastic deformation and fracture behavior of dilute Mg-Al-Ca-Mn alloys with bimodal grain structure

Deformation and fracture behavior of the Mg-1Al-0.2Ca-0.7Mn (wt.%) alloy with a bimodal grain structure were investigated by varying the proportions of recrystallized (RXed) grains. Three samples were prepared with varying proportions of RXed grains at 40 % (F40), 52 % (F50), and 66 % (F65), respectively. The strain distribution among different grains was visualized using the Digital Image Correlation (DIC) technique, and X-ray Computed Tomography (CT) was utilized to observe crack distribution. The results indicate that the sample with 66 % RXed grains demonstrated a favorable strength-ductility balance compared to the other two samples. This can be attributed to its superior capacity for strain transfer and expansion. Among them, the RXed grains promoted strain transmission and inhibited crack propagation, while the unRXed grains assisted in localized strain release and strengthened the alloy. This could enhance understanding of the strength-ductility mechanism in bimodal grain structures.