Correlation of microstructure and tensile properties in in-situ high-entropy bulk metallic glass composites

To investigate the ‘structure-property’ correlation in the high-entropy bulk metallic glass composites (HE-BMGCs), a series of in-situ dendrites-reinforced Zr ₂₈Ti ₁₉Hf ₁₉Nb _9.5Co _5.5Be ₁₉ HE-BMGCs containing different microstructures are fabricated by varying the cooling rate ( R). The underlying correlation between microstructure characteristics of dendrites and tensile properties of HE-BMGCs are elucidated by the postmortem microstructure observation and fracture analysis. The critical investigation shows the volume fraction ( V_d), size ( δ) and arm diameter ( d) of dendrite increase with decreasing R, whereas the interdendritic spacing ( λ) decreases correspondingly. The larger d is more beneficial to enhance the back-stress-induced hardening effect of HE-BMGCs, while the strengths of all the HE-BMGCs are negative linear correlation with their V_d (56∼70%). Besides, the finer δ matches the size of ‘plastic zone’ associated with larger λ, which results in higher tensile ductility (∼6.4%). Therefore, the combination of finer δ and appropriate V_d at higher R is favorable for HE-BMGCs to obtain better ductility and higher strength. Our findings provide an important implication for the microstructural optimization of HE-BMGCs with desirable mechanical properties.