Designing Al-Based complex confused metallic glasses via chemically complex alloying and crystallization confusion

• Designing Al-based complex confused metallic glasses with high GFA and increased fragility. • Synergy effects induced by chemically complex alloying and enhanced crystallization confusion. • Overcoming the inherent thresholds limiting the ΔT x and GFA in Al-Ni-RE MGs with single RE. • Higher proportion of the soft mode of first-pop-ins mediated by complex RE-Al interactions. • Push the boundaries for the optimization of multi-major characteristics in metallic glasses. Herein, we report a new alloy design strategy for Al 84 Ni 10 RE 6 metallic glasses by incorporating multiple equiatomic RE elements (RE = La, Ce, Nd, Gd, Y, Er) while manipulating their electronegativity differences close to the critical value at the transition boundary between eutectic and primary crystallization. The resulting Al 84 Ni 10 (NdGdY or NdGdYEr) 6 MGs close to Δ ψ c r i t , referred to as complex confused metallic glasses (CCMGs), exhibit synergistic effects of complex RE-Al bonding and crystallization confusion. These effects overcome inherent limitations in the supercooled liquid region (Δ T x ) and glass forming ability (GFA) observed in Al-Ni-RE MGs with a single RE. Flash DSC study confirmed that the Al 84 Ni 10 (NdGdY or NdGdYEr) 6 CCMGs show a 50 % reduction of critical cooling rate for glass formation than those of Al 84 Ni 10 (La or Er) 6 MGs while having ∼ 15 % larger fragility index. The statistical nanoindentation test exhibited the distinct bimodal distribution of shear band nucleation in the Al 84 Ni 10 (NdGdY or NdGdYEr) 6 CCMGs, with a higher proportion of the soft mode attributed to loosely packed regions-indicative of more fragile behavior mediated by complex RE-Al interaction. Consequently, our study provides a new strategy to optimize multiple key properties of Al-based CCMGs, enabling simultaneous enhancement of GFA, fragility, and intrinsic plasticity.