Source：Southeast University College of Materials Science
Recently, the team led by Professor Shen Baolong from the School of Materials Science and Engineering of Southeast University and the Key Laboratory of Advanced Metal Materials for High Technology of Jiangsu Province has continuously made significant breakthroughs in the field of materials science frontiers. Two innovative research results were successively published online in the international top journal "Nature Communications", achieving key technological breakthroughs in the plastic optimization of amorphous alloys and the improvement of high-temperature performance of refractory binary-entropy alloys. These achievements provide important support for related fields of materials.
Professor Shen Baolong's team published an important progress in the research on the mechanical properties of amorphous alloys in "Nature Communications". This research result, titled "Transformation-mediated and relaxation-assisted macroscopic tensile plasticity with strain-hardening in metallic glass", was the first to achieve 10% macroscopic tensile plasticity and strain-hardening effect in iron-based amorphous soft magnetic alloys, revealing a new mechanism of strong toughness through the synergy of structural transformation and relaxation. It provides new ideas for solving the problems of the lack of stable plastic flow ability and relaxation-induced brittleness in amorphous alloys.
Amorphous alloys have excellent properties such as high strength, large elastic limit and corrosion resistance, and have broad application prospects in aerospace, biomedicine, energy equipment and other fields. Among them, iron-based amorphous alloys also have excellent soft magnetic properties. Developing new amorphous alloys with both high strength and excellent soft magnetic properties is of great strategic significance for improving the independent supply and industrial competitiveness of key materials in fields such as new energy, information communication and low-altitude economy in China.
The team proposed a new structural control strategy based on the regulation of the rate of cold and hot cycling treatment, forming multi-scale heterogeneous structures through stress-induced formation. During the tensile process, multiple mechanisms work together to achieve significant improvement in plasticity: the activation energy of β relaxation is significantly reduced, promoting the coordinated activation of a large number of shear transformation zones, effectively suppressing the localization of shear bands; irreversible structural relaxation forms a nano-network structure adjacent to rich iron mesoscopic ordered clusters and rich metal clusters through free volume annihilation, thereby inhibiting the rapid expansion of shear bands; the multi-scale heterogeneous structure induces the deflection and bifurcation of shear bands; shear stress drives the mesoscopic ordered structure to transform into α-Fe nanocrystals, and the lattice distortion and dislocation formation in the nanocrystals further contribute to strain hardening. In addition, this strategy is applicable in various amorphous alloy systems such as Cu-based and Er-based. This research not only deepens the understanding of the plastic deformation mechanism of amorphous alloys, but also, after more than 60 years since the discovery of amorphous alloys, for the first time achieves "rigidity and toughness in harmony" excellent tensile performance at the macroscopic scale: maintaining a high tensile strength of 1680 MPa while demonstrating 10% macroscopic tensile plasticity and significant strain hardening, breaking through its long-standing brittleness bottleneck, and providing a solution for promoting the wider application of amorphous alloys as structural and functional materials.
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