Superior Tensile Ductility in Bulk Metallic Glass with Gradient Amorphous Structure

Abstract

Over centuries, structural glasses have been deemed as a strong yet inherently ‘brittle’ material due to their lack of tensile ductility. However, here we report bulk metallic glasses exhibiting both a high strength of ~2 GPa and an unprecedented tensile elongation of 2–4% at room temperature. Our experiments have demonstrated that intense structural evolution can be triggered in theses glasses by the carefully controlled surface mechanical attrition treatment, leading to the formation of gradient amorphous microstructures across the sample thickness. As a result, the engineered amorphous microstructures effectively promote multiple shear banding while delay cavitation in the bulk metallic glass, thus resulting in superior tensile ductility. The outcome of our research uncovers an unusual work-hardening mechanism in monolithic bulk metallic glasses and demonstrates a promising yet low-cost strategy suitable for producing large-sized, ultra-strong and stretchable structural glasses.

Macroscopic tensile plasticity of Zr-based bulk metallic glass with surface screw thread shaped structure

“…A question is then raised: How could we extend the local plastic deformation into the macroscopic tensile plasticity rather than the brittle fracture governed by a thin main SB? Recent work showed that the macroscopic tensile plasticity could be obtained by introducing the artificial micro-structural defects, such as the notches [15,16], the surface indentations [17], the designing hole array [18] and laser shock peening treatment [19]. These results indicate that the formation of multiple SBs and the stable propagation of main SBs are the two key factors for improving the tensile plasticity of BMGs.…”

Tensile behavior of Cu-coated Pd40Cu30Ni10P20 metallic glassy wire

“…However, in tension, the tensile stress enhances softening and instability, a dominant shear band slips without obstacle, and bulk and micro-sized MGs fracture elastically 3 . Various approaches have been introduced to retard the dominant shear band to improve tensile ductility of bulk and micro-sized MGs, such as designing MG matrix composites 4,5 , sharp-and-deep notches 6 , laminating MG with ductile crystalline metals 7,8 , surface mechanical treatment 9–11 , laser surface texturing treatment 12 , and MG-based chiral nanolattice 13 . In addition, size reduction approach changes room temperature plastic deformation mechanism of MG from shear banding into homogeneous plastic flow 14–18 .…”

Enhanced tensile plasticity of Zr based bulk metallic glasses by a stress induced large scale flow

“…However, in the constrained stress field such as compression and bending, considerable plastic in BMGs can be achieved by multiple shear bands [10e14]. Based on this mechanism, substantial efforts have been made to enhance the tensile ductility of MGs, such as introducing heterostructures [15], notching [16,17], surface treatment [18,19] and cold working [20]. Nevertheless, the flow is still constrained in shear band and the ductility is also carried by multiple shear bands.…”