Substantially enhanced plasticity of bulk metallic glasses by densifying local atomic packing

Yuan Wu,Zhaoping Lu,Dierk Raabe,Paraskevas Kontis,Jinyue Wang,Huihui Zhu,Suihe Jiang,Hui Wang,Baptiste Gault,Di Cao,Yilin Yao,Fengshou Li,Guosheng Zhang,Xiongjun Liu,Xianzhen Wang,Leqing Liu,Huiyang Fan

doi:10.1038/s41467-021-26858-9

Abstract

Introducing regions of looser atomic packing in bulk metallic glasses (BMGs) was reported to facilitate plastic deformation, rendering BMGs more ductile at room temperature. Here, we present a different alloy design approach, namely, doping the nonmetallic elements to form densely packed motifs. The enhanced structural fluctuations in Ti-, Zr- and Cu-based BMG systems leads to improved strength and renders these solutes’ atomic neighborhoods more prone to plastic deformation at an increased critical stress. As a result, we simultaneously increased the compressive plasticity (from ∼8% to unfractured), strength (from ∼1725 to 1925 MPa) and toughness (from 87 ± 10 to 165 ± 15 MPa√m), as exemplarily demonstrated for the Zr20Cu20Hf20Ti20Ni20 BMG. Our study advances the understanding of the atomic-scale origin of structure-property relationships in amorphous solids and provides a new strategy for ductilizing BMG without sacrificing strength.

Highlights

Introducing regions of looser atomic packing in bulk metallic glasses (BMGs) was reported to facilitate plastic deformation, rendering BMGs more ductile at room temperature
Plastic deformation in BMGs well below their glass transition temperature mainly arises from local diffusive jumps[8], or some local events of cooperative shearing of atomic clusters termed shear transformation zones (STZs)[9,10], whereby a group of atoms cooperatively overcomes the saddle point of the energy barrier for local atomic rearrangement[11,12]
We studied the equiatomic Zr20Cu20Hf20Ti20Ni20 BMG doped with 0.1, 0.2, 0.3, and 0.5 at.% of one of the nonmetallic elements (NMEs) oxygen, nitrogen, carbon, and boron

Summary

Introduction

Introducing regions of looser atomic packing in bulk metallic glasses (BMGs) was reported to facilitate plastic deformation, rendering BMGs more ductile at room temperature. The site where local shear transformation starts is still hard to predict, it is well accepted that introducing more loosely packed regions is effective in facilitating local plastic events in BMGs13,14 These regions are associated with a high local potential energy and prone to inelastic deformation upon loading, exhibiting a liquid-like behavior[13]. We identify suited doping regimes (ranging from 0.1% to 0.3%) where we observed an appreciable rise in strength and ductility This can be ascribed to the increase in the volume fraction of local dense packing regions (LDPRs) forming around these nonmetallic solutes, whilst avoiding the formation of brittle secondary phases. In terms of an adequate negative heat of mixing associated with these dopants, our approach is in principle universal and could be deployed to improve the properties of a wide range of MGs

Methods

Results

Conclusion