Work-Hardening Induced Tensile Ductility of Bulk Metallic Glasses via High-Pressure Torsion

Abstract

The mechanical properties of engineering materials are key for ensuring safety and reliability. However, the plastic deformation of BMGs is confined to narrow regions in shear bands, which usually result in limited ductilities and catastrophic failures at low homologous temperatures. The quasi-brittle failure and lack of tensile ductility undercut the potential applications of BMGs. In this report, we present clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process. Enhanced tensile ductility and work-hardening behavior after the HPT process were investigated, focusing on the microstructure, particularly the changed free volume, which affects deformation mechanisms (i.e., initiation, propagation, and obstruction of shear bands). Our results provide insights into the basic functions of hydrostatic pressure and shear strain in the microstructure and mechanical properties of HPT-processed BMGs.

Ductile bulk metallic glass by controlling structural heterogeneities

“…On the other hand, only a few effective methods for improving the tensile ductility of BMGs have been developed so far. These methods, which also generate heterogeneous microstructures, include cold rolling 19,20 , high-pressure torsion 21 and surface mechanical attrition 22 . Although the effectiveness of heterogeneous microstructures for enhancing the tensile ductility of BMGs has been established 19–22 , the limits of this approach have not been fully evaluated yet.…”

Influence of HPT Deformation on the Structure and Properties of Amorphous Alloys

“…The deformation behavior of the initial, compressed, and HPT specimens was investigated. The yield strengths of the initial and compressed BMG were similar (Figure 11a) [85]. The tensile deformation behaviors of the HPT specimens were different as compared with that of initial BMG.…”

“…Herewith, it can lead to the formation of a high density of shear bands, where the spacing between the bands is about 50-100 nm [50]. In other works [24,41,[52][53][54][55][56][57]85], shear bands were not observed in the amorphous structure after HPT processing.…”

“…The changes in the fracture surfaces can be interpreted as a successive increase of the material's local ductility due to HPT, which is connected with changes in the structure after HPT. Enhanced tensile ductility of the Zr65Al7.5Ni10Cu12.5Pd5 BMG after HPT was reported in [85]. The BMG was subjected to a compression stage and HPT processing.…”

Metallic Glass Matrix Composites

“…To date, there are several ways that have been developed to improve the room-temperature plasticity of BMGs, including intruding a secondary phase to develop a composite microstructure, surface coating, composition adjustment to induce intrinsic heterogeneity, severe plastic deformation such as shot peening and high pressure torsion [24][25][26][27]. Although introducing a secondary phase to make a composite structure seems to be most primal methods, it is reported that composite structure is one of the most efficient method and very easy to realize.…”