Probe Embryonic Damage Evolution in Bulk Metallic Glasses under Plate-impact Loading

Zhong Ling,Lanhong Dai,Xin Huang,E Buzaud,E Cadoni,A Cosculluela,H Couque

doi:10.1051/epjconf/201818303013

Abstract

Microdamage in very short stress durations of spallation process in Zr-based bulk metallic glass (Zr-BMG) samples were captured by a specially designed plate impact technique. With stress durations vary, microdamage “frozen” in Zr-BMG samples exhibited different damage levels. Based on the morphology and stress environment of the microdamage, a compound microdamage evolution mode is applied to characterize the spallation evolution in Zr-BMGs. Especially the spallation in BMGs originates from cavitation instabilities in the weak regions with higher free volume content, which results in formation of ductile damage zones. The activation of shear transformation zones (STZs) or tension transformation zones (TTZs) between these ductile damage zones finally leads to detached spallation.

Highlights

Spallation is a dynamic failure phenomenon of solids under impulsive loadings, which is generated by interaction of release waves reflected from free surfaces [1]
As the zipshaped cracks or vain patterns are observed on crosssections or spall surfaces of recovered bulk metallic glasses (BMGs) samples in plate-impact experiments [9, 10], it is believed that the spallation results from formation and development of shear bands
The clear pictures of early-stage spallation damages were observed on the recovered Zr-based bulk metallic glass (Zr-BMG) samples after the plate-impact tests

Summary

Introduction

Spallation is a dynamic failure phenomenon of solids under impulsive loadings, which is generated by interaction of release waves reflected from free surfaces [1]. As the zipshaped cracks or vain patterns are observed on crosssections or spall surfaces of recovered BMG samples in plate-impact experiments [9, 10], it is believed that the spallation results from formation and development of shear bands. Another view contends that the spallation is a mean tensile stress dominated cavitation process. The clear pictures of early-stage spallation damages were observed on the recovered Zr-BMG samples after the plate-impact tests. A damage evolution mode is proposed to understand the spallation mechanism in BMGs

Materials and experiments

Microscopic observations

Microdamage evolution mode

Stress and strain environment

Microstructure heterogeneity

Compound damage evolution mode