Improved Tensile Ductility by Severe Plastic Deformation for Nano-Structured Metallic Glass.

Yue Dong,Rainer Wunderlich,Jian-Zhong Jiang,Xiaodong Wang,Qingping Cao,Hans-Jörg Fecht,Johannes Biskupek,Suya Liu

doi:10.3390/ma12101611

Yue Dong, Rainer Wunderlich + Show 6 more

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https://doi.org/10.3390/ma12101611

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Abstract

The effect of severe plastic deformation by high-pressure torsion (HPT) on the structure and plastic tensile properties of two Zr-based bulk metallic glasses, Zr55.7Ni10Al7Cu19Co8.3 and Zr64Ni10Al7Cu19, was investigated. The compositions were chosen because, in TEM investigation, Zr55.7Ni10Al7Cu19Co8.3 exhibited nanoscale inhomogeneity, while Zr64Ni10Al7Cu19 appeared homogeneous on that length scale. The nanoscale inhomogeneity was expected to result in an increased plastic strain limit, as compared to the homogeneous material, which may be further increased by severe mechanical work. The as-cast materials exhibited 0.1% tensile plasticity for Zr64Ni10Al7Cu19 and Zr55.7Ni10Al7Cu19Co8.3. Following two rotations of HPT treatment, the tensile plastic strain was increased to 0.5% and 0.9%, respectively. Further testing was performed by X-ray diffraction and by differential scanning calorimetry. Following two rotations of HPT treatment, the initially fully amorphous Zr55.7Ni10Al7Cu19Co8.3 exhibited significantly increased free volume and a small volume fraction of nanocrystallites. A further increase in HPT rotation number did not result in an increase in plastic ductility of both alloys. Possible reasons for the different mechanical behavior of nanoscale heterogeneous Zr55.7Ni10Al7Cu19Co8.3 and homogeneous Zr64Ni10Al7Cu19 are presented.

Highlights

Metallic glasses (MGs), discovered in 1960 [1], are metallic bonded amorphous solids with no long-range translation/orientation order, formed by quenching from melt
It was found that the homogeneous structure of Zr-0Co MG remained fully amorphous during
Nanocrystalline particles appeared in the Zr-8Co MG because of the lower thermal stability

Summary

Introduction

Metallic glasses (MGs), discovered in 1960 [1], are metallic bonded amorphous solids with no long-range translation/orientation order, formed by quenching from melt. Short-range topological and chemical orders on a length scale of 0.5–1 nm are often detected in MGs. More than two decades ago, multicomponent bulk metallic glass-forming alloys were synthesized [2,3,4,5,6,7,8,9]. Lacking a crystalline structure with dislocations, the mechanical deformation of MGs in tension is concentrated in a single or a few shear bands (SBs). Even though quite large ductility can be observed under constrained loading, such as in compression, tensile strain leads to catastrophic failure without plasticity, which restricts the potential application of MGs as structural materials [17,18]

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