On the origin of softening in the plastic deformation of metallic glasses

doi:10.1016/j.ijplas.2018.12.004

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	On the origin of softening in the plastic deformation of metallic glasses
	Zhang M1,2 ; Chen Y(陈艳)2,3 ; Li W 1
通讯作者	Zhang, M.(m.zhangiwrm@jnu.edu.cn)
发表期刊	INTERNATIONAL JOURNAL OF PLASTICITY
	2019-05-01
卷号	116 页码:24-38
ISSN	0749-6419
摘要	In the plastic deformation of amorphous materials, dilatation occurs universally with softening. However, the critical question that whether softening is caused by dilatation or not remains an ansatz and requires experimental examination. In this work, by examining the deformation behaviors of 3 metallic glasses (MGs) with distinct Johari-Goldstein (JG) relaxation characteristics before and after crystallization with nanoindentation, it is found that the origin of softening is probably not dilatation but the collective mode in the activation dynamics of shear transformation zones (STZs). Since the deformation in the creep stage of nanoindentation of the MGs originates from the "delayed plasticity" from the loading stage and depends on the softened deforming state of the MGs, the creep depth vs. time curves in the creep stage of nanoindentation of the MGs are examined and display similar loading rate dependent softening phenomena for both the glassy and crystallized MGs. The stretched exponent and relaxation time characterizing the deformation dynamics in the creep stage of nanoindentation are derived by fitting the creep depth vs. time curves with the Kohlrausch-Williams-Watts (KWW) equation. The stretched exponents indicate similar collective modes in the activation dynamics of the elementary deformation units (STZs in glassy MGs and dislocations in crystallized MGs). The relaxation times manifest similar softening effects in the deformation accommodation processes of both the glassy and crystallized MGs, except for a glassy La MG of which the relaxation time is extraordinary for its pronounced JG relaxation. The extraordinary relaxation time of the glassy La MG precludes the possibility of shear dilatation being the main cause for the softening of the glassy La MGs indicated by the loading rate dependent creep depth vs. time curves. The stretched exponent and the relaxation time indicate the homological softening dynamics in the plastic deformation of the glassy and crystallized MGs. For the distinct elementary deformation units, i.e., STZs in glassy MGs and dislocations in crystallized MGs, noting the absence of dilatation in dislocation movements, the softening phenomena in the plastic deformation of both the glassy and crystallized MGs is suggested to originate from the collective mode in the activation dynamics of the elementary deformation units, rather than from local properties of elementary deformation units, such as dilatation in STZs.
关键词	Metallic glass Softening Nanoindentation Structural relaxation
DOI	10.1016/j.ijplas.2018.12.004
收录类别	SCI ; EI
语种	英语
WOS记录号	WOS:000463303400002
关键词[WOS]	NANOINDENTATION CREEP-BEHAVIOR ; SERRATED FLOW ; INSTRUMENTED INDENTATION ; RATE DEPENDENCE ; RELAXATION ; TEMPERATURE ; NANOCRYSTALLINE ; INSTABILITY ; ROOM ; COMPRESSION
WOS研究方向	Engineering ; Materials Science ; Mechanics
WOS类目	Engineering, Mechanical ; Materials Science, Multidisciplinary ; Mechanics
资助项目	National Nature and Science Foundation of China[51701082] ; Fundamental Research Funds for the Central Universities ; Guangdong Province Science and Technology Plan[2017B090903005] ; Opening Fund of State Key Laboratory of Non-linear Mechanics[LNM201812]
项目资助者	National Nature and Science Foundation of China ; Fundamental Research Funds for the Central Universities ; Guangdong Province Science and Technology Plan ; Opening Fund of State Key Laboratory of Non-linear Mechanics
论文分区	一类
力学所作者排名	2
RpAuthor	Zhang, M.
引用统计	被引频次：21[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://dspace.imech.ac.cn/handle/311007/78714
专题	非线性力学国家重点实验室
作者单位	1.Jinan Univ, Inst Adv Wear & Corros Resistant & Funct Mat, Guangzhou 510632, Guangdong, Peoples R China; 2.Chinese Acad Sci, Inst Mech, State Key Lab Nonlinear Mech, Beijing 100190, Peoples R China; 3.Univ Chinese Acad Sci, Sch Engn Sci, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Zhang M,Chen Y,Li W. On the origin of softening in the plastic deformation of metallic glasses[J]. INTERNATIONAL JOURNAL OF PLASTICITY,2019,116:24-38.
APA	Zhang M,陈艳,&Li W.(2019).On the origin of softening in the plastic deformation of metallic glasses.INTERNATIONAL JOURNAL OF PLASTICITY,116,24-38.
MLA	Zhang M,et al."On the origin of softening in the plastic deformation of metallic glasses".INTERNATIONAL JOURNAL OF PLASTICITY 116(2019):24-38.

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