Phase transition of iron-based single crystals under ramp compressions   with extreme strain rates

doi:10.1016/j.ijplas.2017.04.016

CORC > 北京大学 > 工学院

	Phase transition of iron-based single crystals under ramp compressions with extreme strain rates
	Wang, Kun ; Chen, Jun ; Zhu, Wenjun ; Hu, Wangyu ; Xiang, Meizhen
刊名	INTERNATIONAL JOURNAL OF PLASTICITY
	2017
关键词	Phase transition Strain rate Strain gradient Lattice instability Molecular dynamics Dynamic loading Metal HIGH-PRESSURE HOMOGENEOUS CRYSTALS INDUCED PLASTICITY LATTICE-DYNAMICS INSTABILITIES MODEL DEFORMATION TRANSFORMATIONS STEELS
DOI	10.1016/j.ijplas.2017.04.016
英文摘要	Recent widespread interests on strain rate effects of phase transition under dynamic loadings bring out present studies. alpha -> epsilon phase transition of iron, as a prototype of martensite phase transition under dynamic loadings, exhibits huge diverges in its transition pressure (TP) among experiments with different pressure medium and loading rates, even in the same initial samples. Great achievements are made in understanding strain or stress dependence of the TP under dynamic loadings. However, present understandings on the strain rate dependence of the TP are far from clear, even a virgin for extreme high strain rates. In this work, large scale nonequilibrium molecular dynamics simulations are conducted to study the effects of strain rates on the phase transition of iron-based single crystals. Our results show that the phase transition is preceded by lattice instabilities under ramp compressions, but present theory, represented by modified Born criteria, cannot correctly predict observed onsets of the instability. Through considering both strain and strain gradient disturbances, new instability criteria are proposed, which could be generally applied for studying instabilities under either static or dynamic loadings. For the ramp with a strain rate smaller than about 10(10) s(-1), the observed onset of instabilities is indeed equal to the one predicted by the new instability criteria under small gradient disturbances. The observed onsets deviates from the predicted one at lager strain rates because of finite strain gradient effect - nonzero higher order stresses and work conjugates of the strain gradient. Interestingly, the strain rate ((epsilon) over dot) dependence of the TP also exhibits an obvious change at the same strain rate, i.e., 10(10) s(-1). When (epsilon) over dot <= 10(10) s(-1) a certain power law is obeyed, but it is not applicable at larger strain rates. This strain rate effect on the TP is well interpreted with nucleation time and the finite strain gradient effect. According to these basic understandings, the roles of strain rates on nucleation and growth of the phase transition are studied. Besides, initial shock formation time at extreme strain rates is analyzed, which also exhibits a deviation from a scaling law. (C) 2017 Elsevier Ltd. All rights reserved.; National Natural Science Foundation of China [NSFC-NSAF 11076012, NSFC 11102194, 11402243]; National Key Laboratory Project of Shock Wave and Detonation Physics [077120]; Science and Technology Foundation of National Key Laboratory of Shock Wave and Detonation Physics [9140C670201110C6704, 9140C6702011103]; Chinese National Fusion Project for ITER [2013GB114001]; SCI(E); ARTICLE; 56-80; 96
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/471262]
专题	工学院
推荐引用方式 GB/T 7714	Wang, Kun,Chen, Jun,Zhu, Wenjun,et al. Phase transition of iron-based single crystals under ramp compressions with extreme strain rates[J]. INTERNATIONAL JOURNAL OF PLASTICITY,2017.
APA	Wang, Kun,Chen, Jun,Zhu, Wenjun,Hu, Wangyu,&Xiang, Meizhen.(2017).Phase transition of iron-based single crystals under ramp compressions with extreme strain rates.INTERNATIONAL JOURNAL OF PLASTICITY.
MLA	Wang, Kun,et al."Phase transition of iron-based single crystals under ramp compressions with extreme strain rates".INTERNATIONAL JOURNAL OF PLASTICITY (2017).