Incipient deformation twinning in dynamically sheared bcc tantalum

被引：43

作者：

Chen, C. Q. ^{[1
,2
]}

Florando, J. N. ^{[3
]}

Kumar, M. ^{[3
]}

Ramesh, K. T. ^{[1
,2
]}

Hemker, K. J. ^{[1
,2
]}

机构：

[1] Johns Hopkins Univ, Dept Mech Engn, Baltimore, MD 21218 USA

[2] Johns Hopkins Univ, Hopkins Extreme Mat Inst, Baltimore, MD 21218 USA

[3] Lawrence Livermore Natl Lab, Mat Engn Div, Livermore, CA 94550 USA

来源：

ACTA MATERIALIA | 2014年 / 69卷

关键词：

Incipient deformation twinning; bcc Tantalum; Dynamic shear; Transmission electron microscopy; Twinning mechanism; EMISSARY DISLOCATIONS; SCREW DISLOCATIONS; TWINS; NUCLEATION; GROWTH; SLIP; MECHANISM; METALS; MO-35;

D O I：

10.1016/j.actamat.2014.01.046

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

Mechanical twinning has been introduced into a body-centered cubic metal, tantalum, through shear-dominant dynamic loading at a high shear strain rate (up to 3 x 10(4)/s) at 77 K. Direct measurement of shear stress combined with transmission electron microscopy (TEM) confirmed the occurrence of deformation twinning at applied global shear stresses of 520 MPa and above. The TEM characterization was focused on nanometer-sized individual twins that are interspersed and aligned in association with slip bands. These small twins belong to the {1 1 2} (1 1 1) twinning system but show unusual morphologies and growth characteristics, and are believed to be incipient twins at the early stages of their development. TEM analysis revealed a multifaceted growth characteristic of the incipient twins following at least two {1 1 2} planes in the (1 1 1) zone. While the formation of a macroscopic twin is a result of growth and coalescence of an array of small twins, the early stage growth of an incipient twin is rationalized through a slip-assisted double-cross-slip growth mechanism. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

引用

页码：114 / 125

页数：12

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