In Situ Studies on the Irradiation-Induced Twin Boundary-Defect Interactions in Cu
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In Situ Studies on the Irradiation-Induced Twin Boundary-Defect Interactions in Cu C. FAN, JIN LI, ZHE FAN, H. WANG, and X. ZHANG Polycrystalline Cu films with nanoscale annealing twins are subjected to in situ Kr++ ion irradiation at room temperature inside a transmission electron microscope up to a dose of 1 displacement-per-atom. Radiation induces prominent migration of incoherent twin boundaries. Depending on twin thickness, three types of twin boundary evolutions are observed, including rapid detwinning, gradual detwinning, and self-healing. The mechanism of twin thickness-dependent evolution of microstructures is discussed. This study provides further evidence on twin boundary-defect interactions and may assist the design of radiation-tolerant twinned metallic materials. DOI: 10.1007/s11661-017-4293-5 The Minerals, Metals & Materials Society and ASM International 2017
I.
INTRODUCTION
NANOTWINNED (nt) metals have raised significant attention due to their remarkable electrical conductivity,[1–3] thermal stability,[4,5] and excellent mechanical properties.[6–11] Prior studies show that twin thickness (t), the spacing between coherent twin boundaries (CTBs), plays a significant role in determining their physical and mechanical properties.[12–14] When twin thickness is reduced to a critical value, nanotwins may become unstable as shown by detwinning events occurring under high temperature,[15] electrical field,[16] and mechanical stress.[17] The detwinning behavior is directly correlated to the migration of partials on incoherent twin boundaries (ITBs).[18] According to the experimental studies using high-resolution transmission electron microscopy (HRTEM)[19–21] and atomistic simulations,[22,23] ITBs are composed of groups of Shockley partial dislocations on three successive {111} planes and tend to glide collectively under shear stress,[17,22–25] thereby causing detwinning.[26] There are increasing investigations on radiation response of nt metals,[27–34] and radiation-induced
C. FAN and X. ZHANG are with the School of Materials Engineering, Purdue University, West Lafayette, IN 47907. Contact e-mail: [email protected] JIN LI is with the School of Materials Engineering, Purdue University, and also with the Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3123. ZHE FAN is with the School of Materials Engineering, Purdue University, and also with the Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123. H. WANG is with the School of Materials Engineering, Purdue University, and also with the School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907. Manuscript submitted May 20, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
detwinning has also been observed.[35] Li et al.[28] reported ITB migration in Cu film after Cu3+ ion irradiation, and attributed their migration to the glide of grain boundary Shockley partial dislocations, driven by concurrent reduction in radiation-induced defects. Yu
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