Microcompression study of Al-Nb nanoscale multilayers
- PDF / 363,493 Bytes
- 7 Pages / 584.957 x 782.986 pts Page_size
- 30 Downloads / 198 Views
Arief Suriadi Budiman, J. Kevin Baldwin, Nathan A. Mara, and Amit Misra Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory (LANL), Los Alamos, New Mexico 87545
Seung Min Hana) Graduate School of EEWS, Korea Advanced Institute of Science and Technology, Yuseong Gu, Daejeon 35-701, Republic Korea (Received 30 June 2011; accepted 6 October 2011)
Microcompression tests were performed on the Al/Nb multilayers of incoherent interfaces with the layer thicknesses of 5 nm Al/5 nm Nb and 50 nm Al/50 nm Nb. The Al-Nb multilayers showed increase in strength as the layer thickness was reduced; the average flow stresses at 5% plastic strain from the 5 nm Al/5 nm Nb and 50 nm Al/50 nm Nb layer thickness specimens were determined to be 2.1 GPa and 1.4 GPa respectively. The results from this Al-Nb microcompression study were compared with those of the previous report on Cu-Nb multilayer microcompression results that indicated that the flow stresses of the Al-Nb multilayer are lower than those of Cu-Nb with the same bilayer spacing. The observed difference in strength was attributed to a potential difference in the interfacial strength of the two incoherent multilayer systems.
I. INTRODUCTION
Recently, there have been extensive studies in the development and characterization of nanolayered metallic multilayer systems.1–16 The metallic multilayers are known to exhibit ultra high strengths due to the effective constraint of the dislocation movements, and the strength has been shown to depend on the bilayer spacings.8–15 Therefore, the metallic multilayer systems have a key advantage in being able to control the strength by controlling the bilayer spacings: the smaller the layer spacing, the higher the strength. The controllable, ultra high strength of the metallic multilayers have potential usage in the automobile and aerospace applications, where high strength-to-weight ratio is desired. The deformation mechanism that is responsible for the high strength of the multilayers is dependent on the bilayer spacings. For the bilayer spacings in the range of micrometers, the conventional hardening mechanism from dislocation pile-up at the interfaces occurs. In this regime, the Hall-Petch effect has been identified as the strengthening mechanism, where r } h1/2 (r is the stress a)
Address all correspondence to this author. e-mail: [email protected] This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/. DOI: 10.1557/jmr.2011.414 592
J. Mater. Res., Vol. 27, No. 3, Feb 14, 2012
and h is the layer thickness).6–9,15–18 However, as the bilayer spacing is reduced to a range of tens of nanometers, the deformation mechanism changes to a single dislocation bowing or a confined slip of a single dislocation.19–23 In this regime, the stress needed to drive the confined dislocation forward is inversely proportional to the layer thickness h (r } 1/h). In res
Data Loading...
