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Mechanical and Civil Engineering Seminar

Friday, May 20, 2016
11:00am to 12:00pm
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Gates-Thomas 135
High temperature mechanical performance of metallic and metal-ceramic nanoscale multilayers
Javier LLorca, Professor, Department of Materials Science, Polytechnic University of Madrid,

Nanoscale multilayers or nanolaminates are nanostructured materials made up by alternating layers of two or more materials with a layer thickness below ~100 nm. Different layered combinations can be found (metal-metal, metal-ceramic and ceramic-ceramic) offering unique mechanical, optical, magnetic and electronic properties suitable for applications as irradation-resistant materials in nuclear engineering, tribological coatings, high performance capacitors for energy storage, integrated circuit interconnects, data storage and X-ray optics. In all these cases, the thermo-mechanical properties of the multilayers constitute a key factor, either from the functional perspective (protective coatings or nuclear materials) or from the reliability viewpoint (integrated circuit interconnects or optical coatings).

These nanolaminates present outstanding mechanical properties at ambient temperature in terms of strength, toughness and fatigue resistance as well as excellent thermal stability [1]. Their unique properties are mainly a result of the high density of interfaces, which change the standard mechanisms of deformation and fracture when the layer thickness is below ~100 nm. Nevertheless, their high temperature mechanical properties have been unknown until the recent experimental development of high temperature nanomechanics.

In this talk, the mechanisms of deformation and fracture are studied in detail as a function of temperature by means of high temperature nanoindentation and micropillar compression in three different nanoscale multilayer systems (Cu/Nb, Zr/Nb and Al/SiC). The influence of the interface character, diffusion, oxidation as well as the thermal activation of plastic deformation mechanisms on the mechanical properties of each system was ascertained. This information is critical for the design of novel metal-metal and metal-ceramic nanolaminates with enhanced mechanical properties under different regimes [2-3].

[1] J. M. Molina-Aldareguía, I. Martín-Bragado, J. LLorca. Thin Solid Films, 571 (2014) 245-246.

[2] S. Lotfian, M. Rodríguez, K.E. Yazzie, N. Chawla, J. LLorca, J. M. Molina-Aldareguía. Acta Materialia, 61 (2013) 4439-4451.

[3] M. Monclús, S. J. Zheng, J. R. Mayeur, I. J. Beyerlein, N. A. Mara, T. Polcar, J. LLorca, J. M. Molina-Aldareguía, APL Materials, 1 (2013) 052103.

For more information, please contact Jenni Campbell by phone at 626-395-3389 or by email at jenni@caltech.edu.