First Principles Modeling of Metal/Ceramic Multilayer Nano-heterostructures.

Conference · Tue Jul 31 04:00:00 EDT 2012

OSTI ID:1048660

Yadav, Satyesh K ^[1]; Wang, Jian ^[1]; Misra, Amit ^[1]; Liu, Xiang-Yang ^[1]; Ramprasad, Ramamurthy ^[2]

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1. Los Alamos National Laboratory
2. Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA

Nanoscaled multilayer films composed of metals and ceramics have been explored for their potential applications as ductile, yet strong, materials. It is believed that at the nanoscale, the interfaces between the two materials constituting the multilayer assume an increasingly important role in determining the properties, as they comprise a more significant volume fraction of the multilayer with decreasing layer thickness. In this ab initio work, density functional theory was used to calculate the ideal shear strengths of pure Al, pure TiN, the Al/TiN interfacial region, and Al/TiN multilayers. The ideal shear strength of the Al/TiN interface was found to vary from very low (on the order of the ideal shear strength of Al) to very high (on the order of the ideal shear strength of TiN), depending on whether the TiN at the interface was Ti- or N-terminated, respectively. The results suggest that the shear properties of Al/TiN depend strongly on the chemistry of the interface, Al:N versus Al:Ti terminations. Nevertheless, for the Al/TiN multilayers, the ideal shear strength was limited by shear in the Al layer away from the interface, even when the individual layer thickness is less than a nanometer. Further we found an unusual structural rotation of bulk single-crystal Al under uniaxial compressive strains. It was found that under strains either along the <11-2> or the <111> directions, beyond a critical stress of about 13 GPa, the Al crystal can rotate through shear in the Shockley partial direction (i.e.,<11-2>) on the {l_brace}111{r_brace} plane, in an attempt to relieve internal stresses. This phenomenon reveals a possible mechanism leading to the onset of homogeneous dislocation nucleation in Al under high uniaxial compressions.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: DOE/LANL
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1048660
• Report Number(s): LA-UR-12-23372
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERAMICS
CHEMISTRY
DISLOCATIONS
FUNCTIONALS
NUCLEATION
ROTATION
SHEAR
SHEAR PROPERTIES
SIMULATION
STRAINS
STRESSES
THICKNESS