High Strain Rate Behavior of Nanoporous Tantalum

CARLOS RUESTES; EDUARDO BRINGA; ALEXANDER STUKOWSKI ; JOAQUIN F. RODRIGUEZ NIEVA; GRACIELA BERTOLINO; YIZHE TANG; MARC A. MEYERS

Boston

Congreso; APS MARch Meeting 2012, of The American Physical Society; 2012

APS

Nano-scale failure under extreme conditions is not well understood. In addition to porosity arising from mechanical failure at high strain rates, porous structures also develop due to radiation damage. Therefore, understanding the role of porosity on mechanical behavior is important for the assessment and development of materials like metallic foams, and materials for new fission and fusion reactors, with improved mechanical properties. We carry out molecular dynamics (MD) simulations of a Tantalum (a model body-centered cubic metal) crystal with a collection of nanovoids under compression. The effects of high strain rate, ranging from 107 s-1 to 1010 s-1 , on the stress strain curve and on dislocation activity are examined. We find massive total dislocation densities, and estimate a much lower density of mobile dislocations, due to the formation of junctions. Despite the large stress and strain rate, we do not observe twin formation, since nanopores are effective dislocation production sources. A significant fraction of dislo-cations survive unloading, unlike what happens in fcc metals, and future experiments might be able to study similar recovered samples and find clues to their plastic behavior during loading.