INVITED: Microstructure evolution in porous metals

E.M. BRINGA

Boston

Congreso; MRS 2012; 2012

MRS

The study of microstructure evolution in materials under extreme conditions is becoming possible thanks to incredible advances in experimental techniques, theory and computer simulation. Atomistic simulations are approaching the length and time scale of some experiments, and I will discuss plasticity in porous materials under compression as an example. In particular, nano-scale plasticity and failure of porous metals under extreme conditions are 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 tension and compression molecular dynamics simulations of Tantalum, as a model b.c.c. metal, with a collection of nanovoids. The effects of high strain rate on the stress-strain curves and on dislocation activity are examined. During loading we find massive total dislocation densities, comparable to recent experimental findings. We also estimate a much lower density of mobile dislocations, due to the formation of junctions. We compare homogeneous loading of our samples with non-equilibrium shock loading-release simulations. In both cases a significant fraction of dislocations survive unloading, unlike what happens in f.c.c. metals, and future experiments might be able to study similarly recovered samples and find clues to their plastic behavior during loading. Comparison to mechanical properties of materials with extremely high porosity (nanofoams) will also be discussed.