Scale-up of processing techniques and production of bulk nanostructured materials have been a challenge for industrial application. Sample size, ductility, and thermal stability of ultrafine-grained and nanocrystalline materials are major concerns in this regard. Several processing routes were developed to synthesize ultrafine-grained and nanocrystalline metals and alloys, and major drivers for these efforts are optimization of processing parameters and tailoring microstructural features that contribute to mechanical properties and thermal stability.

Top-down synthesis techniques (such as ball milling, high pressure torsion, equal channel angular pressing, surface mechanical attrition treatment, and accumulative roll bonding) are, in some cases, limited in grain-refinement capability. Bottom-up synthesis techniques (such as inert gas condensation and electrodeposition) are typically limited in small sample sizes. Furthermore, thermal stability is an outstanding concern in all ultrafine-grained and nanocrystalline materials. Therefore, besides the sample size issue, there has been always a trade-off between the grain refinement limit that is related to processing routes, ductility that is inversely related to grain size, and thermal stability that is highly susceptible in high energy boundaries in nanostructures.

The goal of this special issue is to address breakthroughs in optimization of processing parameters for production of bulk ultrafine-grained and nanocrystalline metal and alloys. Novel processing techniques will be addressed in this regard. Tailoring the nanostructural features will be of interest for publication and potential topics include, but are not limited to:

• Processing techniques for production of bulk ultrafine-grained and nanocrystalline metals and alloys
• Improving mechanical properties via alloys design and microstructure refinement
• Study of microstructural features (deformation and growth twins, dispersion particles and precipitates, dislocations and vacancies, etc.)
• Characterization techniques: Electron microscopy, Electron backscattered diffraction, and Raman spectroscopy
• Thermal stability

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/jnm/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: