Radiation resistance and mechanical response of materials in extreme environments
Development of energy-efficient and safe technologies for energy production, transportation, and defense poses ever-increasing demands on materials stability in harsh environments. Ceramics are attractive in this regard because of their high-temperature stability, good corrosion and radiation resistance, and excellent mechanical strength. This talk will be focused on fundamental issues related to stability of ceramics and intermetallics in extreme environments. First, I will discuss the role interfaces play in response to radiation and corrosion. I will demonstrate that in ceramics, the effects of interfaces are closely coupled to the complex defect energy landscape, leading to surprising new phenomena. For example, we discovered that even though ceramics form line compounds, radiation causes segregation of constituent elements to grain boundaries without precipitating new phases, which impacts corrosion resistance. Secondly, I will discuss response of materials to mechanical stresses and high-velocity impact and our recent discovery of new mechanisms of ductility in nominally brittle materials. We found that in the absence of dislocation plasticity, stress-induced amorphous shear bands can increase ductility and toughness. We identified criteria for when such shear bands enable plasticity instead of being pre-cursors to fracture. These mechanisms open the possibility for design of materials that are both strong and ductile.
