Strengthening Ni alloys with nanoscale interfaces of negative excess energy

The strength of nanograined and nanotwinned metals is limited
by the inherent instability of grain or twin boundaries below a
length scale of typically about 10 nanometers. From experimental
and density functional theory calculations, we found that the
coherent interfaces between face- centered- cubic and
hexagonal- close- packing lattices with a negative excess energy
were more stable than twin boundaries in supersaturated Ni(mo)
solution. The negative excess- energy interface can be produced
at extremely high density in Ni(mo) solution with average
spacing as small as about 1 nanometer, which inhibits plastic
deformation and elevates the strength close to the theoretical
value of the alloys. The measured Young’s modulus of the Ni(mo)
alloys increases obviously with the interface density, reaching
254.5 gigapascals, well above that of the same compositional
metallic glass and intermetallic compound (Ni3mo).