Mechanical tests on small-volume materials show that in addition to the usual attributes of strength and ductility,the controllability of deformation would be crucial for the purpose of precise plastic shaping.In our present work,a"mechanical controllability index"(MCI)has been proposed to assess the controllability of mechanical deformation quantitatively.The index allows quantitative evaluation of the relative fraction of the controllable plastic strain out of the total strain.MCI=0 means completely uncontrollable plastic deformation,MCI=∞means perfectly controllable plastic shaping.The application of the index is demonstrated here by comparing two example cases:0.273 to 0.429 for single crystal Al nanopillars that exhibit obvious strain bursts,versus 3.17 to 4.2 for polycrystalline Al nanopillars of similar size for which the stress-strain curve is smoother.
Prof.Shan Zhiwei’s group at Xi’an Jiaotong University discovered a novel mechanism for room temperature plastic deformation in magnesium(Nature Communications,2014,5:3297).Magnesium and its alloys have been intensively studied for several decades due to their potential applications in automobile and aerospace industry.Deformation twinning and dislocation slip are known to
