摘要
For metal nanofilms composed of nanocrystals,the multiple deformation mechanisms will coexist and bring unique and complex elastic-plastic and fracture mechanical properties.By successfully fabricating large quantities of uniform doubly-clamped suspended gold(Au)nanobeams with different thicknesses and nanograin sizes,we obtain full-spectrum mechanical features with statistical significance by combining atomic force microscopy(AFM)nanoindentation experiments,nonlinear theoretical model,and numerical simulations.The yield and breaking strengths of the Au nanobeams have a huge increase by nearly an order of magnitude compared with bulk Au and exhibit strong nonlinear effects,and the corresponding strong-yield ratio is up to 4,demonstrating extremely high strength reserve and vibration resistance.The strong-yield ratio gradually decreases with decreasing thickness,identifying a conversion of the failure type from ductile to brittle.Interestingly,the Hall–Petch relationship has been identified to be still valid at the nanoscale,and K in the equation reaches 4.8 Gpa·nm1/2,nearly twice of bulk nanocrystalline Au,which is ascribed to the coupling effect of nanocrystals and nanoscale thickness.
基金
supported by the National Natural Science Foundation of China(NSFC)(No.51971070)
the National Key Research and Development Program of China(No.2016YFA0200403)
Eu-FP7 Project(No.247644)
CAS Strategy Pilot Program(No.XRA 09020300).
