A Dislocation-based Multiscale modeling of Strength and Ductility of Materials with Gradient Microstructure


Dr. Hao Lyu
Institute I-General Materials Properties, FAU

Wednesday, 27.06.2018, 17:00
WW8, Raum 2.018, Dr.-Mack-Str. 77, Fürth


Decreasing the grain size into nano-scale can effectively enhance the strength of material. However, the expense of superior strength is paid by  substantial reduction of the ductility, which is considered as the 'heel  of  Achilles' for nanocrystalline metal. Recent experimental works have shown that materials with certain gradient microstructures can overcome the strength and formability trade-off dilemma, using specific processing such as severe plastic deformation and heterogeneous lamellar ecrystallization,  SMAT etc. The grain size  in such microstructures ranges from a hundred nanometers to tens of micron meters. Therefore, to study the macroscopic behavior of  this type of 'Multiscale' microstructure, a dislocation-‐based multi-scale framework is employed, which  includes  a  continuum  dislocation  dynamic  (CDD)  model,  stress/strain  gradient model  and  Visco-Plastic Self-‐Consistent (VPSC) model. The simulation results were compared with experimental  data. The  break-down of Hall-Petch as observed  and a new interpretation of grain  size  effect  with  considering  spatial gradient  of  grain  size  is proposed.