SHEN Feng ,ZHOU Jianqiu ,JIANG Hua

(Institute of Mechanical Engineering, Nanjing University of Technology, Nanjing 210009)

Abstract: Second elastic phases often exist in many nanocrystalline materials. To evaluate the effects of second elastic phase on mechanical behaviors of porous nanocrystalline ceramics, a grain size and porosity dependent mechanical model for porous and multi -phase nanocrystalline ceramics was built in this paper, in which some phases could undergo lastic deformation whereas others may deform only elastically. In this model, each phase was treated as a mixture of grain interior and grain boundary, and pores are taken as a single phase. In conjunction with the secant-modulus approach and isostress assumption, Budiansky's self -consistent method was extended to build a constitutive model for nanocrystalline ceramics with second elastic phases. Further analysis based on the developed model shows that the effects of presence of second elastic phases can affect both the Young's modulus and compressive yield strength of nanocrystalline material significantly, and this sort of effect is dependent on the grain size, hardness and volume fraction of second elastic phase.

Keywords: nanocrystalline ceramics, second phase, yield streng