A Model of Microstructure Evolution in Metals Exposed to Large Strains
J. Kratochvíla, b, M. Kru v zíkb, c
aCharles University, Faculty of Mathematics and Physics, Sokolovská 83, 186 75 Prague, Czech Republic
bCzech Technical University, Faculty of Civil Engineering, Department of Physics, Thákurova 7, 166 29 Prague, Czech Republic
cAcademy of Sciences of Czech Republic, Institute of Information Theory and Automation of the ASCR, Pod vodárenskou věží 4, 182 08 Prague, Czech Republic
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Crystalline materials at yield behave as anisotropic, highly viscous fluids. A microscopic inspection reveals a structural adjustment of the crystal lattice to the material flow carried by dislocations. The resistance to this flow determines the strength of ductile materials. The deformation microstructure evolves within a common framework up to very high strains >100. To avoid energetically costly multislip, materials are subdivided into regions which deform by fewer slip systems. To maintain compatibility, the regions defined as deformation bands occur in a form of elongated alternately misoriented domains filled with fairly equiaxed dislocation cells. In the proposed continuum mechanics model, the formation of deformation bands of a lamellae type is interpreted as a spontaneous deformation instability caused by an anisotropy of hardening. However, such a model of the bands predicts their extreme orientation and their width tends to zero. This trend is opposed by hardening caused by a bowing stress of dislocations within the cells.

PACS numbers: 02.70.Bf, 61.72.Lk, 02.30.Jr