engleski

New way to take control of a structural grain size in the formation of nanomaterials by extrusion

Production of nanomaterials by formation of extreme plastic deformation ECAP (Equal-Channel Angular Pressing) is one way to prepare of nano-structures of engineering materials by multiple extrusion of materials into a neck area of sample tube with a rapid change in direction of loading and loading. Grain refinement and a structural grain diameter reduction at nano size can be achieved in this way while acting under extremely high pressures SIGecap [MPa] where there is an increase in the tensile strength SIGm [MPa], yield strength SIGkl [MPa] and the elastic modulus Emat [MPa] by reducing the elongation Ataņ [%], because of the implicit function (SIGm, Emat, SIGkl, Ataņ ...)=f(dzrnoi, Kplmati). There is a confrontation of our method of calculating with previously used calculations for granularity dzrno [μm according to the Hall-Petch relation. The confrontation of theoretical results show a close match and simultaneously prove that it is a physical-mechanical reciprocity and superposition resolution in relation to a so called neutral zone of deformation. Custom analytical solutions can be applied to solve a problem of determining stress SIGecap [MPa], respectively of extrusion force Fecap [N] to achieve a desired grain size. However this role has not been yet solved, because of previously used equations are being derived only on the basis of a geometry of system which do not provide adequate results. The extrusion of sample is therefore being performed in multiple cycles, is getting more expensive, is being extended, and an immediate state of material shall be governed only by a subjective estimation and technologist experience.

nanomaterials; extreme plastic deformation; control; loading; grain diameter reduction

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