Modelling microstructure evolution during equal channel angular pressing of magnesium alloys using cellular automata finite element method

Michal Zbigniew Gzyl, Andrzej Rosochowski, Andrzej Milenin, Lech Olejnik

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Abstract

Equal channel angular pressing (ECAP) is one of the most popular methods of obtaining ultrafine grained (UFG) metals. However, only relatively short billets can be processed by ECAP due to force limitation. A solution to this problem could be recently developed incremental variant of the process, so called I-ECAP. Since I-ECAP can deal with continuous billets, it can be widely used in industrial practice. Recently, many researchers have put an effort to obtain UFG magnesium alloys which, due to their low density, are very promising materials for weight and energy saving applications. It was reported that microstructure refinement during ECAP is controlled by dynamic recrystallization and the final mean grain size is dependent mainly on processing temperature.
In this work, cellular automata finite element (CAFE) method was used to investigate microstructure evolution during four passes of ECAP and its incremental variant I-ECAP. The cellular automata space dynamics is determined by transition rules, whose parameters are strain, strain rate and temperature obtained from FE simulation. An internal state variable model describes total dislocation density evolution and transfers this information to the CA space. The developed CAFE model calculates the mean grain size and generates a digital microstructure prediction after processing, which could be useful to estimate mechanical properties of the produced UFG metal.
Fitting and verification of the model was done using the experimental results obtained from I-ECAP of an AZ31B magnesium alloy and the data derived from literature. The CAFE simulation results were verified for the temperature range 200-250 °C and strain rate 0.01-0.5 s-1; good agreement with experimental data was achieved.
Original languageEnglish
Pages (from-to)357-363
Number of pages7
JournalComputer Methods in Materials Science
Volume13
Issue number2
Publication statusPublished - 2013
EventComputer Methods in Materials Technology, KOMPLASTECH - Zakopane, Poland
Duration: 13 Jan 201316 Jan 2013

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Keywords

  • cellular
  • severe plastic deformation
  • equal channel angular pressing
  • ultrafine grained metals
  • magnesium alloys
  • modelling microstructure evolution
  • cellular automata
  • finite element method

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