Abstract
It is of great importance to study how the process parameters influence the continuum flow properties and mesomicrostructural features during friction stir welding (FSW) of titanium alloys. In the present paper, microstructure evolution of dynamic recrystallisation (DRX) was simulated by cellular automaton method based on metal plastic flow analysis. The established model can accomplish multiscale modelling of macroscopical plastic flow behaviour, mesostructural dislocation activities, microstructural grain growth dynamics and finally mechanical property of the FSW joint. The predicted flow stress curves are similar with that experimentally measured. Influences of strain rate and temperature on the evolution of the average dislocation density (equivalent to flow stress) as well as the final grain size are analysed, which are in good agreement with classic DRX theories. Final grain size results from the contrary effect of strain rate and temperature, while the strain rate with higher gradient in the welded joint has greater influence. According to the prediction result, a lot of options can be made on matching of marching speed and rotation speed to maintain refined microstructure.
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