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Recovery and recrystallization behaviour of AA5754 and IF-Boron steel during annealing

University of British Columbia

A microstructure model to predict the mechanical properties during annealing has been developed for two important classifications of industrial processed automotive alloys: aluminum-magnesium AA5754 alloy and boron-containing interstitial free steel. The model adopts a rule of mixture to capture the overall softening due to recovery and recrystallization based on the assumption that these two processes proceed independently. The internal state variable approach is employed in the mathematical formulation of the model. The Kuhlmann and Cottrell/Aytekin recovery model and the JMAK recrystallization model are used to capture the time evolution of dislocation density and fraction recrystallized, respectively. The required kinetic parameters are determined from isothermal tests. Isothermal annealing models are developed and validated against data obtained from continuous heating experiments. Experimentally, tensile and hardness tests are carried out in conjunction with quantitative metallography to quantify the kinetics of recovery and recrystallization. The model accurately predicts the microstructural and yield stress evolution in AA5754 under isothermal and non-isothermal annealing conditions. For IF-boron steel, however, the current modelling approach is too simple to capture the complexity involved in the recrystallization process. Consequently, the model for IF-boron steel is considered as purely empirical in nature.

Thesis/Dissertation

application/pdf

2009-08-05

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http://hdl.handle.net/2429/11732

Materials Engineering

University of British Columbia

UBCV

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