Deformation behaviour and dynamic recrystallization of AZ61 magnesium alloy

It can be seen that as the strain increased to 0.22, the primary grains were elongated and a mix of fine and coarse grains form a “necklace” microstructure with recrystallized grains at the original grain boundaries. [Display omitted] •Hot compression tests for as-cast AZ61 alloy without annealing were performed.•The apparent activation energy and the strain rate sensitivity were estimated.•The DRX kinetics can be well interpreted by the modified Avrami type equation.•DRX behaviour was investigated with reference to the microstructure observation. The isothermal compression tests with height reduction of 60% for as-cast AZ61 magnesium alloy have been performed with Gleeble-1500 thermo-mechanical simulator at the temperatures of 220, 260, 300, 340 and 380°C and the strain rates of 0.001, 0.01, 0.1 and 1s−1. The true stress–true strain curves were obtained and their characteristics were analyzed. The flow behaviour at elevated temperature can be presented by means of the hyperbolic sine function. The average apparent activation energy and the strain rate sensitivity were determined to be 173.66kJ/mol and 0.13, respectively. The kinetic model of dynamic recrystallization (DRX) was proposed based on the analysis of true stress–true strain data, which revealed the ‘slow–rapid–slow’ evolution of dynamic recrystallized grains with the increase of accumulated strain. Microstructure observation indicated that the volume fraction and average grain size of dynamic recrystallized grains increased with the decrease of Zener–Hollomon parameter. In addition, a good agreement was obtained from the comparison between the experimental and predicted results, which showed that the proposed kinetic model of DRX can give a precise estimate of the dynamic recrystallization behaviour of AZ61 magnesium alloy.