Abstract
In the present study, we investigated the dynamic precipitation (DP) of Mg17Al12 phase accompanying dynamic recrystallization (DRX) during the deformation of an Mg-Al-Zn-RE alloy. Hot compressions at various strains, strain rates and temperatures were followed by microstructural characterization via scanning electron microscope (SEM) and energy-dispersive X-ray spectroscope (EDS). The precipitation during heating and holding was avoided by proper treatment to guarantee initial microstructures without Mg17Al12 phase. During hot compression, the DP of Mg17Al12 particles with blocky shape accompanies the DRX process and mainly occurs on the DRXed grain boundaries. The volume fraction, number density and average size of Mg17Al12 precipitates depend on both temperature and strain rate, while the influence of temperature is more prominent for volume fraction. Phenomenological models bridging the number density and average size of precipitates with deformation conditions (temperature and strain rate) were established and validated. The pinning effect of DP on the grain growth makes DRXed grain size deviate from the values predicted by the classical function of the Zener-Hollomon parameter. Influenced by the sensitiveness of the pinning effect, temperature makes more sense in trimming DRXed grain size than strain rate. Vickers hardness tests were also conducted after hot compression. The influence of DP on microhardness lies in its effect on grain refinement.
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