Study of hot forging behavior of as-cast Mg-3Al-1Zn-2Ca alloy towards optimization of its hot workability

Mg-3Al-1Zn-2Ca (AZX312) alloy has been forged in the temperature range of 350-500 degrees C and at speeds in the range of 0.01-10 mm s(-1) to produce a rib-web shape with a view to validate the processing map and study the microstructural development. The process was simulated through finite-element method to estimate the local and average strain rate ranges in the forging envelope. The processing map exhibited two domains in the following ranges: (1) 350-450 degrees C/0.0003-0.05 s(-1) and (2) 450-500 degrees C/0.03-0.7 s(-1) and these represent dynamic recrystallization (DRX) and intercrystalline cracking, respectively. The optimal workability condition according to the processing map is 425-450 degrees C/0.001-0.01 s(-1). A wide flow instability regime occurred at higher strain rates diagonally across the map, which caused flow localization that should be avoided in forming this alloy. The experimental load-stroke curves correlated well with the simulated ones and the observed microstructural features in the forged components matched with the ones predicted by the processing map. (C) 2014 Elsevier Ltd. All rights reserved.