Role of Mn Addition in Tuning the Microstructure and Mechanical Properties of Mg-Al-Ca Dilute Alloy

In this work, the role of manganese (Mn) addition in tuning microstructure and mechanical properties of the Mg-1.0Al-0.4Ca-xMn (x = 0.6, 1.0, 1.34 wt.%) alloys are studied. When enhancing the Mn content from 0.6 to 1.0 wt.%, the nano-precipitates of Al2Ca/Al8Mn5 phase becomes much finer, which can effectively refine the dynamical recrystallized (DRXed) grain size and also the subgrain lamellae. However, further increasing Mn content to 1.34 wt.%, the amounts of nano-Al2Ca and Al8Mn5 phases in the grain interiors are obviously decreased since more Al atoms are attracted to form the micron-sized Al8Mn5 phases, and average DRXed grain size in AXM102 alloy is thus largely increased. As a result, the as-extruded Mg alloy can exhibit the optimal mechanical property with yield strength (YS) of ~ 379 MPa and elongation of ~ 7.6%, only when the added Mn atom is controlled at ~ 1.0 wt.%. The relevant results can shed light on the further designing of novel high-strength and low-alloyed Mg wrought alloys.