Tailoring bimodal grain structure of Mg-9Al-1Zn alloy for strength-ductility synergy: Co-regulating effect from coarse Al2Y and submicron Mg17Al12 particles
Yongkang Li, Min Zha, Hai-Long Jia, Siqing Wang, Hongmin Zhang, Xiao Ma, Teng Tian, Pin-Kui Ma, Hui‐Yuan Wang
Abstract
Grain boundary strengthening is an effective strategy for increasing mechanical properties of Mg alloys. However, this method offers limited strengthening in bimodal grain-structured Mg alloys due to the difficultly in increasing the volume fraction of fine grains while keeping a small grain size. Herein, we show that the volume fraction of fine grains (FGs, ∼2.5 µm) in the bimodal grain structure can be tailored from ∼30 vol.% in Mg-9Al-1 Zn (AZ91) to ∼52 vol.% in AZ91–1Y (wt.%) processed by hard plate rolling (HPR). Moreover, a superior combination of a high ultimate tensile strength (∼405 MPa) and decent uniform elongation (∼9%) is achieved in present AZ91–1Y alloy. It reveals that a desired bimodal grain structure can be tailored by the co-regulating effect from coarse Al2Y particles resulting in inhomogeneous recrystallization, and dispersed submicron Mg17Al12 particles depressing the growth of recrystallized grains. The findings offer a valuable insight in tailoring bimodal grain-structured Mg alloys for optimized strength and ductility.