Age Hardening Behavior and Mechanism of Gradient-Structured Mg-Gd-Y Alloy Processed by Surface Mechanical Attrition Treatment

Surface mechanical attrition treatment (SMAT) was conducted on a Mg-Gd-Y alloy to obtain a gradient structure. Vickers micro-hardness tests and transmission electron microscopy were employed to study the age hardening behavior and the mechanisms. The result shows that the gradient structure in the SMATed alloy can be classified into three layers: the severely deformed layer, the moderately deformed layer and the undeformed layer. The age hardening behaviors of different layers exhibit distinct difference when aged at 225°C. The peak aging time increases in the order of the severely deformed layer, the moderately deformed layer and the undeformed layer, and the hardness increment at the peak aging increases in the same order. This is attributed to the different distribution of the precipitates and their variable interactions with dislocations in the different layers. The severely deformed layer exhibits the shortest peak aging time and the highest peak aging hardness, which indicates that the surface nanocrystallization has remarkable effect on promoting age hardening for the Mg-Gd-Y alloy. © 2021, Science Press. All right reserved.