Atomic-scale investigation of the aperiodic precipitates in the Mg-Zn based alloys
The atomic configuration of aging precipitates is the key to improving the strength of alloys,and understanding the atomic structural details of precipitates would help to better design high-strength alloys.Here,the atomic configurations of aperiodic precipitates in peak-aged Mg-Zn (-Al ) series alloys are systematically investigated employing aberration-corrected high-angle annular dark-field scanning transmission electron microscopy ( HAADF-STEM) combined with selected area electron diffraction( SAED) techniques.The results show that the rod-like phase precipitated by isothermal aging in the Mg-8Zn binary alloy are multidomain structures with Laves characteristics,which are assembled by the 72° rhombus structures and 72° equilateral hexagon structures in the [0001]α basal plane.Additionally,it is found that the aging precipitation behaviors of the Mg-8Zn alloy can be significantly altered with the addition of Al,and two kinds of aperiodic precipitates formed in the Mg-8Zn-4Al binary alloy have thus been confirmed.One is a bulk precipitate phase formed by the self-adaptive assembly of structural units assembled by 36° rhombus,72° rhombus,and 72° equilateral hexagon,whose pseudo 10-fold axes are fully parallel to the [ 0001]α zone axis.Another one is also a rhombus-shaped three-dimensional icosahedral quasicrystal phase,whose 5-fold axis is completely parallel to the [0001]α.This atomistic information of aperiodic precipitates in the Mg-Zn(-Al) series alloys not only leads to new insights into the structure and formation mechanism in the condensed matters but also provides theoretical guidance for the design of high-strength ZK and AZ series Mg alloys.
万方数据
维普
