In-situ investigation on the microstructure evolution of Mg-2Gd alloys during the V-bending tests

In this work,the in-situ observation of the microstructure in the Mg-2Gd(wt%)alloys during V-bending tests was operated.The microstructure and texture evolutions were characterized by the in-situ electron backscatter diffraction(EBSD),scanning electron microscopy(SEM)and the high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)technique.The results revealed a unique microcracks nucleation mechanism in the Mg-Gd alloys compared with the traditional Mg alloy(AZ31 alloy).The microcrack was nucleated at the grain boundary for the Mg-2Gd alloy and in the intragranular for the AZ31 alloy during the bending process.This difference mode between the Mg-Gd and the AZ31 alloys was mainly attributed to the more random topology of the grain boundary network,the lower grain boundary cohesion and the enhanced hinder ability for the dislocations due to the segregated Gd atoms in the Mg-Gd alloy.Furthermore,the microcracks that had a large angleθwith the extruded direction(ED)in the Mg-Gd alloys were preferred nucleated since grain boundaries had the larger normal stress during the bending process.