Characterization of deformation transition in the rolled LZ91 magnesium alloy under tensile loading

• The rotational activity of α crystals was denoted at 0.6% nominal strain by the integrated intensity of the transmission-XRD measurement. • The dislocations in β phase was observed near the precipitation and the segregated Li region at the nominal strain of 0.6% by the HR-STEM-BF and ACF images. • The depletion of Li in the segregated Li region was discovered near β/β phase at the nominal strain of 0.8% by the EELS measurement. In this study, the mechanical behavior of crystal group of hexagonal close-packed ( hcp ; α phase) and body-centered cubic ( bcc ; β phase) during tensile loading was investigated to elucidate the mechanism from elastic to plastic deformation transition of the rolled LZ91 Mg alloy using transmission-X-ray diffraction (transmission-XRD) measurement, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS). The approximate proof stress of the LZ91 Mg alloy sample was found that the lattice strain retained the expanded state from 0.6% nominal strain, and the transmission-XRD measurement characterized the crystalline behavior during the transition by the integrated intensity of crystal group hcp (100). The lattice strain of bcc (110) decreased from the 0.6% nominal strain due to dislocation activity, which occurred near β/β grain boundary. In addition, we performed the analyses of electron energy loss spectroscopy (EELS) modes, the Li-K peak disappeared from the segregated Li regions of 10–60 nm near β/β grain boundary at the nominal strain of 0.8%. Understanding this mechanical behavior during the elastic to plastic deformation transition by transmission-XRD is crucial for the development of Mg-Li alloys.