Study of age hardening in a Mg-2.2Â wt%Nd alloy by in situ synchrotron X-ray diffraction and mechanical tests

Microstructure evolution of a supersaturated solid solution Mg-2.2 wt%Nd alloy during aging at 240 °C for 6 h (stage I), at 295 °C for 3 h (stage II), and finally at 320 °C for 1 h (stage III) was studied by in situ synchrotron X-Ray diffraction. In stage I, diffraction from β1 (Mg3Nd, FCC) precipitates was observed after ~ 15 min. Evolution of the volume, size, and aspect ratio of β1 with the aging time were estimated from peak intensity and peak width analysis. In stage II, diffraction from β (Mg12Nd, tetragonal) precipitates was observed after ~ 36 min while β1 remained in the material. In stage III, the volume of β1 reduced substantially in relative to β. The identified precipitation sequence from the in situ aging experiment is supported by ex situ electron microscopy observations. β′, which had not been detected by synchrotron X-rays, was additionally found using transmission electron microscopy in the material by the end of aging stage I. Tension and hardness tests using specimens with different aging conditions were further performed to understand how different precipitates affect the strength and ductility of the Mg-Nd alloy.