Precipitation strengthening represents a crucial strengthening approach in the realm of metals, with particular significance for magnesium. In this study, a complex LPSO–precipitate structure, which is constituted of the principal secondary phases in Mg rare earth (RE) alloys, namely the Long-Period Stacking Ordered (LPSO) phase and the aging precipitate, was successfully fabricated within a Mg-11Y-1Al alloy. Subsequently, an in-depth investigation was conducted regarding the interaction between dislocations and this LPSO–precipitate structure under varying temperature conditions. The findings revealed that, at room temperature (RT), the aging precipitates effectively hindered the movement of basal dislocations, and the activation of non-basal dislocations is rather difficult, resulting in the alloy’s high strength and low plasticity. When the temperature was elevated to 200 °C, although non-basal slip could be initiated, the LPSO–precipitate structure was capable of blocking both basal and non-basal slips. Consequently, the alloy still demonstrated high strength and low plasticity. As the temperature further increased to 250 °C, dislocations could cut through the aging precipitate particles, and the interior of the grains could provide partial deformation. Hence, the tensile elongation of the alloy was significantly enhanced, increasing from 4% to 12% as the temperature was elevated from 200 °C to 250 °C. These results suggest that the LPSO–precipitate structure still exerts a remarkable strengthening effect at 200 °C. When the temperature reaches 250 °C, the plasticity of the alloy is improved but its strength decreases. The research outcomes presented in this paper offer a novel perspective for the precise tailoring of mechanical properties through precipitation strengthening within Mg-RE alloys.

Welding is widely employed in manufacturing processes, with the mechanical properties of welded joints being a primary focus of welding technology research. However, distinct regions of welded joints—including the base metal (BM), heat-affected zone (HAZ), and deposited metal (DM)—exhibit divergent deformation behaviors, which collectively influence the fracture behavior of the joints. In this study, the specific locations of strain concentration and fracture in GH3535 alloy welded joints (fabricated using ERNiMo-2 welding wire) were investigated during tensile tests at room temperature (RT) and 700 °C. Characterizations were performed via digital image correlation (DIC), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Results revealed that during RT tension, strain was concentrated in the deposited metal adjacent to the fusion line (FL) which is 200% higher than BM, where cracks also initiated. At 700 °C, strain was mainly concentrated in the deposited metal, where the maximum strain concentration was approximately three times that in the base metal, and fracture also occurred in this region. It has been confirmed through in-suit observations that during high-temperature deformation, the deposited metal of the GH3535 alloy is more prone to strain concentration and simultaneously exhibits lower plasticity. This study advances the understanding of the deformation behavior of GH3535 alloy welded joints through in-suit observation results, and indicates that strengthening the deposited metal (i.e., the region more prone to strain concentration) is a more effective approach to improve the mechanical properties of such welded joints.