Julio Esteban Méndez Durán

This study investigates, for the first time, the effect of cryogenic rolling on the microstructure and mechanical behavior of Mg–Zn–Y alloys containing long-period stacking-ordered (LPSO) phases. Two compositions, Mg ₉₇ Zn ₁ Y ₂ and Mg ₉₅ Zn ₂ Y ₃ (at.%), were processed by cryogenic rolling after a previous hot rolling step. Scanning electron microscopy revealed significant fragmentation of the LPSO phases, with particles smaller than 1 µm homogeneously distributed within the matrix. X-ray diffraction analysis using the Williamson–Hall method showed an increase in microstrains, indicating a higher crystal defect density induced by cryogenic deformation. These microstructural changes resulted in notable improvements in hardness, with Vickers microhardness increasing by 16.8% in the Mg ₉₇ Zn ₁ Y ₂ alloy and by 14.5% in Mg ₉₅ Zn ₂ Y ₃ , compared to their respective hot-rolled states. The enhancement in mechanical properties is attributed to the fragmentation and homogeneous distribution of the LPSO phase particles, which act as effective barriers to dislocation motion, thus contributing to an increase in defect density. Importantly, no precipitation of secondary phases was detected, confirming the stability of the LPSO phases during cryogenic processing. These results demonstrate that cryogenic rolling represents a promising processing route for strengthening Mg–Zn–Y alloys with LPSO structures.

Commercially pure aluminum (Al) was refined through the addition of the Al-5Ti-0.25C master alloy, resulting in the formation of Al₃Ti and TiC phases, which serve as refining agents. Open-cell metallic foams were successfully produced using the replication casting technique, with pore sizes ranging from 1.00 to 3.35 mm. For the infiltration process, refined aluminum was used, while unrefined aluminum served as a baseline reference. The resultant foams underwent multiple annealing cycles at 480 °C, with the most refined and homogeneous microstructure observed after 504 h. Comprehensive microstructural characterization was conducted utilizing scanning electron microscopy and optical microscopy. Additionally, uniaxial compression tests were performed to generate stress–strain profiles for the foams, facilitating an assessment of their energy absorption capacity. The findings indicated an enhancement in energy absorption capacity by a factor of 2.4 to 3, which can be attributed to the incorporation of Al-5Ti-0.25C and the subsequent annealing process.