Effect of Al addition on microstructure and mechanical properties of Mg-Gd-Zn alloys

The microstructure evolution and mechanical properties of Mg−15.3Gd−1Zn alloys with different Al contents(0,0.4,0.7 and 1.0 wt.%)were investigated.Microstructural analysis indicates that the addition of 0.4 wt.%Al facilitates the formation of 18R-LPSO phase(Mg12Gd(Al,Zn))in the Mg−Gd−Zn alloy.The contents of Al11Gd3 and Al2Gd increase with the increase of Al content,while the content of(Mg,Zn)_(3)Gd decreases.After homogenization treatment,(Mg,Zn)_(3)Gd,18R-LPSO and some Al11Gd3 phases are transformed into the high-temperature stable 14H-LPSO phases.The particulate Al−Gd phases can stimulate the nucleation of dynamic recrystallization by the particle simulated nucleation(PSN)mechanism.The tensile strength of the as-rolled alloys is improved remarkably due to the grain refinement and the fiber-like reinforcement of LPSO phase.The precipitation of theβ′phase in the peak-aged alloys can significantly improve the strength.The peak-aged alloy containing 0.4 wt.%Al achieves excellent mechanical properties and the UTS,YS and elongation are 458 MPa,375 MPa and 6.2%,respectively.

Cerebral Metabolic Profiling of Hypothermic Circulatory Arrest with and Without Antegrade Selective Cerebral Perfusion： Evidence from Nontargeted Tissue Metabolomics in a Rabbit Model

Background： Antegrade selective cerebral perfusion （ASCP） is regarded to perform cerebral protection during the thoracic aorta surgery as an adjunctive technique to deep hypothermic circulatory arrest （DHCA）. However, brain metabolism profile after ASCP has not been systematically investigated by metabolomics technology. Methods： To clarify the metabolomics profiling of ASCP, 12 New Zealand white rabbits were randomly assigned into 60 min DHCA with （DHCA＋ASCP [DA] group, n = 6） and without （ DHCA [D] group, n = 6） ASCP according to the random number table. ASCP was conducted by cannulation on the right subclavian artery and cross-clamping of the innominate artery. Rabbits were sacrificed 60 min after weaning off cardiopulmonary bypass. The metabolic features of the cerebral cortex were analyzed by a nontargeted metabolic profiling strategy based on gas chromatography-mass spectrometry. Variable importance projection values exceeding 1.0 were selected as potentially changed metabolites, and then Student＇s t-test was applied to test for statistical significance between the two groups. Results： Metabolic profiling of brain was distinctive significantly between the two groups （Q2y = 0.88 for partial least squares-DA model）. In comparing to group D, 62 definable metabolites were varied significantly after ASCP, which were mainly related to amino acid metabolism, carbohydrate metabolism, and lipid metabolism. Kyoto Encyclopedia of Genes and Genomes analysis revealed that metabolic pathways after DHCA with ASCP were mainly involved in the activated glycolytic pathway, subdued anaerobic metabolism, and oxidative stress. In addition, L-kynurenine （P = 0.0019）, 5-methoxyindole-3-acetic acid （P = 0.0499）, and 5-hydroxyindole-3-acetic acid （P = 0.0495） in tryptophan metabolism pathways were decreased, and citrulline （P - 0.0158） in urea cycle was increased in group DA comparing to group D. Conclusions： The present study applied metabolomics analysis to identify the cerebral metabolic profiling in rabbits with ASCP, and the results may shed new lights that cerebral metabolism is better preserved by ASCP compared with DHCA alone.