Optimal design of high-performance rare-earth-free wrought magnesium alloys using machine learning

In this study,a small dataset of 370 datapoints of Mg alloys are selected for machine learning(ML),in which each datapoint includes five rare-earth-free alloying elements(Ca,Zn,Al,Mn and Sn),three extrusion parameters(extrusion speed,temperature and ratio),and three mechanical properties(yield strength[YS],ultimate tensile strength[UTS]and elongation[EL]).The ML algorithms,including support vector machine regression(SVR),artificial neural network,and other three methods,are employed,and the SVR has the best performance in predicting mechanical properties based on the components,and process parameters,with the mean absolute percentage error of YS,UTS,and EL being 6.34%,4.19%,and 13.64%in the test set,respectively.The SVR model combined with multi-objective genetic algorithm are successfully used to optimize mechanical properties of four extruded alloys from Mg-Ca,Mg-Ca-Zn,Mg-Ca-Mn-Sn,and Mg-Ca-Al-Zn-Mn series alloys,respectively,and the corresponding experimental results are in good agreement with the designed ones.Furthermore,new composition schemes are proposed from a wider range of elements and processing features to match the objectives of high-strength,strength-ductility balanced,and high-ductility Mg alloys,and the four-,five-and six-element alloying schemes are provided for the candidates of new-generation wrought Mg alloys.

Two-dimensional interface superstructures assembled by well-ordered solute atoms

Segregation of solutes/impurities in the interfaces plays a decisive role in material performances.However,the segregation of solutes/impurities remains elusive due to the diversity of interfacial structures.Here,in a Mg-Nd-Mn ternary model system,two ordered novel two-dimensional(2D)interfacial superstructures formed by periodic segregation of solute atoms in special symmetric and asymmetric tilt grain boundaries(GBs)have been systematically investigated.Z-Contrast high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)observations provided the atomic-level details on how solute atoms were arranged on these special partially coherent tilt GBs.The strained conditions of each atomic site at the tilt GBs were accurately reproduced by molecular dynamics(MD)simulations plus Voronoi analysis,and the rationality of solute segregation in each atomic-site was evaluated carefully based on the first-principles calculations.These findings expand our knowledge of solute/impurity segregation behaviors in the interfaces,especially the co-segregation behaviors in multi-component materials.

Construction of a biotin-targeting drug delivery system and its near-infrared theranostic fluorescent probe for real-time image-guided therapy of lung cancer

The therapy of non-small lung cancer(NSCLC) is limited by wide metastasis and chemotherapy resistance, herein, we present a new cancer-targeting prodrug PBG with the integration of real-time fluorescence visualization. The potent anticancer drug Gefitinib conjugates a biotin recognition ligand yielding the prodrug PBG via a GSH-activatable disulfide bond linker. Once coupling a near-infrared azo-BODIPY fluorophore into the molecular structure of PBG, we obtain its fluorescent theranostic TBG. The prodrug PBG can sustain Gefitinib release by the high level of GSH in the pathophysiological milieu. We evaluate the drug delivery of the prodrug PBG using fluorescent TBG in PC9 cancer bearing nude mice models,which indicate that TBG can be utilized to monitor the in vivo drug release process. Prodrug PBG can be targeted to accumulate in the cancer lesion with a better and efficaciously therapeutic result compared with the single Gefitinib treatment in cells and in vivo. The fluorescence images also reveal that the targeting accumulation and longitudinal retention of anticancer drug in cancer lesions will contribute to the superior therapeutic effects. The above applications of our new prodrug PBG and its fluorescent theranostic TBG have the potential contribution to the research in biology and the clinical medicine.

The effect of precipitates on the fracture behavior and tensile properties of Mg-14Gd-0.5Zr(wt.%)alloy

The effect of precipitation aging on the fracture behavior of cast Mg-14.23Gd-0.45Zr(wt.%)alloy at room temperature has been studied in this work.Uniaxial tensile and three-point bending tests were conducted on samples peak-aged at 175,200,225,and 250 ℃.Notably,samples aged at 175 ℃ and 200 ℃ exhibited premature fracture during the uniaxial tensile test.Through fractographic observations of the tensile test samples and electron backscattered diffraction(EBSD)analysis on the samples sub-jected to three-point bending tests,a preferential formation of cleavage cracks in samples aged at 175 ℃ and 200 ℃ was identified as the reason for their premature fracture.The X-ray diffraction(XRD)results and transmission electron microscopy(TEM)observations of precipitates indicate that the dominant strengthening precipitates in all peak-aged samples are of theβ'phase,and their size significantly influences the formation of cleavage cracks.This phenomenon is attributed to the shearing mechanism of precipitates.Specifically,the smaller β'precipitates formed under the aging temperature of 175-200 ℃ are susceptible to dislocation shearing,leading to the formation of cleavage cracks.In contrast,the larger size of β'precipitates formed under the aging temperature of 225-250 ℃ provides resistance to shearing,resulting in the restrained formation of cleavage cracks and ultimately contributing to the enhancement of the ultimate tensile strength.