Studies on the Quantitative Structure-activity Relationship of Toxicity of Chlorophenol Serial Compounds in the ab initio Methods and Substitutive Position of Chlorine Atom (N_(PCS))

20 Quantum chemical parameters of chlorophenol compounds were fully optimized by using B3LYP method on both 6-31G^＊ and 6-311G^＊ basis sets. These structural parameters are taken as theoretical descriptors, and the experimental data of 20 compounds＇ aquatic photogen toxicity（-lgEC50） are used to perform stepwise regression in order to obtain two predicted -lgEC50 correlation models whose correlation coefficients R^2 are respectively 0.9186 and 0.9567. In addition, parameters of chlorine atom＇s substitutive positions and their correlations （NPCs） are taken as descriptors to obtain another predicted -lgEC50 model with the correlation coefficient R2 of 0.9444. Correlation degree of each independent variable in the three models is verified by using variance inflation factors （VIF） and t value. In the cross-validation method, cross-validation coefficients q^2 of 3 models are respectively 0.8748, 0.9119 and 0.8993, which indicates that the relativity and prediction ability of this model are superior to those of the model obtained by topological and BLYP methods.

Selective Laser Melting of Carbon-Free Mar-M509 Co-Based Superalloy:Microstructure,Micro-Cracks,and Mechanical Anisotropy

In this work,the microstructural evolution,micro-crack formation,and mechanical anisotropy of the selective laser melted(SLM)carbon-free Mar-M509 Co-based superalloy were systematically studied under different linear energy densities(LED).Observation shows that the SLM Mar-M509 superalloy possesses a fully dense structure,whereas some microcracks exist along the building direction.The electron backscatter diffraction results reveal that dominant columnar grains tend to elongate along the building direction parallel to the XZ plane.Meanwhile,both a<001>near fiber texture and a{100}<001>near sheet texture are observed in different specimens.For the specimen with fiber texture,a high misorientation angle exists among different columnar grains,which aggravated the generation of micro-cracks under thermal stress.Higher LED results in higher micro-crack density in the SLM specimen due to higher thermal stress.Mar-M509 specimen fabricated under lower LED exhibits higher tensile strength due to more significant grain refinement.More prominent anisotropy of tensile performance was found in the high LED specimen,which can be attributed to the higher density of micro-cracks and crystallographic texture.Furthermore,the SLM Mar-M509 superalloy exhibits better mechanical properties than the traditional cast technique.In summary,this work can contribute to the development and the future application of SLM-fabricated Co-based superalloy.