Lath-like phases formed at an extremely high temperature in a Mg-RE(RE=rare earth)-Al alloy

Thermal stable intermetallic particles are important for the heat resistance of magnesium(Mg)alloys.In this work,many lath-like particles formed in α-Mg grains of a Mg-8Gd-3Sm-0.7Al casting alloy when heat-treated at 873 K.Atomic-resolution high-angle annular dark field scanning transmission electron microscopy(HAADF-STEM) characterizations indicate that most of them are Mg-containing Al_(2)(Gd,Sm),with the atomic ratio of Mg:Al:(Gd,Sm) being ~1:1:1;a small part of them with relatively wider thickness are long-period stacking ordered(LPSO) phases simultaneously containing both 14H and 18R structures.Both followed common orientation relationships with Mg matrix as those reported in previous work.In addition,many Mg laths were observed in the primary blocky Al_(2)(Gd,Sm) phase at grain boundaries,where the atomic ratio of Al:(Gd,Sm) in the Al_(2)(Gd,Sm) matrix was 2:1.Finally,density functional theory(DFT) calculations illustrated the detail structure of the re-constructed Mg/Al_(2)RE interface and simultaneously deduced the underlying reason for the re-dissolution of the newly formed Mg-containing Al_(2)(Gd,Sm) plates in α-Mg matrix.

Influence of Allelochemicals on Microbial Community in Ginseng Cultivating Soil

Objective To study the influence of allelochemicals such as benzoic acid, diisobutyl phthalate, diisobutyl succinate, palmitic acid, and 2,2-bis-（4-hydroxyphenyl） propane on the microbial community of ginseng cultivating soil. Methods Soil samples were sprayed with five allelochemicals（100 mg/L） and their mixture（20 mg/L）, respectively. Carbon metabolic ability variances were analyzed by Biolog method and genetic polymorphism variance was analyzed by RAPD method. The Nei＇s genetic diversity index and Shannon＇s information index were calculated. Results Significant differences in carbon metabolic activity were found between allelochemical-treated soils and control. Further analysis indicated that although the carbon-utilizing ability and genetic polymorphism of soils treated with di-isobutyl phthalate, di-isobutyl succinate, and allelochemical mixtures were lower than those of the other treatments, genetic similarities of soils treated with di-isobutyl phthalate, diisobutyl succinate, and allelochemical mixtures were much higher than those of the other treatments. Conclusion Allelochemicals significantly declined the genetic diversity and carbon metabolic activity of microorganisms in newly reclaimed forest soil for ginseng cultivation.