ABSTRACT
In this study, the effect of Ce additions on microstructure evolution of Mg-7Gd-3.5Y-0.3Zn (wt %) alloys during the casting, homogenization, aging and extrusion processing are investigated, and novel mechanical properties are also obtained. The results show that Ce addition promotes the formation of long period stacking ordered (LPSO) phases in the as-cast Mg-Gd-Y-Zn-Ce alloys. A high content of Ce addition would reduce the maximum solubility of Gd and Y in the Mg matrix, which leads to the higher density of Mg12Ce phases in the as-homogenized alloys. The major second phases observed in the as-extruded alloys are micron-sized bulk LPSO phases, nano-sized stripe LPSO phases, and broken Mg12Ce and Mg5RE phases. Recrystallized grain size of the as-extruded 0.2Ce, 0.5Ce and 1.0Ce alloys can be refined to ~4.3 µm, ~1.0 µm and ~8.4 µm, respectively, which is caused by the synthesized effect of both micron phases and nano phases. The strength and ductility of as-extruded samples firstly increase and then decrease with increasing Ce content. As-extruded 0.5Ce alloy exhibits optimal mechanical properties, with ultimate strength of 365 MPa and ductility of ~15% simultaneously.
ABSTRACT
OBJECTIVE: To determine the impact of a project of building dike for storing water on schistosomiasis transmission in Junshan Lake. METHODS: Junshan Lake in Jinxian County of Jiangxi Province was selected as survey pilot. Data on snail distribution and historical prevalence of schistosomiasis before building dike were collected. The water level inside and outside of the dike was recorded from 1995 to 2002, and the relationship between the water level and snail population at the inside of the dike was analyzed. Survey was made in a natural endemic village to confirm the current endemicity of schistosomiasis. RESULTS: In the selected area of Junshan lake, schistosomiasis was prevalent in 6 villages of 3 townships, with a snail area of 1,394,030 m2 (2,090 Chinese Mu). Snails distributed mainly in the marshland at an elevation of 16.6-17.2 m, and the average infection rate of schistosomiasis in the residents was 12.5% in 1958 before the dike project. In 1960, two years after the dike was built, no living snails were found on the marshland, and the infection rate of schistosomiasis in the residents reduced remarkably. Currently, no schistosomiasis cases were found in human being and cattle in the surveyed village. CONCLUSION: The reservoir project had helped the elimination of snails and interrupted schistosomiasis transmission.