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32. Research on strengthening mechanism of AZ63 cast magnesium alloy based on precipitation phase orientation control.

Author

Ruan, Shihui, Yang, Mingbo, Wang, Haijun, Li, Yan, Cheng, Renju, Zhou, Yongfeng, and Jiang, Linxi

Subjects
TENSILE strength, HEAT treatment, ULTRASONICS, NUCLEATION, ALLOYS
Abstract

A high strength and toughness AZ63 cast magnesium alloy whose ultimate tensile strength, yield strength and elongation at room temperature respectively reached 319 MPa, 160 MPa and 7.6%, was developed by combining the alternating-temperature ultrasonic melt treatment and T6 heat treatment. The high as-aged tensile properties of the alloy with the alternating-temperature ultrasonic melt treatment are mainly attributed to the remarkable increase of the β-prismatic precipitates with orientation relationships (ORs) of ( $ \bar{3}\bar{3} $ 3 ¯ 3 ¯ 0)β // (1 $ \bar{1} $ 1 ¯ 00)α, [ $ \bar{1} $ 1 ¯ 11]β // [11 $ \bar{2} $ 2 ¯ 0]α, thereinto the mentioned-increase is possibly related to that the solute-vacancy clusters along {0 $ \bar{1} $ 1 ¯ 11} plane might serve as the nucleation points of the β-prismatic precipitates. [ABSTRACT FROM AUTHOR]

Published
2024
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44. Multiple geochemical parameters of the Wuliying well of Beijing seismic monitoring networks probably responding to the small earthquake of Chaoyang, Beijing, in 2022.

Author

Chen, Yuxuan, Liu, Guiping, Huang, Fuqiong, Wang, Zhiguo, Hu, Leyin, Yang, Mingbo, Sun, Xiaoru, Hua, Peixue, Zhu, Shijun, Zhang, Yanan, Wu, Xiaodong, Wang, Zhihui, Xu, Lvqing, Han, Kongyan, Cui, Bowen, Dong, Hongyan, Zhou, Yonggang, Barbera, Marcella, and Lopes, Fernando

Subjects
EARTHQUAKE magnitude, EARTHQUAKE prediction, WATER table, HYDROGEN isotopes, WATER-rock interaction, TRACE elements
Abstract

Hydrological changes in groundwater coupled with earthquakes had been documented in previous studies by global researchers. Although few reports investigate multiple geochemical parameters that respond to earthquakes, trace elements received less attention, whereas they were suggested to be more sensitive to small earthquakes than the commonly used geochemical parameters. Beijing is located in the Zhangjiakou-Bohai(Zhang-Bo) seismic belt of North China, and although the occurrence of small earthquakes is frequent, the great historic earthquake in the Sanhe-Pinggu area M8 in 1679 in the adjoining southeast of Beijing gained widespread public attention. To find effective precursors that are significant for operational earthquake forecasting of the Beijing area, we carried out a one year test research project through weekly collection of groundwater samples during June 2021 to June 2022 from the seismic monitoring well of Wuliying in northwest Beijing. The 41 trace elements chemical compositions were analyzed for each sample. During the project ongoing period, the biggest earthquake with a magnitude of ML3.3 occurred in the Chaoyang District of Beijing on 3 February 2022. The content changes in these trace elements were systematically monitored before and after the earthquake. Through retrospective research, it was found that a few sensitive trace elements were anomalous to be coupled to the earthquake, including Li,Sc, Rb, Mo, Cs, Ba, W, U, Sr, Mn, Ni,andZn. In addition to trace elements, we examined stable isotopes of hydrogen and oxygen and the existing hydrological data on groundwater level, temperature, major ions, and gases to assess the validity of geochemistry as a monitoring and predictive tool. We only found that F(fluorine) ions and He (helium) gas had apparent shifts related to the earthquakes, while no shifts in the groundwater level were observed. Such characteristics of multiple geochemical parameters indicate that trace elements are likely to be more sensitive to crustalstrain than the groundwater level and major ions. We assumed a most likely mechanism of the combination of mixing and water-rock interactions to explain the phenomenon. The probable scenario was that minor stresses caused by the earthquakes might create microcracks in bedrocks, thereby leading to a small volume of chemically distinct water mixing with the original water of the aquifer, and finally, the earthquakeinduced rock fractures enhance the water-rock interactions, resulting in the post-seismic recovery of trace elements and δ180 value migration to the GWML. More testing works to find other sensitive sites to investigate multiple geochemical characteristics aiming at long-term to short-term earthquake prediction in the Beijing area and Zhang-Bo seismic belt are in progress. [ABSTRACT FROM AUTHOR]

Published
2024
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