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The price of alloying element Bi is low, and it has a high solid solubility in magnesium, and with the decrease of temperature, its solid solubility decreases, and the Mg3 Bi2 phase is precipitated, which improves the mechanical properties of magnesium. Therefore, Mg-Bi alloys have good solution and aging hardening potential. The addition of Sn, Mn, Al, Ca, Zn and other elements to Mg-Bi alloy can modulate the alloy microstructure and further increase the mechanical properties and corrosion resistance of the alloy. In this paper, the research progress of Mg-Bi alloys was introduced, and on the basis of summarizing the research achievements of Mg-Bi binary alloys, the microstructure and properties of Mg-Bi-Sn alloys, Mg-Bi-Mn alloys, Mg-Bi-Al alloys, Mg-Bi-Ca alloys, and Mg-Bi-Zn alloys were systematically summarized, and the effects of alloying on the second phase, grain size, texture and dynamic recrystallization of alloys were reviewed. The effects of alloying element types, addition amounts and hot working parameters on the mechanical properties of alloys were described, and the future research is prospected. The existing problems in the study of Mg-Bi alloys were summarized, and the future research was prospected. [ABSTRACT FROM AUTHOR]

Geopolymer not only possesses the combined excellent properties of organic polymer materials, ceramic materials and cement materials, but also has many advantages such as low production energy consumption and carbon emissions, wide raw material source, and excessive consumption of solid wastes. Therefore, it has rapidly become a research hotspot in the field of inorganic cementitious material in recent years. After introducing the calcium component into geopolymer system, the interaction processes among the main gel phases may become more complicated. Moreover, microstructure and the main performance of geopolymer may be greatly affected. In this paper, we systematically review the research developments in Ca_containing geopolymer, with a particular summary and analysis on the way of introducing calcium component during geopolymer preparing process, as well as the influence rule and action mechanism of calcium component on microstructure and performance (including setting time, compressive strength, solidification/stabilization of heavy metals, resistance to chemical attack, al kali - aggregate reaction, thermal stability, and resistance to efflorescence) of geopolymer. Tt would provide technical reference for performance control and application study of C

The graphite conductive phase material is used to replace the fine aggregate to prepare the functional conductive concrete, and the concrete matrix can be heated by electricity heating to achieve the purpose of snow melting and ice melting. Resistivity is the main index to measure the electrical conductivity of concrete, which is easily affected by factors such as concrete moisture content and ambient temperature. Tn this paper, graphite, graphite ore and graphite tailings were used as conductive phases to prepare conductive concrete. The mechanical properties of three kinds of graphite conductive phase concrete, the resistivity evolution law and microscopic properties of graphite concrete under different temperatures and water contents were studied, and the conductive mechanism of graphite concrete was analyzed. The results show that the increase of conductive phase content, temperature and water content reduces the resistivity of concrete, and the incorporation of conductive phase reduces the resistivity most significantly. Tn addition, the results of SEM and EDS tests showed that the content of carbon in the concrete matrix increased significantly under different dosage conditions, which verified that the addition of graphite materials could promote the electrical conductivity of concrete, but it would cause holes and micro-cracks in the concrete matrix, which had an adverse effect on the strength of graphite concrete. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites prepared via in-situ synthesis technology weigh the contradiction between strength and plasticity, which is expected to realize the integration of structure and function of aluminum matrix composites. In-situ synthesis of TiB2 particles reinforced aluminum matrix composites has high specific stiffness and modulus, excellent mechanical properties, corrosion resistance, wear resistance and fatigue resistance, which is one of the research hotspots of metal matrix composites in recent years and has broad application prospects in automobile manufacturing, highspeed trains, aerospace and national defense and military fields. In this paper, the characteristics and advantages of three reaction systems, Al-K2TiF6-KBF4 system, Al-TiO2 B2 O3 system and Al-Ti-B system, for in-situ synthesis of TiB2 particles reinforced aluminum matrix are summarized, the research status of the influence of TiB2 particles on the grain size, interfacial bonding and wettability of aluminum matrix is summarized, and the mechanism of TiB2 particles reinforced aluminum composites is discussed. The unsolved problems in this field are summarized, and the potential development space of TiB2 particles reinforced aluminum matrix composites prospected, so as to provide reference for the research and development of in-situ synthesized particles reinforced aluminum matrix composites. [ABSTRACT FROM AUTHOR]