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:In paper, recycled Al-1.15Mg-1.02Si-0.7Cu alloy was optical prepared by meiting and casting, the microstructural evolution of the alloy were analyzed by using optical nicroscopy(OM), scanning e!ectron microscopy (SEM), e!ectron back scattered diffraciion(EBSD) and transmission e!ectron nicroscope(TEM),the effects of heal treatment on the mechanical and corrosionlresistant properties of the extruded proUes were invesiigated. The results show that the recrystaliization of the alloy was competed by soiid solution at 550C and fine equaaxaal crystass were obtanned. The iime required for the alloys to reach peak hardness under artificia1 aging cond!tions at 155,175 and 195 C was 18,8 and 4 h, respectively, and the peak hardnesses were 132.96 HV,132. 94 HV and 132.22 HV, respectively, wtth the extruded profiles obtanning the highest tensle strength of 410. 42 MPa and higher elongation of 14. 75% under aging cond!tions at 175 C/8 h. The optimizedsoid solution process ss 550 C/1 hand the artifidal aging process ss 175 C/8 h. The tendency of the alloy to intergranular corrosion ss more pronounced,and the alloy corrodes most severely under peakaged cond!tions, followed by over-aged and weakest underaged. [ABSTRACT FROM AUTHOR]

Atmtng at the problem that brittle Ti-Fe intermetalHc compounds are easily formed tn the additive manufacturing process of titanium/steel composites, which deteriorates the interface properties. In this paper, n^kel (ERN-1)was se!ected as the Interlayer,and the integrated preparation of TC4/309L composites was reaiized by laser fuse additive manufacturing technology. The effect of Ni interlayer addition on the rmcrostructure and properties of the interface was analyzed. The resuits show that "The interface of TC4/309L composites with Ni interlayer Is mainly composed of Fe/Ni interface and Ti/Ni interface. For the Fe/Ni interface,Fe and Ni form an infinite soiid solution, and no obvious defects such as cracks and pores are found, achieving a good metallurgical bonding. The Ti/Ni interface contains TiFe,TiNi3,TiNi,Ti2Ni and other brittle intermetalic compounds,and the maximum hardness of the interface reaches 670. 1 HV. The micro-area tensie test of the interface bondng strength shows that the bonding strength is 30. 5 MPa,and it breaks at the Ti/Ni Interface,showing brittie fracture characteristics. [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

Pearlite is a very important microstructure. Therefore, a model of the ferrite - cementite phase inter- face is constructed in this paper, and the process of nano - intrusion is simulated by molecular dynamics simulation method. By analyzing the mechanical properties and microstructure of the simulation results, the ferrite - ce- mentite phase interface effect was explored. It is found that the indenter load increases with the increase of the distance between the indenter and the grain boundary at different distances (positions of indentation) from the ferrite cementite grain boundary. When the indentation depth reaches a certain depth, the load decreases with the increasing distance. Young's modulus and maximum shear modulus are directly affected by the atomic structure below the indenter tip, and hardness is affected by both the structural integrity and type. The cementite phase interface affects the nucleation, proliferation and expansion of dislocations during the nano indentation process, and the macroscopic performance is the difference of the indenter load at different indentation positions under the same indentation depth. [ABSTRACT FROM AUTHOR]

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]

Additive friction stir deposition (AFSD) is an advanced solid-state additive manufacturing (AM) technology. Compared with traditional melt-based additive manufacturing techniques, AFSD offers several advantages including a dense additive structure, low material deformation, high process efficiency and energy savings. It has extensive applications in aerospace equipment manufacturing, transportation, mechanical manufacturing, and other fields. This paper presents a review of the principles, superiorities, microstructure evolution characteristics, and applications of AFSD technology. The focus is on the current research status regarding the correlation between “process conditions-microstructure-mechanical properties” during the AFSD process, and the mechanical properties of deposited materials are affected by the flow state of materials, interfacial connection mechanism, and microstructural evolution. The applications of the AFSD technology in integral manufacturing of large components, high-performance coatings, and surface defect repair are listed. Finally, the prospects of the AFSD technology are discussed, pointing out that further research and breakthroughs are needed in areas such as coupling of process parameters with microstructural changes, in-situ deformation condition simulation, tool head design, and additive manufacturing of new materials. [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]

This paper introduces the characteristics of lightweight aggregate concrete, analyzes the design method of lightweight aggregate mix ratio, summarizes the research progress of different lightweight aggregate concrete properties affected by various factors at home and abroad in recent years, explores the microscopic representation of lightweight aggregate concrete, points out the existing defects of lightweight aggregate concrete such as poor workability, easy to block pumpability, and gives reasonable suggestions. The future development direction and application prospect of lightweight aggregate concrete are prospected. [ABSTRACT FROM AUTHOR]