富水粉细砂地层中护壁泥浆材料配比的优化

地下连续墙在以淤泥、粉细砂层地质为主,地下水丰富的江浙沪地区施工时,因传统护壁泥浆携砂能力过剩而造成废浆率大、沉渣厚和成墙质量差等问题。为有效提高地连墙施工质量,开展了低固相地连墙泥浆配制试验研究,通过优选增黏组分、成膜粉体助剂和膨润土,制备匀质性好、滤失量低、泥膜致密和挟沙能力适中的工程用地连墙护壁泥浆,掌握了低固相地连墙护壁泥浆制备工艺等关键技术。基于苏州地铁8号线的工程应用表明:利用该工艺制备的低固相地连墙护壁泥浆沉渣厚度低于100 mm,泥浆循环使用损耗率低于20%,成墙质量得到明显提升。

Forced convection rheoforming process for preparation of 7075 aluminum alloy semisolid slurry and its numerical simulation

A self-developed forced convection rheoforming （FCR） machine for the preparation of light alloy semisolid slurry was introduced. The microstructure characteristics of 7075 aluminium alloy semisolid slurry at different stirring speeds prepared by the FCR process were analyzed. The experimental results suggest that with the increase of the stirring speed, the mean grain size of the semisolid decreases and the shape factor as well as the number of primary grains increase. Meanwhile, the preparation process of semisolid slurry was numerically simulated. The flow characteristics of the melt in the device and the effect of the stirring speed on temperature field and solid fraction of the melt were investigated. The simulated results show that during the preparation process of semisolid slurry, there is a complex convection within the FCR device that obviously changes the temperature field distribution and solid fraction of the melt. When the convection intensity increases, the scope of the undercooling gradient of the melt is reduced and temperature distribution is improved.

Taper barrel rheomoulding process for semi-solid slurry preparation and microstructure evolution of A356 aluminum alloy

The self-developed taper barrel rheomoulding (TBR) machine for light alloy semi-solid slurry preparation was introduced.The semi-solid slurry was obtained from the intense shearing turbulence of the alloy melt in the cause of solidification, which was further caused by the relative rotation of the internal and external taper barrel whose surface contained wale and groove.The heat transmission model of TBR process, the flow rules and the shearing model of the alloy melt were deduced.Taking A365 as experimental material, the microstructure evolution rules under different slurry preparation processes were analyzed.The results show that decreasing the pouring temperature of A365 alloy melt properly or increasing the shearing rate helps to obtain ideal semi-solid microstructure with the primary particle size of about 70 μm and the shape factor of above 0.8.

Semi-solid processing of aluminum and magnesium alloys:Status,opportunity,and challenge in China

Owing to its low cost,short process and low energy consumption,semi-solid processing(SSP)of aluminum(Al)and magnesium(Mg)alloys has been considered as a competitive approach to fabricate complicated components with excellent performance.Over the past decade,significant progress has been achieved in deeply understanding the SSP process,the microstructure and performance of the fabricated components in China.This paper starts with a retrospective overview of some common slurry preparation methods,followed by presenting the performance and the underlying mechanisms of SSP fabricated alloys.Then,the mainstream opinions on the microstructure evolution and rheological flow behavior of semi-solid slurry are discussed.Subsequently,the general situation and some recent examples of industrial applications of SSP are presented.Finally,special attention is paid to the unresolved issues and the future directions in SSP of Al and Mg alloys in China.

Feasibility of semi-solid die casting of ADC12 aluminum alloy

The feasibility of semi-solid die casting of ADC12 aluminum alloy was studied. The effects of plunger speed, gate thickness, and solid fraction of the slurry on the defects were determined. The defects investigated are gas and shrinkage porosity. In the experiments, semi-solid slurry was prepared by the gas-induced semi-solid （GISS） technique. Then, the slurry was transferred to the shot sleeve and injected into the die. The die and shot sleeve temperatures were kept at 180 ℃ and 250 ℃, respectively. The results show that the samples produced by the GISS die casting give little porosity, no blister and uniform microstructure. From all the results, it can be concluded that the GISS process is feasible to apply in the ADC12 aluminum die casting process. In addition, the GISS process can give improved properties such as decreased porosity and increased microstructure uniformity.

Preparation,Structure Characterization and Hydrodesulfurization Performance of B-Ni_2P/SBA-15/Cordierite Monolithic Catalysts

A series of B-Ni2P/SBA-15/cord monolithic catalysts were prepared by coating the slurry of the B-Ni2P/SBA-15 precursors on a pretreated cordierite support, and followed by temperature-programmed reduction in a H2 flow. The samples were characterized by X-ray diffraction （XRD） and N2 adsorption-desorption technique. The catalytic activities for the hydrodesulfurization （HDS） of dibenzothiophene （DBT） were evaluated. The results showed that Ni2P phase was present in all B-Ni2P/SBA-1 5/cord monolithic catalysts. The specific surface areas （SBET） of the B-Ni2P/SBA-15/cord monolithic catalysts was first increased to 167 m2· g-1, and then decreased to 155 m2· g-1 with the increase of boron contents. The catalytic activity also showed the similar trend with the increase of boron contents. The 1.75% （by mass） B-Ni2P/SBA-15/cord monolithic catalysts exhibited the highest DBT conversion of 98.4% at 380 ℃. The cordierite-based monolithic catalysts showed better low temperature sensitivity for HDS of DBT in comparison with the particle catalysts. Moreover, two HDS routes, direct desulfurization （DDS） and hydrogenation （HYD）, proceeded independently over B-Ni2P/SBA-15/cord monolithic catalysts and the main pathway was DDS.

Influence of Sb modification on microstructures and mechanical properties of Mg_2 Si/AM60 composites

The semi-solid antiburning AZ61-1.0%Y magnesium alloy slurry with fine circular solid phase was fabricated by a novel type continuous mechanical stirring in this work.The microstructure of the semisolid slurry was characterized by a metallography microscope.The results show that the fine circular solid phase distributes uniformly in the slurry when the stirring temperature ranges from 600 to 605℃.With the increase of the stirring velocity,the size of the solid phase becomes smaller and smaller.With the increase of the stirring time,the size of solid phase gets finer,but if the stirring time is longer than the critical time,it will be coarsened abnormally.The mechanical properties of semi-solid AZ61-1.0%Y alloy are superior to those of the normally casting magnesium alloy.

The Сoncept of Lava Flow Controlled Use as a Source of Energy and Materials

Our civilization is facing an urgent need to include innovative, large-scale sources of energy and raw materials into its technological cycles. One potential source is magma, which now still inspires awe with its unpredictable power of volcanic eruptions. We propose a method of remote control of lava flow which is based on a special design of a pipe which is lowered into the crater of a volcano. The magma is raised with the help of a well-known method for raising liquids, the airlift. This article includes a detailed description of the structure of the disperser that we shall use to introduce gas into the magma, explains the possible ways to manage the flow of magma, and describes the results that can be achieved. There is potential for the establishment of a whole new industry that will produce cheap electricity, hydrogen, rare metals, fertilizers and innovative construction materials.