新型倾斜式冷却技术三维数值模拟

自行设计制造了改进的倾斜式冷却技术试验装置,用来制备半固态A1-3%Mg合金坯料.建立了模拟制备半固态A1-3%Mg合金三维分析模型.结果表明:冷却斜板的倾角对合金温度场与速度场分布具有明显影响,出口温度与速度随斜板倾角增大而增大,合金温度沿合金中心线从浇口到出口基本成线性逐渐降低.合金出口温度随着浇注温度的提高而明显升高.为制备具有良好质量的半固态A1-3%Mg合金坯料,倾角θ=45°较合理,浇注温度控制在650℃-660℃的温度范围,不能高于700℃.     

高强韧耐磨钢磨损性能的研究

对高强韧耐磨钢优化成分和热处理工艺后,在MMS-1G高温高速销盘摩擦磨损试验机上进行摩擦磨损性能试验,运用JSM-5610LV扫描电镜分析磨损形貌与速率以及载荷之间的关系和规律.结果表明:在一定载荷(40N)作用下,随摩擦速度的提高,转速对销试样的磨损量影响不大,磨损最先增大后减小;在一定摩擦速度(50m/s)作用下.随载荷的增加,磨损量明显增大.     

高强度合成铸铁微观组织分析

分析了高强度合成铸铁中石墨和基体组织的形成过程,并将其与普通灰铸铁的显微组织进行对比.表明合成铸铁比普通灰铸铁的石墨形状和基体组织都有明显的改善,从而有利于材料综合性能的提高.     

Interface structure and mechanical property of the brazed joint of graphite and copper

A kind of self-made AgCuTiSn braze alloy powder was used to join graphite and copper. The whole brazing process was performed under vacuum circumstances at different temperatures (1033-1193 K) for several holding time (300-1800 s). According to scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electron probe X-ray microanalysis (EPMA) results, the reaction products of the interface are TiC, Ti3Sn, Cu(s. s), Ag(s. s) and Cu-Sn compound. As the brazing parameters increase, the quantity of Ag(s. s) in the braze alloy and C fibers on graphite/AgCuTiSn interface reduce, while that of Cu (s. s) in the braze alloy improves. When the brazing temperature is 1093 K and holding time is 900 s, the joint can obtain the maximum room temperature shear strength 24 MPa.     

Thermal property and microstructure of Al nanopowders produced by two evaporation routes

Al nanopowders with diameters ranging from 20 to 50 nm passivated by Al2O3 coatings were produced by two different evaporation routes: induction heating evaporation (IHE) and laser-induction complex heating evaporation (LCHE). Thermal property of the nanopowders was investigated by differential thermal analysis (DTA) in dry oxygen environment. The results show that Al nanopowders produced by LCHE have the oxidation enthalpy change (ΔH) of 3.54 kJ/g, while the ΔH of Al produced by IHE is 1.18 kJ/g. The phase constitution and microstructures of these nanopowders were revealed using X-ray diffraction (XRD) analysis, transmission electronic microscopy (TEM) and high-resolution transmission electronic microscopy (HRTEM). The results show that the two powders have the same composition and mean particle size, as well as the thickness of Al2O3 coatings (3-5 nm). Defects were observed on the surfaces of the particles by LCHE. However, the defects were not detected by HRTEM on the surfaces of the particles by IHE. The results prove that there exists excessive stored energy in Al nanopowders by LCHE because of the nonequilibrium condition brought by laser and the defects are the storage area of the excessive stored energy. Propellants composed of Al nanopowders by LCHE show higher energy level and specific impulse.     

Thermodynamic properties of stable and metastable phases of Pt metal

Isometric heat capacity cv and isobaric heat capacity cp of Pt with stable and metastable phases were calculated by using pure element systematic theory. These results are in excellent agreement with of SGTE (Scientific Group Thermodata Europe) database and JANAF (Joint Army-Navy-Air Force) experimental values. The calculation results of cv and cp of Pt metal in natural state are in good agreement with those calculated by FP(first-principles) method. It is found that the electron devotion to heat capacity is important to adjust in OA(one-atom) method while calculating heat capacity. The full information about thermodynamic properties of Pt metal with stable and metastable phases, such as entropy(S), enthalpy(H) and Gibbs energy(G) were calculated from 0 K to random temperature. The results are in good agreement with JANAF experimental value. In contrast to SGTE database, the thermodynamic properties from 0 K to 298.15 K are implemented.     

ABAQUS前、后处理模块二次开发的应用

文章以实例说明了Python脚本语言和ABAQUS GUI Toolkit在ABAQUS的前、后处理模块二次开发中的应用,并阐述了不同模块之间的调用流程.通过二次开发程序控制ABAQUS的建模和装配的过程,有效地解决了模型装配时的繁琐、易错等问题,提高了前处理的效率;因ABAQUS对板料拉深进行数值模拟的后处理功能不够全面,为扩展后处理的功能,更好地查看和分析模拟的结果,文章对ABAQUS后处理进行二次开发来达到这一目的.     

钇对AZ91D镁合金盐雾腐蚀行为的影响

利用盐雾法、扫描电镜(SEM)、能谱(EDS)仪和X射线衍射仪等,分析研究钇对AZ91D镁合金在不同浓度的NaCl溶液中的腐蚀规律和腐蚀形貌的影响.结果表明,AZ91D合金的腐蚀速率随着腐蚀时间和NaCl浓度的增加而增大;钇的加入可明显降低合金腐蚀速率,加入1.28%钇的合金的腐蚀随腐蚀时间的延长和介质浓度的增加而呈现先增后减的趋势,合金的耐蚀性达到试验范围的最佳值.合金的腐蚀形貌均表现为不均匀腐蚀,腐蚀产物主要由Mg(OH)2和MgO组成.     

Valence bond structure of Ta-W alloys

The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal(CC)theory.This theory is based on cluster statistics of random alloys.By studying the correlativity between energy and volume of the CC in Ta-W alloys,the valence bond structure of CC is determined by the energy and shape method.Then,following additive law of CC,the valence bond structure of Ta-W alloys is calculated.It is found that the outer shell valence electronic distribution of Ta-W alloys shows ...     

西门子802D系统在C61125车床数控改造的应用

本文介绍利用西门子802D数控系统改造C61125车床的可行性分析,电气参数设置和PLC程序的编制及车床改造后的使用情况。