基于有限差分法和光滑粒子法的镁合金充型模拟

针对Benchmark件,采用有网格方法(FDM)和无网格方法(SPH)进行充型过程数值模拟,并将模拟结果与WinCast计算结果进行了比对,从而验证了两种方法的有效性和正确性。由于SPH方法可通过追踪粒子的运动得到整个物理系统的特性,无需采用专门方法确定自由表面,在数学模型上具有一定优势。     

基于SPH方法的低压铸造充型过程数值模拟

借助光滑粒子流体动力学(SPH)方法,对所建立的低压铸造充型模型进行了数值模拟,并将模拟结果与Win-cast软件的模拟结果进行对比。结果表明,SPH方法与Win-cast软件模拟结果基本一致,能够较准确地模拟低压铸造充型过程。     

第一性原理研究Al-Y合金在压力作用下的晶胞结构、力学性质、热力学性质和电子结构（英文）

采用基于密度泛函理论的第一性原理研究了压力对Al-Y合金的晶胞结构、力学性质、热力学性质和电子结构的影响。结果表明:晶格常数、弹性常数和弹性模量的计算结果与先前理论计算和实验结果相一致;体模量、剪切模量、杨氏模量、泊松比和德拜温度随压力增大而增大,而热熔则随压力的增大而减小;德拜温度按顺序逐步降低;通过Pugh准则(GB)预测出AlY和Al_3Y相是塑性材料,并随压力的增大塑性增加,而Al_2Y相是脆性材料,其脆性并未随压力增大得到改善;最后还分析了压力对AlY、Al_2Y和Al_3Y相的态密度和电荷布局的影响。     

600MW发电机组凝结水系统变频改造及经济性分析

阐述了华电包头电厂凝结水泵变频改造的方案,通过对凝结水泵节能技术改造的实施,对改造后运行方式及经济性做了详细的分析,为同类型机组实施凝结水节能技术改造提供了科学依据和宝贵经验。     

X65钢在不同温度CO_2酸性溶液中的腐蚀行为

将X65钢放在高压釜内于60～150℃、1 MPa的CO2酸性溶液中进行72 h腐蚀,用XRD、EPMA、SEM和失重法等方法分析了腐蚀产物的形貌、物相组成和腐蚀速率.结果表明:X65钢在60,90,120和150℃的腐蚀速率分别为10.97,3.70,8.37和18.97 mm·a-1;60℃时在腐蚀表面不生成FeCO3保护膜,腐蚀较严重;90℃时生成细小致密的FeCO3保护膜,腐蚀较轻;120℃时生成细小松散的FeCO2保护膜,腐蚀较严重;而150℃时生成粗大不紧密的FeCO3保护膜,所以腐蚀最严重.     

等离子喷涂陶瓷涂层综述

本文综述了利用等离子技术喷涂高性能陶瓷涂层的技术特点和应用情况以及几种热点陶瓷涂层的特性,指出了等离子技术喷涂陶瓷涂层中存在的问题,分析了可行的解决方法。     

Influence of composition and heat-treatment on damping capacity of Cu-Al alloys

The compositions, structures and properties of four kinds of Cu-Al alloys with different constituents were researched by means of optical microscopy, scanning electron microscopy, X-ray diffractometry and damping detection. The structures and properties of Cu-llAl-5Mn-RE experienced different heat-treatment processes were also studied. The results indicate that the damping capacity and microstructure of the alloys are improved by adding Mn and RE elements. Cu-llAl-5Mn-RE obtains the best comprehensive physical performance because of the cooperation of Mn and RE elements. Aging at 200 ℃, the damping capacity gets to the maximum. At 400 ℃, its mechanical property decreases while its damping capacity still remains, indicating its resistance to martensite decomposition and aging at moderate temperature.     

First-principles study on effect of pressure and temperature on structural, elastic, thermodynamic, and electronic properties of Ni3Al alloy

The influence of temperature and pressure on the electronic, elastic, structural, and thermodynamic properties of Ni3Al alloy was investigated by performing a first-principles study. The calculated elastic constants, equilibrium lattice constants, and elastic modulus agree well with the recorded theoretical and experimental data. The calculated elastic constants indicate that C11 is more sensitive than C12 and C44 to pressure. The Young’s modulus, bulk modulus, and shear modulus increase with an increase in pressure. The ratio of bulk to shear modulus (B/G) and anisotropy factor A were also analyzed. The Debye temperature was obtained by calculating the elastic constants, and it changed with the change in the pressure. The thermal expansion coefficient, normalized volume, heat capacity, bulk modulus, and Debye temperature Θ were determined and analyzed by using the quasi-harmonic Debye model at pressures of 0–60 GPa and temperatures of 0–1600 K. Finally, the density of states and Mulliken population were investigated and the effect of pressure on these was analyzed.     

稀土对AZ91镁合金阻燃性和机械性能的影响

针对应用最广的镁铝锌锰系镁合金AZ91,探讨了La的加入对其阻燃性和机械性能的影响.在自制覆盖剂保护下,按照AZ91镁合金化学计量比备料,熔铸了3种不同稀土含量(0,0.2%,0.4%)的样品.对样品进行燃点、硬度测定和金相观察.结果表明,富La稀土不仅可有效地提高镁合金的燃点(在AZ91系镁合金中添加0.4%的富镧稀土可使燃点提高15℃),还可细化晶粒,显著提高了镁合金的硬度,合金的布氏硬度由不含稀土时的548.8 MPa提高到656.6 MPa.     

TiAIN涂层的研究和应用进展

0前言 近年来,在经济全球化的背景下,出现了新一轮的国际专业化分工,使我国的制造业获得了空前高速发展的机遇,而制造业的发展,离不开切削刀具,现代切削刀具更成了提升制造业技术水平的关键因素之一。在切削加工领域,高速、高效、高精密加工受到空前重视,干式切削刀具的发展成果显著,耐热、耐磨及润滑性能优异的复合涂层大量出现。