Corrosion behavior of ultrafine-grained AA2024 aluminum alloy produced by cryorolling

The objectives of this study were to produce ultrafine-grained (UFG) AA2024 aluminum alloy by cryorolling followed by aging and to evaluate its corrosion behavior. Solutionized samples were cryorolled to ~85% reduction in thickness. Subsequent aging resulted in a UFG structure with finer precipitates of Al₂CuMg in the cryorolled alloy. The (1) solutionized and (2) solutionized and cryorolled samples were uniformly aged at 160℃/24 h and were designated as CGPA and CRPA, respectively; these samples were subsequently subjected to corrosion studies. Potentiodynamic polarization studies in 3.5wt% NaCl solution indicated an increase in corrosion potential and a decrease in corrosion current density for CRPA compared to CGPA. In the case of CRPA, electrochemical impedance spectroscopic studies indicated the presence of two complex passive oxide layers with a higher charge transfer resistance and lower mass loss during intergranular corrosion tests. The improved corrosion resistance of CRPA was mainly attributed to its UFG structure, uniform distribution of fine precipitates, and absence of coarse grain-boundary precipitation and associated precipitate-free zones as compared with the CGPA alloy.     

高温养护对玻璃粉复合胶凝材料性能的影响

为了研究养护温度对废弃玻璃粉胶凝性能的影响,将废弃玻璃粉取代0、10%、30%、50%的水泥制备复合砂浆;并分别置于常温水域及75℃恒温水域中养护3 d、7 d、28 d、90 d。测试不同龄期的强度。运用活性因子法判别玻璃粉在复合体系中的贡献程度。采用扫描电子显微镜(SEM)分析复合浆体的微观结构。结果表明:高温养护可以促进复合材料水化反应,提高试块的早期强度;但不利于后期强度的发展,在7 d龄期时玻璃粉的贡献度最大。常温养护时,试块早期强度增长较慢,后期强度大幅提升,玻璃粉的活性因子随着龄期的增长而变大。     

高温对活性粉末混凝土抗压强度和热膨胀性能的影响

研究了不同钢纤维掺量的活性粉末混凝土(RPC)高温后的抗压强度和20~800℃温度段内的线膨胀系数,借助TGDSC测试手段对RPC热膨胀性能变化规律进行机理分析。结果表明:随温度升高,RPC抗压强度呈下降趋势,在200℃内下降缓慢;200℃以上下降较快;钢纤维掺量越高,剩余抗压强度越高;线膨胀系数总体呈现先升高后下降的趋势,钢纤维掺量为1%时较素RPC大,钢纤维掺量大于等于2%时较素RPC小。     

漂白粉中固体总钙量的测定

本实验以乙二胺四乙酸二钠(简写为EDTA)络合滴定法对漂白粉中固体总钙量进行了测定。在EDTA的标定试验中,对NaOH的加入量以及钙指示剂(简写为NN)的加入量对实验结果的影响进行了探讨,并确定了最佳实验条件。在固体总钙量的测定实验中,在标定试验确定的最佳实验条件下,又对亚硝酸钠溶液的加入量及静置时间进行了探讨,并确定了最佳实验条件。     

无镍不锈钢17Cr10Mn2MoN的制备与性能

采用气雾化法制备含氮无镍不锈钢粉末，利用热等静压成形并对材料进行固溶处理．热等静压后，材料具有良好的强度、塑性及韧性，抗拉强度为850MPa，屈服强度为505MPa，延伸率为44．5％，断面收缩率为47．5％，冲击功为44J．材料经1100℃固溶处理1h后，塑性和韧性得到进一步提高，延伸率为50．0％，断面收缩率为55．5％，冲击为68J．材料强度和耐蚀性优于316L不锈钢．     

建筑废弃混凝土细粉的活性激发及再利用可行性分析

建筑废弃物细粉中含有大量的未水化的水泥,本实验利用破碎机的除尘系统收集废弃混凝土细粉,使其通过140目的筛(细粉粒径小于0.106 mm),在600℃下进行热处理150 min,激发其活性,使未水化的水泥充分利用,并且替代部分水泥,进行胶砂实验.通过对胶砂强度和流动度分析,证实建筑废弃细粉替代水泥具有可行性.     

利用激光熔覆技术制备ZrO2+MgS辅助电极涂层

利用激光熔覆技术在氧化镁稳定氧化锆(MSZ)固体电解质表面制备出了ZrO2+MgS辅助电极涂层.利用扫描电镜(SEM)和X射线衍射仪(XRD)研究了熔覆层的微观组织，并分析了影响涂层稳定性的因素.研究结果表明，熔覆层与基体结合良好，MgS粉体未完全分解和氧化，因此，利用激光熔覆法在氧化锆固体电解质表面制备ZrO2+MgS辅助电极方法可行.在1600℃时，硫分压大于10-495Pa，MgS不发生分解；氧分压为10-5578Pa时，硫分压大于10-4636Pa，MgS不发生氧化.     

煤层气水平井煤粉产生机理及控制措施

为了揭示煤层气水平井煤粉产生机理,采用理论分析和现场实验的方法,分析了煤层气水平井产出煤粉的质量分数及颗粒粒径变化规律,提出了使用防砂尾管结合油套环空注水稀释煤粉质量分数预防卡泵的措施。研究结果表明:煤层气水平井产出煤粉颗粒粒径呈阶段变化特征,煤粉质量分数超标是导致卡泵停机的主要原因,使用防砂尾管结合井底注水稀释煤粉质量分数措施能有效延长煤层气排采井检泵周期。     

Towards understanding the influence of Mg content on phase transformations in the La3-xMgxNi9 alloys by in-situ neutron powder diffraction study

The present work is focused on the studies of the phase-structural transformations in the La_3-xMg_xNi₉ (x ​= ​1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride (Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction (NPD) at the temperatures ranging from 300 ​K to 1273 ​K using the measurements of the equilibrated alloys at 8 setpoint temperatures of 300, 973, 1073, 1123, 1173, 1223, 1248 and 1273 ​K.Prepared by induction melting initial alloys were found to be multi-phase structured, containing up to 6 individual intermetallic compounds with different stoichiometric compositions. With the increase of the temperature and holding time, various transformations took place in the studied alloys. These included the formations and transformations of super-stacking intermetallics with variable ratios (La ​+ ​Mg)/Ni, 1:3, 2:7 and 5:19.With increasing temperatures, several systematic changes took place. (a) Abundances of (La,Mg)₂Ni₄ AB₂ and (La,Mg)Ni₃ AB₃ type intermetallics gradually decreased before they melted/decomposed above 1073 ​K; (b) The (La,Mg)₂Ni₇ A₂B₇ type intermetallics began to decrease in abundances above 1123 ​K; (c) The transformation in the (La,Mg)₅Ni₁₉ intermetallics from 3R to 2H proceeded above 1223 ​K.The increase of Mg content had no obvious influence on (La,Mg)₂Ni₄ and (La,Mg)₂Ni₇ phases, and corresponding reactions R1 and R3 took place at the same temperatures as in the La–Ni system. However, with increasing Mg content the melting point of (La,Mg)₅Ni₁₉ phase increased while the melting point of the (La,Mg)Ni₃ phase it decreased, leading to the variation of the reaction temperatures of the corresponding processes.The present study will assist in optimizing phase-structural composition of the alloys in the La–Mg–Ni system which contain Mg-modified layered structures by tailoring the high temperature annealing conditions.     

管道工具喷粉线生产调度建模与算法

针对不同品种、不同材质和不同颜色管道工具喷粉生产调度问题, 以生产成本最小化为优化目标, 研究其优化调度方法. 首先, 建立这个问题的混合整数非线性规划模型(MINLP); 其次, 针对该问题设计出相应的贪婪随机自适应搜索算法(GRASP)和遗传算法(GA); 在此基础上, 提出两种算法相集成的GRASP+GA算法. 应用生产实例数据分析比较了这三种算法, 验证了GRASP+GA 算法的优越性.