Corrosion behavior of under‐, peak‐, and over‐aged 6063 alloy: A comparative study

The mechanical property of age‐hardenable Al‐alloys is governed by the state of ageing, which determines the microstructure and consequently, their corrosion behavior which is a vital aspect for a number of applications. This article presents a comparative assessment of corrosion behavior of under‐, peak‐ and over‐aged Al‐Mg‐Si alloy. Corrosion characteristics have been determined via immersion tests in 0.1 M ortho‐phosphoric acid solution and intergranular corrosion (IGC) tests. Corroded surfaces are examined by field emission scanning electron micrographs‐energy dispersive spectroscopy and 3D optical profilometer. The obtained results reveal that the corrosion rate at a specific immersion time as well as the depth of IGC increases in the order for under‐, peak‐, and over‐aged states. Irrespective of the state of ageing, corrosion loss increases linearly but the rate of corrosion decreases rapidly with increasing immersion time. The dominant mode of corrosion in under‐aged alloy is identified as localized pitting, while peak‐aged is highly susceptible to IGC in contrast extensive pitting corrosion is observed for over‐aged alloy. The observed differences in corrosion behavior are explained considering characteristics of precipitates. Formation of β (Mg₂Si) in case of over‐aged alloy and presence of inclusions like AlFeMnSi particles are found to accelerate pitting corrosion.     

FCC油浆提高废胶粉改性沥青热存储稳定性试验

废胶粉用FCC油浆进行预处理后用于沥青改性,制备出沥青与胶粉间相容性好、高温存储性能稳定的胶粉改性沥青.考察并得出相关工艺条件,同时应用多种评价手段分析改性后沥青的性能,结果表明,预处理后胶粉改性沥青的高温存储性能稳定,低温时柔韧性、抗开裂性能明显提高,高温时稳定性、抗车辙能力及弹性回变性能增强,沥青粘弹区间明显变宽.     

浇筑式沥青混凝土心墙型式改进的建议

本文根据浇筑式沥青混凝土主、副心墙材料的性能，分折了沥青混凝土心墙施工或运行中破坏的原因，建议用编织一无纺复合布取代预制块，以避免主、副心墙材料变形性能相差悬残对心墙运行的不利影响，从而发挥浇筑式沥青混凝土心墙的优越性。     

复合乳化沥青的粘附性试验方法研究

鉴于目前使用的阳离子乳化沥青粘附性试验方法难以有效评价复合乳化沥青粘附性，通过试验研究并综合考虑乳化沥青施工和路用实际情况，提出了乳化沥青水煮法试验方法和采用该方法检验复合乳化沥青粘附性时的评定标准。     

N.m.r. line shape-relaxation correlation analysis of bitumen and oil sands

The first results of the analysis of bitumen and oil sands using the recently developed n.m.r. spingrouping technique are presented. The n.m.r. relaxation experiments were carried out on bitumen, and on natural and dried oil sands samples. The results indicate that the spin-grouping can resolve and quantify several components of the samples studied. The bitumen and bitumen fraction of the oil sands are resolved according to their spin-spin relaxation times into three major groups: solid-like (rigid), solid-like (mobile) and semi-liquid. The water in the oil sands exists in two different environments. Tentatively one environment is assigned to be the bridges between the sand grains, while the other is assigned to be the clay surface. One can conclude that with spin grouping of complex mixtures the decomposition (in which components are resolved according to their dynamic state) is possible. The accuracy of such resolution is of the order of a few per cent.     

An inverse solution methodology for estimating the diffusion coefficient of gases in Athabasca bitumen from pressure-decay data

An inverse solution methodology is developed for the estimation of diffusion coefficient of gases in highly viscous, oil-sands bitumens from isothermal, pressure-decay measurements. The approach involves modeling the rate of change in pressure using the diffusion equation for the liquid phase coupled with a mass balance equation for the gas phase. The inverse solution framework is utilized to arrive at two graphical techniques for estimating the diffusion coefficient. Both techniques involve the determination of the slope of a straight line resulting from plotting the experimental data in accordance with the developed model. An advantage of the proposed techniques is that the diffusion coefficient is estimated directly, i.e. without making it an adjustable parameter. The novelty of the proposed method is in its simplicity as well as its ability to isolate portions of the pressure-decay data affected by experimental fluctuations. The effect of the initial pressure on the predicted diffusion coefficient and pressure-decay profile was also investigated. The diffusion coefficients of CO₂, CH₄, C₂H₆ and N₂ in Athabasca bitumen at 50–90 °C and about 8 MPa were estimated and compared with literature values.     

Determination of gas dispersion in vapor extraction of heavy oil and bitumen

In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier.     

泡沫沥青混合料动态性能研究

为更好地模拟泡沫沥青混合料在车辆动载作用下的动态性能，便于与国外相关研究进行比较，采用劈裂法对混合料动态性能进行研究。通过试验研究骨料类型、级配、水泥用量等对泡沫沥青混合料动态回弹模量的影响，总结了泡沫沥青混合料动静模量的关系。     

遵义后坝奥陶系红花园组油苗岩石轻烃特征分析

遵义后坝奥陶系红花园组生物碎屑灰岩中发现油苗和沥青,经过气/源岩、沥青/源岩对比,震旦、寒武及奥陶系产层轻烃C₆₊₇结构组成基本一致,奥陶系含油苗灰岩轻烃星图与震旦系泥岩、寒武系沥青砂岩星图较为相似,显示红花园组油苗主要来源于震旦系和下古生界过成熟或高成熟海相烃源岩,油气经历了较长距离的运移,得以在奥陶系中保存下来。这对评价该地区油气前景有重要意义,预示着可能存在一套特殊的含油气组合,存在以O₁h古风化壳储集层为目的层的勘探领域。在兴文—叙永一线以西地区现今下古生界储盖组合保存良好,在适当的构造圈闭中可形成油气藏。志留系和二叠系产层轻烃C₆₊₇与震旦系、寒武系及奥陶系等产层轻烃C₆₊₇明显有别,星图对比性差,表征它们之间成烃母质或沉积环境均有不同。      

论老年教育的地位、作用和发展方向

老年教育在社会中具有重要的地位和作用。它是终身教育的重要组成部分,是社会发展的客观需要,是解决老龄问题的重要途径和方法。探讨了随着社会经济的发展和老龄化社会进程的加快,在21世纪老年教育的发展方向。