Corrosion-erosion resistance of Zn-Al co-cementation coatings on carbon steels in aqueous media

A novel Zn-Al co-cementation coating was obtained by a pack cementation method,This coating possesses a two-layered structure,The outer layer is mainly composed of Fe2Al3 and FeAl intermetallics with a small amount of Zn,and the inner layer consists of Zn,Fe and a small amount of Al.The corrosion-erosion resistance of Zn-Al con-cementation coatings on carbon steel was studied by a rotary corrosion method in various NaCl and H2S containing solutions and relevant SiO2 containing media,The experimental results are compared with those of carbon steels and the sherardizing and aluminizing coating ,showing that the Zn-Al co-cementation coating have excellent corrosion-erosion resistance in various aqueous media.     

铝合金局部加压凝固及流动数值模拟的研究

局部加压方法是压铸中用于消除铸件厚壁处缩孔缺陷的一种新工艺.本研究通过实验模型测量了不同加压条件下铸件的冷却曲线,分析了局部加压引起的凝固变化.考虑局部加压引起的补缩流动,通过适时修改网格文件、初始和边界条件的方法,模拟了局部加压过程中铝合金的凝固及流动变化,并与实验结果进行了对比,二者基本吻合.     

铈对中铝耐热铸铁抗氧化性能的影响

采用氧化增重法测定了含Ce中铝耐热铸铁在850℃时氧化动力学曲线，用SEM，X－ray对氧化膜表面的形貌，结构及氧化层－基体界面进行了观察分析，结果表明：Ce改变了中铝耐热铸铁氧化膜的结构和组成，提高了中铝耐热铸铁的抗氧化性能。     

CYCLIC DEFORMATION OF COARSE GRAINED POLYCRYSTALLINE PURE Al——Ⅱ.FRACTURE SURFACE MORPHOLOGY

SEM photos for very coarse grained and high ductile polycrystalline pure Al show followingcharacteristics:A few fracture sources are concentrated,the crack propagates in fan-shapenear them,and the fatigue striations are cyclic cleavage facets.Each striation consists of awide cleavage facet and a narrow cleavage stage.Those stages often blunt due to plasticdeformation.The fatigue striations are clear and continual,and distribute over whole zone ofstage Ⅱ crack propagation.Two kinds of fatigue striations form in different levels,areconjoined by a“twisted baked piece of pastry”band.The secondary crack along the fatiguestriations was observed frequently.Some of them have already developed into secondarymacrocracks and secondary fatigue striations were found clearly on secondary fracture sur-face.The fracture surface can be divided into two parts,initiation and propagation zone of thecrack,however,no statical-fracture zone was observed.The mechanism to form striationswas preliminarily discussed.     

MICROSTRUCTURE STUDY OF CONSTITUENT PHASES IN 2024 SERIES Al ALLOYS

X-ray microanalysis,convergent beam electron diffraction(CBD)and selected area electrondiffraction(SAD)studies on the structures and compositions of the constituent phases in2024 series Al alloys have been conducted.Partial substitution of alloying elements is found tooccur in all the constituent phases,which cause small deviations from the stoichiometric com-positions reported in these ternary compounds.The dominant phase is α-Al_(12)(FeMn)_3Si whichhas a body center cubic crystal structure with the Im■ space group and a=1.25 nm.The nextdominant phase is Cu_2FeAl_7 which has a primitive tetragonal crystal structure with theP4/mnc space group and a=0.6336 nm,c=1.487 nm.The minor phase is α'-Al_(12)Fe_3Si hav-ing α primitive cubic crystal structure with the Pm■ space group and α=1.27 nm.     

空冷淬火Cu-Zn-Al合金马氏体结构及稳定化现象

利用Ｘ射线衍射强度分析、透射电镜观察、相变点测量等方法研究了空冷淬火态Ｃｕ１８Ｚｎ１４Ａｌ合金马氏体结构及其稳定化现象。认为该合金空冷淬火可获得长程有序完全的Ｍ１８Ｒ马氏体，其有序组态为Ａｌ原子与Ｃｕ原子、Ｚｎ原子与Ｃｕ原子两种近邻（ｎｎ）有序（Ｋ＝偶，Ｈ＋Ｋ／２＝奇），以及产生Ｋ＝奇的衍射中Ａｌ原子与Ｚｎ原子次近邻（ｎｎｎ）有序。其基面原子分布为：Ⅰ—１４２５Ａｌ＋１１２５Ｃｕ、Ⅱ—Ｃｕ、Ⅲ—１８２５Ｚｎ＋７２５Ｃｕ。与此相对应，该合金相应为Ｈｅｕｓｌｅｒ结构。该合金在充分有序化的条件下仍存在马氏体稳定化。     

Ca1-3x/2Al2Si2O8:xEu3+荧光粉的发光和光温传感特性

为了探究稀土离子掺杂铝硅酸盐的光温特性,本文采用燃烧合成法制备了系列荧光粉材料Ca_1-3x/2Al₂Si₂O₈:xEu³⁺。X射线衍射结果表明掺杂Eu³⁺离子不会改变基质CaAl₂Si₂O₈的晶体结构。荧光光谱结果表明该荧光粉在近紫外光区域具有较强吸收,当被波长为393 nm的近紫外光激发后,其最大特征发射峰为611 nm,且Eu³⁺离子的最佳掺杂浓度为0.05。利用上升时间测温法研究了CaAl₂Si₂O₈:Eu³⁺荧光粉的光温传感特性,结果表明:随着Eu³⁺掺杂浓度的增加,上升时间单调递减,但当掺杂掺杂超过0.100时就会发生淬灭。Ca_0.985Al₂Si₂O₈:0.01Eu³⁺的相对灵敏度随温度的升高先增大后减小,并在520 K时达到最大值（0.024 K^-1）。上述研究表明该荧光粉具备优异的温度传感性能,在测温领域具有广泛的应用前景。     

温度对CaO-SiO2-Al2O3-MgO高炉渣系Al2O3活度的影响

 Al₂O₃作为熔渣中的主要组元之一,其对熔渣的冶金性能的影响尤为突出。对于高炉炼铁而言,高炉渣中Al₂O₃增加会对炼铁及脱硫造成不利影响。然而,随着中国钢铁工业的不断发展,相对低廉的高Al₂O₃进口铁矿石使用量不断攀升,使得高炉渣中Al₂O₃含量明显增加,高炉渣中Al₂O₃质量分数往往大于15%,更高的甚至大于20%。目前关于高Al₂O₃高炉渣系中Al₂O₃组元的热力学性质(例如采用参考渣法测定Al₂O₃的活度)及其对炉渣冶金性能的影响等研究鲜有报道,而温度是影响冶金熔渣冶金性能的重要热力学因素之一,因此探讨温度对冶金熔渣中Al₂O₃组元活度影响的规律不仅具有重要的研究意义,同时也为现场实践提供坚实的理论依据。采用参考渣法对1 773～1 873 K温度条件下CaO-SiO₂-Al₂O₃-MgO高炉渣系Al₂O₃活度进行测定,并采用Raman光谱对熔渣的结构进行检测。考察了温度对CaO-SiO₂-Al₂O₃-MgO高炉渣系Al₂O₃活度的影响。结果表明,随着温度的增加,熔渣中Al₂O₃的化学势降低,熔渣与铜金属熔液之间的反应向右移动来达到新的平衡,因而Al₂O₃的活度随着温度的增加逐渐降低。温度的增加使熔渣中Al₂O₃与碱性金属氧化物发生反应,使钙铝酸盐(CaO·Al₂O₃和CaO·2Al₂O₃)和镁铝酸盐(MgO·Al₂O₃)等复合物生成量增加,此时熔渣的结构由于O2-的增加而逐渐发生解聚,熔渣中的自由Al₂O₃减少,从而导致Al₂O₃活度逐渐降低。     

高铝高炉渣系的熔化特性

 为了掌握高Al₂O₃条件下(w(Al₂O₃)为15%以上)高炉渣系的熔化特性,利用差式扫描量热仪分析了不同w(MgO)/w(Al₂O₃)、碱度(R)以及w(Al₂O₃)对高铝高炉渣的熔化温度及熔化热的影响。试验结果表明,炉渣熔化开始温度为1 248～1 291 ℃、熔化结束温度为1 432～1 485 ℃、熔化热为137～211 J/g;当w(Al₂O₃)=15%、高w(MgO)/w(Al₂O₃)时,发生了共晶逆反应,导致高炉炉渣熔化开始温度逐渐降低,但由于高炉炉渣的液相线温度基本未变,所以炉渣熔化结束温度基本未发生改变;w(Al₂O₃)为20%时,随着w(MgO)/w(Al₂O₃)的增加,炉渣中易生成熔点较高的镁铝尖晶石,导致高炉炉渣熔化开始温度逐渐增大,与此同时,炉渣液相线温度逐渐降低,导致炉渣熔化结束温度逐渐降低;随着碱度R的增加,高炉炉渣中生成了具有高熔点的化合物、炉渣的液相线温度升高,使得高炉炉渣的熔化开始温度逐渐增加、炉渣熔化结束温度逐渐升高;随着w(Al₂O₃)的增加,发生了共晶逆反应,故炉渣的熔化开始温度逐渐降低,而随着w(Al₂O₃)的增加,炉渣中键能较大的Al—O键增多,需要在更高温度下才能实现炉渣的最终熔化,即熔化结束温度逐渐增加;随着w(MgO)/w(Al₂O₃)、R以及w(Al₂O₃)的增加,炉渣熔化热逐渐增多。分析认为,随着R的增加,炉渣中有高熔点化合物的生成,熔化热增加;随着炉渣中w(Al₂O₃)的增加,炉渣中Al—O键增多,解聚破坏熔渣结构消耗的热量增多;而随着w(MgO)/w(Al₂O₃)增加,高熔点化合物的生成或熔化开始温度降低,造成熔化热增加。     

SiC含量对SiCp/Al复合材料摩擦性能的影响

采用粉末冶金技术制备了SiC_p/Al复合材料,探讨了SiC颗粒质量分数对SiC_p/Al复合材料密度、布氏硬度、微观形貌以及摩擦磨损性能的影响。结果表明,SiC颗粒表面形成了少量可提高界面结合性的Al₄C₃化合物。随着SiC质量分数增加,SiC_p/Al复合材料的密度没有明显的变化,当SiC质量分数增加至25%时,密度明显下降。SiC_p/Al复合材料的布氏硬度随着SiC质量分数的增加呈先增长后减小的变化趋势。当SiC质量分数为20%时,材料的硬度最优（HBW 114）,平均摩擦系数达到最大值（0.3425）,摩擦后试样表面形貌平整且犁沟较浅,SiC颗粒未出现明显剥落。