Possibilities and prospects for producing silumins with different silicon contents using amorphous microsilica

The main objective of this work is to research complex physical−chemical processes of Al(l)−SiO₂ interface and develop a new technology for producing foundry silumins based on amorphous microsilica obtained from silicon production waste. Effective methods for producing hypoeutectic, eutectic, and hypereutectic silumins using amorphous microsilica were developed. Alloys with a silicon content of 7 wt.% were obtained by blowing preheated amorphous microsilica into the aluminum melt (t=900 °C) along with the stream of argon followed by intense mixing. Alloys with a silicon content of 21 wt.% were manufactured by induction melting of a silicon-containing mixture (60% SiO₂, 40%Al + 20%3NaF·2AlF₃) subjected to the presintering when the amorphous microsilica was reduced to crystalline silicon. It is found that crystalline silicon, which is formed during the roasting of the tableted burden, is smoothly absorbed by the aluminum melt. Aluminum oxide, obtained during the redox reaction, dissolves in cryolite, after which aluminum and silicon are fused together and transferred to the melt. The calculation of the economic efficiency of producing silumins using amorphous microsilica demonstrates a quick project payback period, as well as a high level of its profitability.     

Process−microstructure−properties relationship in Al−CNTs−Al2O3 nanocomposites manufactured by hybrid powder metallurgy and microwave sintering process

Al−2CNTs−xAl₂O₃ nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering process. The correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was measured. It was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite powders. The maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al₂O₃ content of 10 wt.%. Mechanical properties were controlled by Al₂O₃ content, dispersion of nano reinforcements and grain size. The optimum hardness and strength properties were achieved through incorporation of 10 wt.% Al₂O₃ and homogenous dispersion of CNTs and Al₂O₃ nanoparticles (NPs) at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size refinement. Also both longitudinal and shear velocities and attenuation increase linearly by increasing Al₂O₃ content and milling time. The variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al₂O₃ and also less inter-particle spacing in the matrix. The larger Al₂O₃ content and more homogenous dispersion of CNTs and Al₂O₃ NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave.     

转速对2524铝合金搅拌摩擦点焊组织与性能的影响

对2524铝合金薄板进行搭接搅拌摩擦点焊试验, 研究了搅拌头转速对其组织与性能的影响。结果表明, 随转速增加, 焊点外侧飞边越加严重, 组织畸变程度增加, 焊核区宽度增大, 有效连接宽度先增大后减小。母材区硬度最大, 热影响区硬度最低;在焊核区内, 显微硬度随转速增加而增大, 当转速为1 100 r/min时达到最大133.9HV, 而热影响区在300 r/min时硬度最大。在单向拉伸试验中, 接头剪切强度随转速增加先增大后减小, 在700 r/min时达到最大值3 510 N;接头呈现出两种断裂模式: 即低转速下平行于两板面断裂和高转速下沿倾斜方向断裂;断口呈现明显的剪切韧窝形态, 韧窝小而浅, 焊接接头为韧性断裂。     

2A12铝合金在两种体系中微弧氧化膜层的磨损性能研究

目的比较两种不同溶液体系中铝合金微弧氧化膜层的摩擦磨损性能。方法以2A12铝合金为研究对象,通过微弧氧化技术,制备了在两种体系中的微弧氧化膜层。利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)、显微硬度计、摩擦磨损机,研究了两种不同溶液体系中的微弧氧化膜层的形貌、厚度、硬度和磨损性能的差异。结果锆盐体系中膜层的生长速率较磷酸盐中的更大。锆盐和磷酸盐体系中膜层的硬度分别为1050HV和1250HV。锆盐体系的膜层主要由α-Al_2O_3、γ-Al_2O_3、c-ZrO_2和少量的t-ZrO_2组成,磷酸盐体系膜层的主要成分是α-Al_2O_3和γ-Al_2O_3。锆盐体系中,450 V电压下膜层的摩擦系数为0.425,500 V电压下膜层的摩擦系数为0.375;磷酸盐体系中,450 V电压下膜层的摩擦系数为0.328,500 V电压下膜层的摩擦系数为0.325。结论锆盐膜层的摩擦系数总体大于磷酸盐膜层。在磨损过程中,被磨掉的GCr15材料填充到膜层的凹坑中。两种溶液体系下,膜层在高电压下表现出更小的摩擦系数。磨损起始阶段为磨粒磨损,稳定阶段为粘着磨损。     

低压力下环保型络合剂和氧化剂对铝合金化学机械抛光的影响

在低平坦化压力下用壳寡糖(COS)环保型络合剂及H₂O₂氧化剂化学机械抛光铝合金，用原子力显微镜观测抛光后的表面质量，并用X射线光电子能谱仪分析其表面的钝化膜元素，用纳米压痕仪分析钝化膜的力学性能，研究COS及H₂O₂对铝合金CMP的作用机理。结果表明:H₂O₂质量分数为2%时，材料去除率随COS含量的增加而增大，当COS质量分数为0.32%时，材料的去除速率达861 nm/min，表面粗糙度最低为2.50 nm；COS质量分数为0.50%时，材料去除率随H₂O₂含量的增加先增大后减小，当H₂O₂质量分数为1.2%时，材料的抛光去除速率达840 nm/min，同时其表面粗糙度为3.52 nm。加入COS络合剂会在铝合金表面形成主要成分为Al-COS、Al₂O₃和Al(OH)₃的弱钝化膜。      

冷轧预变形对新型铝锂合金的时效析出与力学性能影响

采用大气熔炼铸造及热变形方法制备了Al-4.5Cu-1Li-0.7Mg-1Zn-0.3Ag-0.3Mn-0.2Zr新型铝锂合金板材。通过维氏硬度、拉伸性能、扫描电镜、透射电镜等方法，研究了固溶后不同冷轧预变形量对显微组织和力学性能影响。结果表明，时效前的冷轧预变形量有效促进了新型铝锂基体合金中T1(Al2CuLi)相的析出与均匀分布，减少了θ′(Al2Cu)相的体积分数。冷轧预变形量的增加，缩短了峰时效时间，晶界析出相由连续析出变为非连续析出，无沉淀析出区宽度变小。当冷轧预变形量为15%时，时效态合金的屈服强度与抗拉强度分别达到了668 MPa、690 MPa，延伸率保持在7.9%。     

Study on inhomogeneous cooling behavior of extruded profile with unequal and large thicknesses during quenching using thermo-mechanical coupling model

The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 °C at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.     

铝灰的回收处理及资源化利用研究现状

铝灰是铝工业生产过程中产生的有害固体废物,每年的产生量达到上百万吨。铝灰的大量堆积会引起严重的环境与公共安全问题。铝灰中含有较多的金属铝及其氧化物、氮化物,综合回收利用铝灰对减少环境压力、提升铝行业的经济效益具有重要意义。阐述了铝灰的火法和湿法处理工艺,通过比较得出无盐火法工艺和湿法工艺是值得开发的工艺。介绍了铝灰在耐火材料、陶瓷产品、氢气制备以及工程材料等领域的综合利用现状及研究进展。指出在进一步巩固和发展铝灰原有的高附加值资源化利用的同时,应加强对铝灰处理过程中产生的气体的利用。建议根据铝灰的特性进一步开发新的资源化利用方向。     

改性三氧化二锑协效二乙基次磷酸铝阻燃PA6研究

采用硅烷偶联剂（KH560）对三氧化二锑（Sb₂O₃）进行表面改性处理，并将其协效二乙基次磷酸铝（ADP）应用于聚酰胺6（PA6）阻燃研究。采用傅里叶变换红外光谱和热失重分析对改性Sb₂O₃进行表征，运用垂直燃烧、氧指数、锥形量热仪、热分析以及扫描电子显微镜和拉曼光谱等对阻燃PA6进行了阻燃性能及机理分析。结果表明，改性 Sb₂O₃与Sb₂O₃相比，与ADP具有更好的协同阻燃效应，其作用机制主要是在气相发挥阻燃作用；当ADP含量为8 %，改性Sb₂O₃含量为2 %时，阻燃PA6复合材料的UL 94等级达到V?0级，极限氧指数达到33.8 %。     

铝电解关键指标预测方法的研究与应用

为维持铝电解生产的持续性，保证电解槽的物耗稳定和能耗稳定，通过对铝厂数据的挖掘与建模，提出一整套维持电解槽稳定的策略方法，并用于指导实际生产。首先为数据去噪，针对铝厂数据分布特征未知的特点，提出一种无参自适应的模糊聚类方法，通过迭代自适应得到类簇个数和簇中心；根据聚类结果，将铝厂数据按实际意义标签化，提出一种基于距离的连续属性朴素贝叶斯算法，对分类器使用增量思想，使算法动态分类准确率得到提高；应用单槽测试集数据，通过累积法完成当天各指标等级趋势的预测，确定各指标下变量相对于前一天的变化量，完成预测。实验发现，预测模型可完成铝电解关键指标的预测；提出的聚类、分类算法在UCI数据及铝厂数据上表现良好。