Buffering effects on electrograining of aluminium in nitric acid

Electrograining of a binary Al-Si alloy has been undertaken in nitric acid based electrolytes, with the resultant surfaces examined by scanning and transmission electron microscopies. Depending on electrograining conditions, the pit appearance varies from hemispherical to large lateral pits, with the latter favoured in relatively acidic electrolytes. The conditions prevailing in the pit have been explored through use of aluminium ion additions to the nitric acid electrolyte as well as additions of species which influence the precipitation and dissolution of aluminium hydroxide. These confirm that control of the pit solution pH, through hydroxide generation, as a result of the selected electrograining conditions and consequent anodic and cathodic polarisation, enables tailoring of the resultant electrograined surface appearance.     

Comparison of the A.C. electrograining of aluminium in hydrochloric and nitric acid

Homogeneous roughening of aluminium surfaces is carried out by A.C. electrograining in dilute acids, to produce uniformly pitted and convoluted surfaces. The morphology of A.C. electrograined aluminium surfaces is affected by electrolyte and graining conditions. By comparison of morphologies developed during treatment in hydrochloric and nitric acid, it is proved that the morphological building elements and their ordering are fundamentally different, leading to different final morphologies. The basic elements building up the morphology of surfaces treated in nitric and hydrochloric solutions are respectively a small flat walled hemispherical pit and a fine cubic pit. The effective diameter of the building elements increases, with increasing current density and decreasing graining frequencies. The susceptibility for pitting is higher in chloride solutions: pits are initiated at much lower potentials and at much higher rates; in addition the initiation of pits occurs much faster.     

Preparation of anodic films on 2024 aluminum alloy in boric acid-containing mixed electrolyte

The anodizing oxidation process on 2024 aluminum alloy was researched in the mixed electrolyte with the composition of 30 g/L boric acid, 2 g/L sulfosalicylic acid and 8 g/L phosphate. The results reveal that the pre-treatment and the composition of the mixed electrolyte have influence on the properties of the films and the anodizing oxidation process. Under the condition of controlled potential, the anodizing oxidation current-time response curve displays “saddle” shape. First, the current density reaches a peak value of 8-20 A/dm^2 and then decreases rapidly, finally maintains at 1-2 A/dm^2. The film prepared in the mixed electrolyte is of porous-type with 20 nm in pore size and 500 μm^-2 in porosity. Compared with the conventional anodic film obtained in sulfuric acid, the pore wall of the porous layer prepared in this work is not continuous, which seems to be deposited by small spherical grains. This porous structure of the anodic film may result from the characteristics of the mixed electrolyte and the special anodizing oxidation process. The surface analysis displays that the anodic film is amorphous and composed of O, Al, C, P, S, Si and no copper element is detected.     

Processing and properties of ultrafine-grain aluminium alloy 6111 sheet

The equal channel angular processing (ECAP) technique has been applied to an automotive aluminium alloy sheet (A6111). The technique utilizes a machine that was specially designed for this purpose at Monash University. It was determined that ECAP is able to refine the grain size of the sheet, diminish the detrimental as-rolled texture components in the sheet and retain an acceptable level of bi-axial ductility such as is required during the automotive forming process. Experiments were carried out on annealed, as-received sheets that were subjected to either one or two passes through the ECAP machine. For the second ECAP pass, the sheet could be processed in the same orientation as the first pass (route A) or it could be rotated 180° about the direction of feeding (route C). It was determined that route A produced marginally improved properties compared to sheet processed via route C, and that due to the frictional heating generated during the second pass, a significant amount of recovery occurred in the sheet such that an improved combination of texture and formability resulted after two passes compared to the same sheet exposed to only a single pass.     

毛细管铝封无搭边级进冲挤技术

将挤孔——切连皮——落料——空心件正挤压4种工序巧妙地复合在一套模具上，而且模具结构并不复杂，成功地在400kN冲床上实施了该工艺，使空心毛细管铝封片级进挤压工艺生产率达到每分钟60件，大幅度提高了生产效率。本还在落料工序中采用无搭边新技术，一改冲裁落料中有搭边的常规模式，减少了搭边损耗，大大提高了铝板材的利用率。     

高精深冲用铝合金薄板的开发

论述了各种工艺因素,诸如化学成分,均热制度,热轧及热精轧温度,冷轧变形量,中间退火温度等对罐板用铝合金板的性能,特别是深冲性能的影响。通过试验与分析得出应采取的最佳工艺方案与工艺路线。同时提出了为完善罐板国产化需配套建立先进的辅助生产线的建议。     

485-O铝合金双金属复合板材的研制

研究退火温度对485铝合金双金属复合板组织和性能的影响,制定出合理的工艺制度,生产出满足市场要求的产品。     

Analysis of herring-bone mechanism in sheet rolling

Nowadays, sheet rolling of stainless steel or aluminium has been performed actively. In the sheet rolling, a surface defect called herring-bone, which is a surface pattern like bones of herring, sometimes occurs. On the other hand, a surface defect called reduction-mark, which is many stripes, occasionally happens in the sheet rolling of copper. Since the cause of the surface defects has not been clarified, experimental and theoretical researches are required. First, experiments of cold rolling have been performed. Distances between a line of the herring-bone and that of the neighbouring line have been measured. Moreover, the lengths of projected material-roll contact are are calculated by the slab method. We have found that the distances agree well with the lengths. Secondly, we have proposed a new model of lubrication failure, and have performed analyses of rolling by the slab method based on the model. We assume that the lubrication failure occurs when the average thickness of the lubricating oil becomes smaller than a certain value. The value of frictional coefficient between the material and the roll is assumed to be extremely large when the lubrication failure occurs, whereas the value is assumed to be ordinary when the lubrication failure does not occur. The analytical results show that the lubrication failure occurs periodically toward the rolling direction, and that the period is equal to the length of the projected contact are. Finally, the mechanisms of the herring-bone and the reduction-mark in sheet rolling are clarified by the experiments and the analyses.     

铝合金板成形中摩擦与润滑的研究进展

概述了铝合金板成形过程中的摩擦机理、摩擦模型和润滑的发展现状.全面分析了铝合金板成形的影响因素,阐述了润滑剂的作用机理,展望了其发展趋势,提出铝合金成形应走环保型"绿色"润滑之路.     

Optimization of anodic layer properties on aluminium in mixed oxalic/sulphuric acid bath using statistical experimental methods

The properties of oxide layer obtained on aluminium in mixed electrolytes of oxalic acid-sulphuric acid are optimized using experimental design. For this purpose, a four variables Doehlert design (bath temperature, anodic current density, sulphuric acid and oxalic acid concentrations), was achieved. In order to maximize the growth rate and the microhardness of the anodic oxide layer and to minimize in the same time their chemical and abrasion resistances, a multicriteria optimization using desirability function was conducted. Dissolution rate of the oxide in phospho-chromic acid solution (ASTM B 680-80) was used to express its chemical resistance.Under the determined optimal anodizing conditions (C_ox = 12.6 g L^− 1, 10 °C, 2.6 A dm^− 2, C_sul = 183.6 g L^− 1), the estimated response values were 0.73 μm min^− 1, 4.38 g m^− 2 min^− 1, 481 Hv and 53.3 g m^− 2 for growth rate, dissolution rate, microhardness and weight loss after abrasion respectively. The higher abrasion and chemical resistances of the optimum anodic layer can be correlated with its morphology revealed by AFM and SEM observations.     

变压边力条件下铝合金板的成形窗口

在由塑性成形理论和能量法分别建立的临界破裂和临界起皱压边力模型基础上,构建了变压边力情况下汽车用铝合金板的成形窗口,并分析了拉深比、材料参数和模具参数对成形窗口的影响规律.对比实验表明:在整个有效压边力范围内,数学模型构建的成形窗口能够与实验相吻合,且铝合金6111-T4和5052-O的成形窗口明显小于钢板st14的.而影响因素分析显示:随着拉深比降低、厚向异性系数(r)增加和凹模圆角半径(Rdp)增大,成形窗口明显扩大;n值增加,成形窗口虽然有所扩大,但是效果并不明显.     

CSP冷轧薄板退火过程再结晶机理的研究

采用EBSD分析方法,对CSP试验钢冷轧板退火过程中组织转变和再结晶织构的演变进行分析。结果表明,试验用钢的再结晶过程属定向形核,冷轧基体织构主要是成条状的{111}<110>、{111}<112>和{001}<110>取向。新的再结晶晶粒主要是{111}<112>和{111}<110>取向,且两种取向相互生成。在再结晶温度区间有利于形成{111}<110>和{111}<112>取向,在晶粒长大阶段会生成大量的对深冲性能无明显影响的{112}<110>取向转变。因此,控制再结晶温度区间内形成的{111}取向稳定存在而不发生转变,将有利于提高材料的深冲性能。     

Anodising of 2024-T3 aluminium alloy in electrolyte of sulphuric– boric–phosphoric mixed acid containing cerium salt as corrosion inhibitor

The effect of cerium salt as an inhibitor in anodising of the 2024-T3 aluminium alloy was studied. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy was used to study the surface composition of the alloy before and after surface preparation. A mixed electrolyte of 10% sulphuric acid, 5% boric acid and 2% phosphoric acid containing 0.1 mol/L cerium sulphate salt was used as the anodising electrolyte. Sealing treatment was also done in boiling water and molten stearic acid. Electrochemical impedance spectroscopy and salt spray techniques were performed in order to investigate the corrosion behaviour and durability of the oxide films, respectively. It was concluded that the presence of cerium ions in anodising electrolyte resulted in the increase in homogeneity, the rate of oxide film growth and also the thickness of the oxide layer, owing to the high oxidising power of cerium ion.     

轧制0.005 mm铝箔用铸轧坯料的工艺研究

铸轧坯料的质量是生产出合格0．005-厚铝箔的关键因素。通过从炉底周期性通入高纯N2,精确控制合金成分,用立式铸轧机生产铸轧卷,控制铸轧坯料板形等一系列工艺措施,不断提高铸轧坯料的质量,最终生产出满足轧制0．005mm铝箔要求的合格铸轧坯料。     

夹层钢板冲压的成形机理与缺陷分析

介绍了夹层钢板的材料结构、夹层钢板的冲压成形性及在成形过程中容易产生的缺陷,总结了影响夹层钢板成形性能的因素。介绍了夹层钢板在汽车行业中的应用情况及国内外的研究现状,并指出了当前车用夹层钢板研究的热点难点,对夹层钢板在此行业中应用发展做了展望。     

用KH计算法模拟铝板带冷轧压下规程

分析了冷轧铝板带压下规程的特点,提供了快捷模拟大厂现行冷轧压下规程的步骤,为进一步创新和优化冷轧压下规程创造条件,为工厂节能和增产创造条件。     

In situ temperature measurement on the metal/oxide/electrolyte interface during the anodizing of aluminum

The temperature development during anodizing processes plays a key role in the case of industrial hard anodizing processes. Commonly, only the bath temperature is controlled; although it is well known that the bath temperature can significantly deviate from the temperature across the interface metal/oxide/electrolyte no investigation is known which shows the temperature deviation in this area. The authors have built a special experimental setup which allows a local temperature measurement across the interface. The results show the possibility of local resolved temperature measurements and the calculation of the heat flow into the metal and the anodizing bath. Based on this knowledge a target control of the current‐voltage‐regime avoids the formation of thermally caused cracks in hard anodized layers.     

Investigation of material deformation mechanism in double side incremental sheet forming

Double side incremental forming (DSIF) is an emerging technology in incremental sheet forming (ISF) in recent years. By employing two forming tools at each side of the sheet, the DSIF process can provide additional process flexibility, comparing to the conventional single point incremental forming (SPIF) process, therefore to produce complex geometries without the need of using a backing plate or supporting die. Although this process has been proposed for years, there is only limited research on this process and there are still many unanswered open questions about this process. Using a newly developed ISF machine, the DSIF process is investigated in this work. Focusing on the fundamental aspects of material deformation and fracture mechanism, this paper aims to improve the understanding of the DSIF process. Two key process parameters considered in this study include the supporting force and relative position between master and slave tools. The material deformation, the final thickness distribution as well as the formability under varying conditions of these two process variables are investigated. To obtain a better understanding from the experimental results, an analytical model has been developed to evaluate the stress state in the deformation zone. Using the developed model, an explicit relationship between the stress state and key process parameters can be established and a drop of stress triaxiality can be observed in the double contact zone, which explains the enhanced formability in the DSIF process. Based on the analytical and experimental investigation, the advancements and challenges of the DSIF process are discussed with a few conclusions drawn for future research.     

化妆品包装壳体和盖用1050铝板材生产工艺研究

研究了冷轧及退火制度对1050深冲铝板材制耳的影响。制定出合理的工艺制度,降低了板材的各向异性,生产出具有较低制耳率的深冲板材,适用于制取化妆品壳体和盖。     

The aluminothermic reduction of boric acid

The effect of metallic aluminium powder on the production of boron carbide–alumina composite was studied. Boric acid, carbon and aluminium powders were mixed in stoichiometric ratio, ball milled and heat treated at temperatures between 1300 and 1650 °C for 1–5 h in the presence of argon flow. Depending on the ratio of boron oxide to carbon, the formation of boron carbide by the carbothermal reduction, was possible at a temperature of around 1500 °C, but with the addition of metallic aluminium to the mixture of boric acid and carbon, the carbide formation temperature was reduced at least 300 °C. At 1300 °C, B₄C was the major phase with alumina in the reaction products. The liquid–solid reaction mechanism, which occurred during the aluminothermic process, had a specific influence on the formation of boron carbide.