Numerical simulation of melt flow and temperature field during DC casting 2024 aluminium alloy under different casting conditions

Casting speed,casting temperature and secondary cooling water flow rate are the main process parameters affecting the DC casting process.These parameters significantly influence the flow and temperature fields during casting,which are crucial for the quality of the ingot and can determine the success or failure of the casting operation.Numerical simulation,with the advantages of low cost,rapid execution,and visualized results,is an important method to study and optimize the DC casting process.In the present work,a simulation model of DC casting 2024 aluminum alloy was established,and the reliability of the model was verified.Then,the influence of casting parameters on flow field and temperature field was studied in detail by numerical simulation method.Results show that with the increase of casting speed,the melt flow becomes faster,the depths of slurry zone and mushy zone increase,and the variation of slurry zone depth is greater than that of mushy zone.With an increase in casting temperature,the melt flow rate increases,the depth of the slurry zone becomes shallower,and the depth of the mushy zone experiences only minor changes.The simulation results further indicate that the increase of the flow rate of the secondary cooling water slightly reduces the depths of both slurry and mushy zone.

Microstructural, wettability, and corrosion behaviour of TiO_(2) thin film sputtered on aluminium

The study investigated the application of radiofrequency(RF)-sputtered TiO2 coatings at various temperatures to enhance the hydrophobicity and corrosion resistance of Al6061 alloy.The research aimed to establish a correlation between the coating process and the resulting surface properties.Surface roughness and wettability were quantified with a surface profilometer and goniometer.Additionally,chemical boiling and salt spray corrosion tests were conducted to evaluate any topographical changes during these procedures.The analysis further involved the use of field-emission scanning electron microscopy(FESEM),energy-dispersive spectroscopy(EDS),and X-ray diffraction(XRD)techniques to characterize the deposited coatings.The findings indicated that the TiO2 coating applied at 500℃exhibited the highest water contact angle and superior corrosion resistance compared to other temperatures.Surface characterization confirmed that this specific TiO_(2) coating at 500℃ effectively delays corrosion due to its hydrophobic behavior,making it durable for industrial applications.

Static and Thermal Analysis of Aluminium (413,390,384 and 332) Piston Using Finite Element Method

The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.

Effectiveness of Sodium Silicate on the Corrosion Protection of AA7075-T6 Aluminium Alloy in Sodium Chloride Solution

The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na2SiO3. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.

激光清洗时氟碳铝粉漆层表面粗糙度的分析及其对激光吸收的影响

激光清洗2024铝合金飞机蒙皮表面漆层过程中,粗糙表面的形成与演化会对漆层与激光的热交互作用及漆层去除机理产生较大的影响.1 064 nm脉冲激光逐层除漆过程中,分析了漆层表面形貌与粗糙程度的变化,研究了粗糙表面的产生机理及其演化规律,并通过建立漆层粗糙表面等效分析模型计算分析了漆层粗糙表面对激光吸收率的影响规律.结果表明,激光除漆过程中不同的去除机理作用后漆层均会出现粗糙表面,且粗糙表面的演化存在一定的规律;逐层除漆时,漆层粗糙表面对激光吸收率有明显增加作用,在激光作用7次后漆层粗糙表面对激光的吸收率增加了32.8%,如果采用固定的初始激光清洗工艺,会因吸收率增大导致铝合金基材产生损伤行为.

单点渐进成形工艺参数对铝合金圆锥台表面粗糙度的影响

表面粗糙度是影响渐进成形零件质量的关键因素之一,为了探究工艺参数对零件表面粗糙度的影响,采用单点渐进成形技术对5052铝合金板料进行成形实验,研究工艺参数轴向进给量、主轴转速、进给速度对圆锥台表面质量的影响,并使用粗糙度仪测量外表面粗糙度R_(a)值。实验结果表明:降低轴向进给量可以改善零件表面质量;随着主轴转速增大,零件粗糙度R_(a)呈先减小后增大趋势;进给速度对粗糙度R_(a)影响较小,随着进给速度增大,粗糙度R_(a)呈先减小后增大趋势,受零件尺寸限制,进给速度超过2817 mm·min^(-1)时,内表面“鱼鳞纹”和粗糙度R_(a)几乎没有变化。

焊接方法对铝合金焊接接头微弧氧化色差的影响

目的分析铝合金焊接接头微弧氧化过程中色差产生的原因。方法采用单激光和激光-MIG复合焊2种焊接方法焊接2A12铝合金,利用RGB值定性描述不同焊接试样的色差差异大小,采用金相、SEM和微区XRD观察2A12铝合金单激光和激光-MIG复合焊接头微弧氧化前后的组织、微观形貌和表面物相组成。结果经微弧氧化处理后,2A12铝合单激光焊焊件的焊缝和母材之间无明显色差,2A12铝合金激光-MIG复合焊焊件的焊缝和母材之间存在明显色差,结合金相组织、表面和截面的SEM形貌以及表面EDS和XRD测试分析结果可知,成分和表面熔融物颗粒的大小不同是铝合金焊接接头微弧氧化色差形成的主要原因,焊接接头的组织对铝合金焊接接头微弧氧化色差的产生没有影响。结论单激光焊接接头微弧氧化后的氧化色差较激光-MIG复合焊接头的小;铝合金(2A12)焊接接头产生氧化色差主要是因为焊接接头的成分和表面熔融物颗粒大小不同,而组织对色差无影响。

基于COMSOL的7075铝合金微弧氧化时间及正向电压对氧化膜层的影响

研究了微弧氧化时间及正向电压对7075铝合金膜层厚度以及生长趋势的影响。以7075铝合金为研究对象,在多物理场仿真软件COMSOL Mutiphysics的帮助下建立铝合金成膜过程中的物理模型,基于有限元的方法求解出了微弧氧化成膜过程中的膜层厚度变化。仿真得到特定时间或者特定电压下的膜层厚度分布图,根据仿真结果绘制了电压-膜层厚度曲线、时间-膜层厚度曲线。由仿真结果可以看出:当正向电压分别为350、400、450 V时,膜层的最大厚度分别为38.804、50.150、61.496μm;当微弧氧化时间分别为15、25、35、45 min时,膜层的最大厚度分别为25.075、41.792、58.508、75.225μm,且膜层厚度均呈现由中间向两侧逐渐减小的现象。根据仿真结果可以得出以下结论:随着正向电压的升高,膜层厚度增大;随着氧化时间的增加,膜层的厚度也增加。在膜层厚度分布上,越靠近阴极的位置膜层越厚,远离阴极的位置膜层比较薄,且不同参数下膜层的最厚点与最薄点出现的位置不变。

药用辅料硅酸镁铝(IB型)黏度测定方法探讨

目的:确定硅酸镁铝(IB型)登记备案标准中黏度测定方法是否可行。方法:采用棒状高速搅拌器及旋转黏度计考察硅酸镁铝(IB型)黏度,采用破壁机及旋转黏度计考察硅酸镁铝(IB型)黏度。结果:采用棒状高速搅拌器及旋转黏度计考察硅酸镁铝(IB型)黏度时,样品均不符合规定,采用破壁机及旋转黏度计考察硅酸镁铝(IB型)黏度时,样品均符合规定。结论:硅酸镁铝(IB型)为触变性非牛顿流体,其黏度测定结果受高速搅拌器类型影响较大,建议药用辅料登记备案标准中明确使用的高速搅拌器类型,细化前处理方法。

不同温度下铝合金摩擦机制的分子动力学研究

铝合金成形过程中与模具接触会发生摩擦磨损,直接影响零件成形质量和模具使用寿命,且铝合金摩擦性能受温度影响。基于分子动力学方法,针对原子尺度研究了铝合金摩擦机制的温度相关性,分析不同温度下铝合金摩擦过程中力学性能、摩擦系数、表面形貌和内部结构变化。结果表明:铝合金抗变形能力随着温度降低而增强,600K下的摩擦系数比83K低7%;随着温度升高,铝合金塑性变形程度增大,形变原子数量增多;在铝合金内部,因变形产生的缺陷原子数量和位错运动范围与温度呈正相关趋势。因此,高温有利于降低铝合金成形摩擦,而低温可以提高铝合金抗变形能力,有利于减少磨损,提高零件成形质量。

河南偃龙地区晚石炭世风化作用与铝土矿成矿过程

通过对偃龙地区铝土矿成矿的古地理环境特征、含矿岩系的岩相学特征、岩石矿物特征、成矿元素富集特征的研究,分析了晚石炭世本溪组铝土矿风化成矿作用的三个阶段脱硅富铝的动态变化过程,进而探讨了本区晚石炭世风化作用条件下的铝土矿成矿过程。研究结果认为,在风化作用为主的铝土矿成矿过程中,含矿母岩首先生成黏土矿物,然后当岩石中Al_(2)O_(3)含量接近35%时,开始生成以三水铝石为主的最初铝土矿,最后铝土矿在盖层覆盖下,在一定的温度压力条件下三水铝石转化为一水硬铝石,并最终形成“煤-黏土-铝土-铁质黏土”这种本溪组铝土矿系的典型结构。

农机轻量化所用铝合金精炼装置关键密封结构研究

阐述了农机轻量化的现状和必要性,对石墨材料的组织、特性和工艺进行了分析研究,并设计了一种铝合金精炼用石墨转子与石墨转轴密封结构。实验结果表明:该结构利用热装技术在石墨转子与石墨转轴的密封接触面形成夹持力,使两者在密封部位充分接触,微填料形貌符合预期,达到从宏观上阻塞气体熔剂目的,从而大大提升了铝液精炼装置的除氢效率,提高了农机轻量化所用铝合金的品质。

X射线荧光光谱法测定锌合金中铜和铝的含量

建立了一种通过X射线荧光光谱法测定锌合金中铜、铝含量的方法,并利用整套锌合金标准样品建立了标准曲线,优化了仪器条件,采用经验系数法对基体效应进行了校正。对参与曲线建立的标准品进行测定,测定值的相对标准偏差为铜0.4%、铝0.04%;对未参与曲线建立的标准品进行7次测定,测定结果的平均值与认定值的差值绝对值铝为0%、铜为0.03%,均小于现行国家标准方法的重复性限。

降低6061铝合金宽幅加筋板型材平面度的工艺研究

研究了高温在线整形工装和仿形拉伸工装对6061铝合金挤压宽幅加筋板型材平面度的影响。结果表明,通过高温在线整形和采用仿形拉伸垫块进行拉伸矫直,可有效降低6061铝合金挤压宽幅加筋板型材的平面度。相比之下,高温在线整形对降低宽幅加筋板型材平面度的的效果比采用仿形拉伸垫块更明显。高温在线整形是利用铝合金在高温状态下硬度低、易矫直的特点,通过施加外力的方式对高温状态下的型材进行在线整形,使宽幅加筋板型材获得良好的平面度,同时配合使用仿形拉伸垫块进行拉伸矫直,生产的6061铝合金挤压宽幅加筋板型材可满足客户对平面度的要求。

激光冲击强化7075铝合金数值模拟与试验分析

针对激光冲击强化7075铝合金的问题,利用有限元技术和试验方法进行研究。首先利用光学显微镜、电子背散射衍射、显微硬度试验分析激光冲击前后试样上表面和横截面上微观组织和力学性能。其次采用有限元软件对7075铝合金进行数值模拟,得到应力变化云图和残余应力云图。试验结果表明,激光冲击细化表面和横截面晶粒组织,表面和横截面上再结晶晶粒占比分别从激光冲击前6.5%和8.3%提升到33.0%和80.1%;激光冲击后表面平均显微硬度提升幅度超过15%;随着深度增加,横截面上显微硬度提升幅度逐渐衰减。数值模拟结果表明,激光冲击过程中应力从447 MPa提升到581 MPa,在稳定时降到550 MPa;激光冲击提高了表面残余应力,而横截面上应力随着厚度增加而衰减。

Microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy by micro-arc oxidation

The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.

Shear deformation and plate shape control of hot-rolled aluminium alloy thick plate prepared by asymmetric rolling process

Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.

Effect of additives on properties of aluminium titanate ceramics

The influence of some additives on bulk density,phase composition,mechanical strength and thermal shock resistance of aluminium titanate （AT） ceramics was investigated.AT ceramics with different additives of MgO,SiO2 and Fe2O3 were prepared by reaction sintering.Properties of AT ceramics were tested by using Archimedes,three-point bending and thermal cycling tests.It was found that additives of MgO,SiO2 and Fe2O3 or their compound additives are favorable to reduce the porosities of AT,enhance mechanical strength and thermal shock resistance.The role of additives can be rationalized in terms of promotion of sintering process,formation of new phases and influence on lattice constant c of AT ceramics.

Visualization and simulation of plastic material flow in friction stir welding of 2024 aluminium alloy plates

Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visualized material flow patterns, a three-dimensional model was developed to conduct the numerical simulation of the temperature profile and plastic material flow in friction stir welding. The calculated velocity contour of plastic flow in close proximity of the tool is generally consistent with the visualized results. As the tool rotation speed increases at a constant tool travel speed, the material flow near the pin gets stronger. The predicted shape and size of the weld nugget zone match with the experimentally measured ones.

Effect of pre-stretching on microstructure of aged 2524 aluminium alloy

The effects of pre-stretching following solution treatment on the hardness and microstructures of aged 2524 aluminium alloy at 170 ℃ were studied.Ageing hardness values under different pre-stretching conditions were measured,and the corresponding microstructures were characterized by transmission electron microscopy（TEM）.The results show that compared with unstretched samples,the peak hardness is increased and the time to reach the peak hardness is reduced with the increase of pre-strain;the number density of S（Al2CuMg） phases is increased and the length is shortened in pre-stretched alloy.Additionally,the number density of GPB zones is decreased with the increase of pre-strain in peak-aged samples.When the pre-strain is up to 5%,S phases play the predominant contribution to the peak hardness.Fine and uniformly distributed S phases lead to a higher hardness than GPB zones together with S phases existing in conventionally aged 2524 alloy.