复合工艺对半固态A356铝合金浆料组织的影响

用低过热度浇注和弱行波电磁搅拌工艺制备A356铝合金半固态浆料,研究了浇注温度和搅拌功率等复合工艺参数对A356铝合金的半固态浆料的影响i结果表明,这个复合工艺促使初生α-Al几乎在整个熔体区域形核,增加了初生α-Al同时形核的位置和数量,在合金凝固的初期形成足够多的晶核,从而在合金熔体中形成球形或近球形的组织.在浇注温度和浇注功率分别为630℃和1.2 kW条件下可以制备出球状初生α-Al晶粒的A356铝合金半固态浆料.与单纯低过热度浇注的A356铝合金试样相比,在弱行波电磁搅拌条件下,适当提高浇注温度也可获得理想的球状A356铝合金浆料,同时可简化浇注工艺.     

旋转直管浇注法制备A356铝合金半固态浆料

采用旋转直管浇注法制备A356铝合金半固态浆料,在不同浇注温度和转速下进行了系列试验,并与直管法进行了对比分析。结果表明,在不同转速条件下,浇注温度越低,得到的浆料凝固组织晶粒尺寸就越小,颗粒球化程度越高。与直管法相比,同一工艺参数下,旋转直管法制备的坯料的晶粒更为细小和圆整,并且随着旋转速度的增加,可得到理想浆料组织的浇铸温度区间也随之增大。本实验条件下,当转速为300r/mim时,浇注温度为670℃也能得到较理想的半固态凝固组织。     

电磁搅拌频率对半固态A356初生α相的影响

利用低过热度浇注和电磁搅拌技术制备半固态A356铝合金浆料。采用变频技术控制电磁搅拌装置,探讨了电磁搅拌频率对半固态初生α相形貌的影响;通过数值模拟获得了磁感应强度较强的电磁搅拌频率。研究结果表明,在半固态A356合金浆料的制备过程中,电磁搅拌频率对半固态初生相的形貌影响很大,通过实验研究获得了制备半固态A356铝合金浆料的合适工艺参数,即在浇注温度620℃、保温温度590℃、保温时间10min、搅拌时间15s的条件下,搅拌频率为30Hz的晶粒细化效果最佳,其平均形状因子为0.80,平均等级圆直径为76.1μm。     

A356合金近液相线半固态铸造非枝晶组织与模锻成形性能

采用近液相线铸造技术制备出具有等轴晶粒的半固态A356合金坯料,合适的铸造工艺为铸造温度615℃、铸造速度160mm/min、液面深度220mm、冷却水流量0.1m3/min;在电阻炉加热的条件下,半固态A356合金坯料的重熔加热温度场均匀,合适的加热制度为保温温度585℃,保温时间10min。在模具温度为300℃~500℃条件下,触变模锻成形了汽车轮毂件,经T6热处理后的抗拉强度为215.65MPa,延伸率为14.45%,硬度为78.66HV,该研究结果对半固态加工技术在汽车零部件生产领域的应用有积极意义。     

液相线模锻法制备ZK60-RE镁合金半固态组织演变

给出了液相线模锻法制备ZK60-RE镁合金半固态坯料的实验方法和工艺参数,并研究了该方法制备的ZK60-RE镁合金在半固态等温热处理过程中的微观组织演变.结果表明:利用液相线模锻法可以制备半固态ZK60-RE镁合金坯料,半固态ZK60-RE镁合金坯料在保温时间较短的半固态等温热处理过程中能形成晶粒细小、晶粒粗化速度较为缓慢的球晶组织,晶粒在600℃保温15 min、610℃保温3 min和618℃保温0 min时分别达到最小,最小尺寸分别为35、45、30 μm,能够达到半固态加工实际化生产的较高要求.晶粒在不同的温度下随着保温时间的延长,晶粒的圆整度均逐渐变小,球晶化越来越好.     

触变模锻成形工艺对镁合金成形件力学性能的影响

采用半固态等温热处理法、近液相线模锻法和等通道角挤压法制备AZ91D-Y镁合金半固态坯料。分别将3种状态的坯料加热到半固态温度区间进行二次重熔后,进行了触变模锻成形。结果表明,在半固态温度为560℃,模锻压力为200MPa的条件下,半固态等温热处理法、近液相线模锻法和等通道角挤压法制备坯料分别保温30,20,15min后触变模锻获得最佳力学性能;随着坯料加热温度的升高,触变模锻成形件力学性能呈现先上升后下降的趋势;增加成形压力有利于触变模锻成形件力学性能的提高;在相同成形条件下,等通道角挤压法制备坯料触变模锻后的力学性能最好,近液相线模锻法次之,半固态等温热处理法较差。     

电磁搅拌与浇注温度对半固态A356铝合金中微量稀土细化初生相的影响

在不同浇注温度和电磁搅拌制度下制备了A356铝合金半固态浆料,研究了微量稀土下浇注温度、电磁搅拌频率和时间对半固态A356铝合金初生相形貌及力学性能的影响。结果表明,通过优化半固态制浆工艺条件减少稀土的加入量是可行的,实验表明稀土微量化的合适工艺方案是:浇注温度为630℃,电磁搅拌频率为30Hz,搅拌时间为8s。此时,加入量为0.3%的稀土La细化效果和常规加入量为0.4%La的低过热度浇注的相当,其力学性能也基本相同。     

用新工艺制备半固态铝合金浆料

用低过热度浇注和弱电磁搅拌工艺制备A356铝合金半固态浆料，研究了浇注温度、搅拌功率和搅拌时间对A356铝合金的半固态浆料的影响．结果表明，用该工艺可以制备出球状初生α—Al晶粒的半固态A356合金浆料．与单纯低过热度浇注的试样相比较，在弱电磁搅拌条件下，适当提高浇注温度亦可获得理想的球状A356合金浆料，也简化了实际浇注工艺的操作．低过热度浇注和弱电磁搅拌，加速了合金液向外传热和减小了其温度梯度，扩大了同时凝固的区域，细化了初生α—Al晶粒，造成的强迫流动，扩大了合金熔体的温度扰动和局部温度起伏，促使初生α—Al二次臂的熔断和球状初生α—Al晶粒的形成．     

半固态A356铝合金浆料的充填行为及组织分布

采用流变压铸方法研究了低过热度浇注和弱电磁搅拌制备的半固态A356铝合金浆料的充填行为和组织分布,结果表明：采用该技术制备的半固态A356铝合金浆料,其组织形态优良,经过感应均热后,浆料内部的温度场分布均匀,初生α—Al晶粒更圆整．半固态A356铝合金的浆料温度、压射比压和冲头速度对浆料的充填行为有较大的影响．较高的浆料温度、压射比压和冲头速度都有利于半固态铝合金浆料的充填．在本文的实验条件下,合适的浆料温度为585-595℃,压射比压为15-25MPa,冲头速度为0．072-0．12m／s．得到的流变压铸件的组织分布均匀,无明显的固液相偏析．     

A356铝合金液相线铸造形核规律

研究了液相线铸造A356铝合金在不同保温温度、不同保温时间下的组织形成规律。电子显微镜及图象分析仪分析表明，由于过冷和扩散的共同影响，A356铝合金液相线铸造最佳保温温度605℃；在60min时间内，晶核数目随保温时间的延长而增加，且分布愈加均匀。     

A Development of A Computer aided Ferrographic System

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A Noise-Tolerant Hybrid Model of A Global and A Local Learning Module

Proposed is GLLL2, a hybrid architecture of a global and a local learning module, which learns default and exceptional knowledge respectively from noisy examples. The global learning module, which is a feedforward neural network, captures global trends gradually, while the local learning module stores local exceptions quickly. The latter module distinguishes noise from exceptions, and learns only exceptions, which makes GLLL2 noise-tolerant. The results of experiments show the process in which training examples are formed into default and exceptional knowledge, and demonstrate that the predictive accuracy, the space efficiency, and the training efficiency of GLLL2 is higher than those of each individual module.

     

新型表面可修饰性有机硅密封材料的制备及应用

制备了一种单组分室温硫化表面可修饰性有机硅密封材料。在通用的酮肟型有机硅密封材料组分中,添加自制的含有氰基、仲胺基的硅烷改性剂,可明显改善油溶性醇酸漆和聚氨酯漆对有机硅密封材料的可涂覆性及储存稳定性。添加甲基丙烯酰丙基三甲氧基硅烷,同时在水溶性丙烯酸乳胶漆中添加适量的硅丙乳胶,可显著改善水性丙烯酸乳胶漆对有机硅密封材料的表面可修饰性。表面可修饰性有机硅密封材料可用作普通有机硅密封胶的底涂。     

Allocating A Replenishment Order Among A Family of Items

Inventory control models which provide coordinated control (or joint replenishment) of families of items are very useful in practice. An important component of these models is the algorithm for allocating a total reorder quantity among the items in the family. In this paper the allocation algorithm from a new class of coordinated control models is discussed. Inventory position is modelled as a diffusion process, and both continuous review and periodic review situations are considered. This new class of coordinated control models has been shown to outperform existing models (IBM's IMPACT Inventory Control Package).     

D／A转换器的模型化测试策略

本文提出了模型化测量D/A转换器非线性误差的方法,讨论了建模技术和选择优化试验点的方法。利用这些工具,可以从一组充分、必要的测量数据,准确估计出在所有码态时转换器的非线性误差、位误差和重叠误差。     

Oscillating Cup Viscosity Measurements of Aluminum Alloys: A201, A319 and A356

An oscillating cup viscometer was developed to measure the absolute viscosities of molten metals. Previous experiments established the capability of the apparatus to characterize the viscosities of molten nickel-based superalloys. However, modifications to the instrument and its theoretical analysis were required for reliable measurements on molten aluminum alloys, presumably due to their lower densities and lower viscosities. The theoretical literature for the fluid flow inside an oscillating cup is reviewed, and a working equation without any correction factor is developed for the improved viscometer. Some design parameters of the viscometer that directly affect the accuracy of viscosity estimation by using the working equation are discussed. A special vertical furnace was adopted to uniformly heat a longer cylindrical sample (10 mm inner diameter and 120 mm length) with a temperature difference of less than 2°C over the sample length. The measuring procedure was also improved to get more accurate motion parameters. It is estimated that the working equation and improved instrument provide an uncertainty of less than 4%. In addition, applications and experimental data are presented for pure aluminum and three aluminum alloys: A201, A319, and A356.     

A model of flocculation

The phenomenon of flocculation in liquid suspensions has a variety of applications, including mineral processing, treatment of industrial effluents, and municipal sewage sludge purification. Obtaining metals from ores would not be possible without the slurry processing route. Flocculants play here a double role: limiting environmental contamination and also slowing down depletion of raw materials — including potable, industrial and agricultural water. Development of better flocculants requires improved understanding of the mechanism of their action. We propose a model of flocculation based on the assumption that effective flocculants pervade large volumes of liquids in the suspensions. Since many flocculants are polymers, good flocculants according to the model should have large radii of gyration R_G. We therefore assume a connection between R_G and settling velocities y of particles out of suspension. Four different types of aqueous suspensions are studied, containing in turn silica, coal, Mn ore and Fe ore. A unique relationship is demonstrated between R_G and y for several polymeric flocculants in each type of slurry. For each suspension type the corresponding equation has the form y = aR_G^b, where the two parameters characterize the suspended particles and the liquid medium. While polysaccharides from natural sources are used as flocculants, we show how their cationization enhances the flocculation efficiency in all media we have studied. Large effects are achieved for the flocculating agent concentrations in the range of 6-9 ppm.     

一句话、一个人和一本书影响了我

Q=你应该从大二就开始了兼职设计工作。当初什么样的机会让你和设计有了实践上的接轨？当时的你最希望从实践中获得的东西是什么？后来到底得到了怎样的收获？A——我初次参与设计兼职工作是在大二时的暑假。一个偶然的机会．有朋友介绍我与其他两位同学与几家展览公司进行一些接触。当时是上海会展行业初步呈现规模、开始发展壮大的时期．有些展示公司由于业务繁忙，需要一些勤奋肯干的兼职学生参与设计，于是就有机会开始了最初的实践。后来也逐渐接触了另几家会展公司,参与了更多的展示设计工作，可以说基本上在大学的设计实践绎聆伞部来自干展示展览设计．     

天山风景线

“你们那里的时间,比我们这里晚两小时。”这是内地朋友常说的一句放,穿梭于这种时差之间,意识和身体总也在游离。常常产生的不确定使表达和判断无从标准。