AZ31镁合金轧制板材退火后的组织与力学性能

采用单向轧制和交叉轧制工艺分别进行了AZ31镁合金板材轧制实验,分析了轧制板材经退火处理后的组织与力学性能。结果表明:采用单向轧制工艺,当板材最终变形量相等时,经退火处理后的板材大压下量比小压下量得到的微观组织更为细小;交叉轧制得到轧制板材可以缓解镁合金轧制板材在室温下的各向异性,其微观组织较单向轧制均匀,具有更好的冲压成形性能;交叉轧制和单向轧制两种工艺得到的板材微观组织细化效果相似。     

轮廓运动的交叉耦合模糊自整定控制

该文对CCC（Cross-Couple Control）交叉耦合控制算法进行了详细地讨论.针对通常PID-CCC控制器参数的整定困难问题,在轮廓误差传递函数（CETF）的基础上提出采用在线模糊CCC控制器参数自整定方法.该控制器对被控对象模型有较好的鲁棒性,仿真结果证明算法是可行和有效的.     

超大孔径聚晶金刚石拉丝模具单向走丝电火花线切割加工工艺研究

基于试验研究,创新性地提出了采用单向走丝电火花线切割机床对超大孔径聚晶金刚石拉丝模具的孔形进行粗加工。以金刚石粒度为25μm的直径22 mm、厚度20 mm的超大孔径聚晶金刚石拉丝模具为例,进行单向走丝电火花线切割加工定径区、压缩区和安全角的工艺研究,得出了加工工艺曲线,确定了最优加工工艺参数,提高了粗加工效率,确保了良好的孔形精度。结果表明:选择脉冲宽度4μs、脉冲间隔40μs、峰值电流15 A、走丝速度10 m/min时,可获得较满意的加工效果。     

单向玄武岩纤维布的可压缩性研究

本文采用纤维压缩模型对玄武岩单向布在压实过程阶段的可压缩性进行了研究.结果发现,玄武岩单向布的压缩过程符合Gutowski方程,并且与织物铺层厚度无关.并在此基础上通过对试验数据的拟合,得到了描述玄武岩单向布压实过程中纤维体积含量变化的具体方程.     

下引式连续定向凝固薄壁铜管中具有温度梯度的结晶器对固液界面位置影响的数值模拟与分析

根据凝固原理建立了下引式连续定向凝固薄壁铜管过程中具有温度梯度的结晶器下二维稳态温度场的物理、数学模型,并通过数值计算与绝热结晶器、恒温结晶器下工艺参数对固液界面位置的影响进行对比分析,结果表明在保证熔体温度稳定的条件下,使用具有温度梯度的结晶器能够获得相对较宽的适宜工艺参数范围以及较高的极限拉坯速度.     

接触反应钎焊中间层材料的选择原则--接触反应共晶液相产生的方向性

以Al/Cu ,Al/Si接触反应偶为例 ,研究了不同基体与反应材料组合下 ,共晶液相的产生及其铺展行为。结果表明 :Al/Cu ,Al/Si接触反应偶中共晶液相的产生具有明显的方向性—优先在Al侧产生 ,这是扩散偶之间的互扩散系数不等所造成的必然结果。而在接触反应钎焊的中间层材料选择过程中 ,考虑接触反应液相产生的方向性是发挥接触反应钎焊优越性的保障     

Evaluation of atmospheric galvanic aluminum corrosion in electrical transmission towers at different sites in the Valparaíso region,Chile. Wire-on-Bolt Test (CLIMAT)

This study evaluates environmental aggressiveness and atmospheric galvanic corrosivity categories in Chile (Classification of Industrial and Marine ATmospheres test) by installing bolts in electrical transmission towers in the Valparaiso region across four exposure sites: Playa Ancha, San Sebastián, Las Vegas, and San Felipe. Classifications of marine corrosion index (MCI), industrial corrosion index (ICI), and atmospheric corrosion index (ACI) used different galvanic couples: aluminum/steel for MCI, aluminum/copper for ICI, and aluminum/polyethylene for ACI. Corrosion indices varied by season (summer, autumn, winter, and spring), for which couples were exchanged every 3 months. Intraseason variation depended mainly on the meteorochemical variables of the zone, the Cl⁻/SO₂ ratio, and the presence of general and pitting corrosion in the aluminum. The results indicate that, regardless of environmental condition, the aluminum in Al/steel (MCI) and Al/copper (ICI) couples presented a higher corrosion rate than when not forming a galvanic couple (ACI). Moreover, under higher environmental chloride, these differences increase. The Playa Ancha station presented the highest ACI.     

单向走丝电火花线切割电极丝的分类及发展

正确选用单向走丝电火花线切割的电极丝,对高速切割和高精度加工起着至关重要的作用,对提高工艺稳定性和降低加工成本也有重要的影响。通过叙述单向走丝电火花线切割电极丝从紫铜丝到镀锌丝的发展过程,以及电极丝的性能、种类及优缺点等,进一步分析了电极丝的发展趋势,有助于加工时对各类电极丝的正确选用。     

Formation of twinned dendrites during unidirectional solidification of Al-32%Zn alloy

The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn (mass fraction) alloy. The morphology was investigated by optical metallograph and electron back-scattered diffraction technique. Results showed that the macrostructure of the alloy exhibited a typical feathery and fan-like structure while the microstructures were elongated lamellas, which were separated by coherent and incoherent twin boundaries. Both the primary trunk and all lateral arms of twinned dendrites grew along 〈110〉 directions, unlike regular 〈100〉 α(Al) dendrites. The facet growth of crystals at solid/liquid interface was responsible for the origin of twinned dendrites during the weak local convection, and high thermal gradient and medium solidification velocity had significant contribution to the formation of twinned dendrites. The formation mechanism of twinned dendrites which consisted of three multiplication ways of new twin boundaries formation and one way of dendrite evolution in twin plane was shown schematically.     

水热电耦合法制备BaZrO3薄膜

本研究采用水热电耦合方法合成了BaZrO3薄膜。首先通过阴极放电等离子体(HCD-IP)在Si基片上沉积氮化锆(ZrN)薄膜,接着将包覆ZrN的Si基片侵入到水热电耦合装置中,其混合溶液为Ba(CH3COO)2和NaOH,在90℃的温度下工作1～15h。结果表明,在ZrN/Si基片上成功合成了立方BaZrO3薄膜。BaZrO3薄膜在ZrN上的生长速率比在块体Zr上的生长速率快,BaZrO3薄膜展示出纳米层结构,其厚度在15h后可达到2μm。本文讨论了溶液的反应温度和反应时间对薄膜形貌和厚度的影响。