Microstructure,mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.     

Effect of heat treatment on microstructures and properties of a novel Al-Zn-Mg-Cu alloy for oil drilling

In view of the special requirements for strength, heat resistance and corrosion resistance of Al-Zn-Mg-Cu alloy for oil drilling, the Al-6.2 Zn-2.5 Mg-1.6 Cu alloy was prepared by increasing Cu content on basis of Russian Series 1953 alloy. The effect of heat treatment on the microstructures and properties of the alloy was characterized by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM), and investigated by tensile test at room temperature, thermal exposure test and corrosion test. The results show that the strength after T6 aging treatment exhibit a decrease trend as an increase of the solution temperature from465 °C to 480 °C. After the solution treated by the rate of 470 °C/1 h, second phases dissolve into the matrix very well and the strength property reaches optimum. The alloy has better comprehensive properties treated by a solution treatment of 470 °C/1 h and then followed by an aging treatment of 120 °C/24 h + 170 °C/1 h + 120 °C/24 h. Under the aging state, the precipitated phases inside the grains are suitable in size, while on the grain boundary distribute discontinuously and the precipitate-free zone is obvious. Besides, the alloy still maintain high tensile properties. The yield strength, tensile strength and elongation are 650 MPa, 686 MPa,12.0%, respectively. The yield strength retention after heat exposure is 92%. The alloy has good corrosion resistance and the exfoliation corrosion degree. The average corrosion rate in the H_2S and CO_2 environment is 0.0024 mm/a, which is far less than the required 0.12 mm/a. It is insensitive to H_2S and CO_2 environments.     

智能高速罐身电阻焊机数字化控制系统

提出了以国产MCT80 0 0F8运动控制器为核心的智能高速罐身电阻焊机数字化控制系统 ,并介绍了系统的组成、工作原理、硬件接口、电机控制方法以及伺服电机的运动关系数学模型 .新的系统有利于提高罐身电阻焊机的制罐生产速度 ,并具有功能全面、可靠性高、控制精确、开放性好以及成本较低等优点     

烟赤净对烟草赤星病的防效

用 8 %烟赤净对烟草赤星病进行田间药效试验 ,结果表明 ,8%烟赤净水剂 80 0倍液的平均防效为 77.12 % ,防效最高 ;4 0 %菌核净可湿性粉剂 5 0 0倍液平均防效为 6 5 .81% ;农用链霉素 2 0 0万单位的平均防效为5 5 .4 1% ,防效最低。     

NIPA类共聚温敏水凝胶中水的状态和耐热性

用N-异丙基丙烯酰胺（NIPA）与丙烯酸钠（SA）及甲基丙烯酸钠（SMA）共聚合成了两个系列的水凝胶，研究了共聚组成与水凝胶基本性质的关系，并用示差扫描量热法（DSC）和热失重法（TG）研究了此类水凝胶中水的状态和耐热性。     

关于差分式放大器输入电阻的研究

差分式放大器在实际应用方面非常广泛,其理论分析方法的深入研究,对生产实践和教学都有重要的意义。采用电路理论分析、差放理论分析、“虚短”理论分析及实验的方法对差分式放大电路进行了研究。     

高贵心灵的无声抗争——《女勇士》与《红字》两则故事相似性之比较

华裔美国女作家汤婷婷的作品《女勇士》中无名女人的故事与美国19世纪浪漫主义小说家纳塞尼尔·霍桑的代表作《红字》中海斯特·白兰的故事都是有关通奸的故事，虽写于不同的时代，但两个故事有着惊人的相似性。本文从两个故事的发生原因，结果以及两位女主人公对通奸行为的态度三个方面简要分析两种通奸行为，旨在阐明通奸行为是两个女人对自由和爱情的追求以及她们对当时父权社会的反抗。     

椭圆偏振法研究四方氧化锆对Zr-Sn-Nb合金氧化膜耐腐蚀性能的影响

将经过不同热处理的Zr-Sn-Nb合金样品放在350℃、16．8mol／LPa、0．01mol／LLiOH溶液的高压釜中进行腐蚀。用椭圆偏振法研究氧化膜中的四方氧化锆，发现经过580℃／冷轧／500℃处理的样品在腐蚀42天和190天后氧化膜中的四方氧化锆比其它样品的多。四方氧化锆是影响合金耐腐蚀性能的一个主要因素，四方氧化锆的形成有利于提高合金的耐腐蚀性能。     

四平市晨晚练点锻炼者参加体育活动的现状调查与分析

采用文献资料、问卷调查法等对四平市晨晚练点锻炼者的现状进行调查分析,发现问题,提出相应的建议,以期促进我市全民健身计划的具体开展与实施,加速社会的现代化过程.     

软件补偿方法在测温智能仪表中的应用

软件补偿方法具有效果好、精确度高、成本低的优点。介绍了在研制多点巡回检测仪中采用的几种软件补偿方法：前向通道特性补偿使放大器等元件不因外界条件的变化而受到任何影响；引线电阻的补偿可实现引线电阻对系统无任何影响；热电阻、热电偶的非线性度补偿效果明显，节省开销。