MA956高温合金活动模板电解加工小孔技术研究

对采用活动模板电解加工技术在MA956铁基高温合金薄板上加工小孔的工艺方法进行了讨论。研究了电解液温度、加工电压、电源占空比和脉冲频率等参数对小孔加工结果的影响。研究表明:采用10%w.t.NaNO_3电解液,在电解液温度为30℃、加工电压为40 V、电源占空比为30%、电源脉冲频率为400 Hz时,能在MA956高温合金薄板上加工获得锥度小的小孔。     

封闭轮廓图形的电解线切割加工试验研究

采用打孔穿丝一体化的方法,对9Cr18Mo不锈钢进行封闭轮廓图形的微细电解线切割加工,研究脉冲电压、脉冲频率、占空比、电解液浓度对加工精度的影响,并探讨影响微缝截面倒圆大小的因素.结果表明:在电解液质量浓度2 g/L、电压17 V、电源频率1000 kHz、占空比30％、进给速度1.2 μm/s的最优条件下,在510 ...     

2344模具钢的脉冲电化学复合光整加工试验研究

为了对2344模具钢进行快速光整加工,进行了2344模具钢的脉冲电化学复合光整加工试验研究。在构建了脉冲电化学复合加工试验机的基础上,进行了正交工艺试验。分析了脉冲峰值电压、脉冲频率、脉冲占空比和电解液温度对光整加工质量的影响,获得了优化的工艺参数。实验表明,在半个小时内可以将试件的表面粗糙度从Ra1.8μm降到Ra0.12μm。     

基于dsPIC单片机的电火花线切割脉冲电源的研制

针对正在进行研制的专用电火花线切割加工机床,自主研制了一种高频脉冲电源。利用SG3525作半桥专用脉冲发生器,16位高性能单片机控制脉冲的频率和占空比,实现了输出脉冲的频率、电压和占空比连续可调。使用IGBT专用驱动后,当加工出现短路时能立即对驱动信号进行软关断,防止IGBT因过流而损坏,极大地提高了脉冲电源在短路发生时的可靠性。用压频芯片对间隙电压进行V/F转换,提高了间隙电压检测的精度和速度,实现了加工间隙电压检测的智能控制。设计了基于触摸屏控制的人机交互界面,将脉冲电源的控制与运动平台的控制有机地统一起来,操作更方便。     

钛合金叶栅套料电解加工表面质量研究

针对TC4钛合金叶栅套料电解加工易点蚀、表面质量差的问题,开展了直流和脉冲电解加工对比研究,设计了脉冲电解加工正交试验,优化了脉冲电压、频率、占空比和加工速度等参数。试验结果表明:脉冲电解加工能减少钛合金点蚀凹坑,提高表面质量,在22 V电压、80%占空比和1000 Hz频率时,加工叶型表面完整无点蚀,加工效率高。     

多孔金属工具阴极电解加工微坑阵列试验研究

采用多孔金属工具阴极电解加工方法,在磷青铜表面加工微坑阵列以增大超声电机摩擦副接触面的摩擦系数,试验研究了脉冲频率、脉冲占空比、加工电压和有效加工时间对微坑阵列尺寸及加工定域性的影响。结果表明:微坑阵列尺寸及加工定域性随脉冲频率的变化而影响很小;微坑阵列加工定域性及微坑深度随脉冲占空比的增大而减小;微坑阵列尺寸随脉冲电压和有效加工时间增大而增大。在磷青铜表面加工时,高电压、短时间、低占空比、高脉冲频率参数时的加工定域性略高。     

Ti-48Al-2Cr-2Nb脉冲电解加工参数优化及试验研究

钛铝金属间化合物Ti-48Al-2Cr-2Nb(TiAl 4822)是一种优良的轻质、耐高温材料,已在航空发动机叶片领域获得重要应用。电解加工是国内外加工TiAl 4822材料的主要方法,与机械加工相比具有显著的效率和成本优势。针对TiAl 4822脉冲电解加工开展了参数优化研究,以加工电压、工具进给速度、电解液温度、脉冲占空比和脉冲频率等参数设计了正交试验,以加工工件的表面粗糙度和单位时间内材料蚀除体积速率为评价指标,采用层次分析法进行了分析,通过单因素试验对分析结果进行了验证。     

电化学光整加工脉冲电源设计

提出了一种基于加工进程自动设定脉冲频率和宽度曲线的脉冲电源设计方案,能根据加工去除量自动调节输出脉冲参数。加工初期,电源输出大占空比脉冲,显著提高材料去除速率;加工后期,输出小占空比脉冲,能有效改善加工精度和表面质量。应用该电源不仅能提高电化学加工效率,还能提高加工精度和表面质量。     

NaCl-乙二醇溶液微细电解加工Ti6Al4V实验研究

采用NaCl-乙二醇的有机盐溶液作为电解液,其具有的少、无氧环境可避免电解加工过程中钛合金表面产生钝化膜,且能提高钛合金的可加工性。通过实验对比了加工电压、脉冲频率、占空比、主轴转速对加工缝宽的影响,进而得到最优的加工参数,并在厚度为0.7 mm的Ti6Al4V工件上加工出了微细结构。     

大功率脉冲电化学光整加工电源的研制

脉冲电化学光整加工技术是近年来新发展的一种高效的光整加工方法,需要用高频窄脉宽大功率的脉冲电源.该电源的设计采用了单片机AT89s52作为主控部分,通过8254-2可编程定时器/计数器输出频率和占空比可调的脉冲方波,并使用M57962AL来驱动和保护IGBT,实现了把直流电压信号斩波成脉冲电压信号输出.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.