铝熔体精炼处理后确定最佳浇注时间的研究

用英国制造的ＨＹＳＣＡＮ Ⅱ测氢仪, 试验研究了铝合金精炼时的除气和再吸气过程, 并对其机理做了分析, 建立了氢原子运动模型。试验发现, 铝熔体精炼后, 静置一段时间才达到最佳除气效果。静置所需时间和熔体表面状态有关： 精炼后立即扒去表面浮渣, 静置５ ～６ 分钟为最佳; 带渣静置, 一般为１０～１２ 分钟。铝熔体应当在达到最佳除气效果时浇注。     

铝熔体除氢精炼工艺的研究

建立了气泡浮游法除气的数学模型,分析了模型中参数对除气效果的影响,用Hyscan Ⅱ测氢仪现场试验研究了数学模型中的参数对除气效果的影响,比较了氮气和氩气的除气效果。试验发现,氩气的除气效果好于氮气的除气效果,浮游法除气后的最佳静置时间为30min左右,铝熔体的最佳浇注温度为680～685℃。     

旋转喷头法实现铝熔体高效除氢的基本条件

以气体为熔剂的气泡浮游法铝熔体净化技术为研究对象，在熔化环境条件一定和气体熔剂质量符合除氢工艺要求的前提下，从过程动力学角度出发，就铝熔体内部的净化剂气泡去氢和铝熔体表面吸氢两个方面，叙述了旋转喷头法能实现高效除氢净化的基本条件。     

强剪切作用下氩气泡破碎行为及其对7075铝合金除气效果的影响

采用一种新型定子-转子型强剪切装置,通过水模拟实验和铝熔体除气实验相结合的方法研究强剪切作用对铝合金除气过程中氩气泡的影响规律,进而研究其对7075铝合金的除气作用。结果表明:强剪切对氩气泡具有强烈的破碎和分散作用,能够将通入熔体的气泡转变为非常细小的气泡,并均匀分布于熔体之中。这种强剪切作用对7075铝合金具有非常高效的除气作用。在适当的除气条件下,经过1 min除气,合金密度指数D_i由13.20%降低到0.65%,实测铝中氢的含量由2.90μL/g降低到1.10μL/g,这显著优于传统旋转除气方法。还详细研究除气时间以及除气后静置时间对氢含量的影响,并分析强剪切工艺高效除气的机理。     

铝合金熔体真空处理的某些问题

现在在铝合金毛料铸造工艺中已开始采用熔体真空处理法。早些时候的研究者确定,将少量熔于真空下保持15—20分钟,溶解的氢浓度达到平衡值。但是在真空静置炉中工业熔次的除气实践证明,为了达到平衡浓度要求较长的时间。据我们看来,这种状况与大容量熔体的除气特点有关。大家知道,除氢有两条途径。除气过程动力学大致如图1。在达到t＇时刻以前,除氢既靠扩散又有赖于气泡析出。这时氢含量减少,于是熔体内氢的平衡蒸气压也减少,对于一定金属水平h来说,在t＇时氢的平衡蒸气压变成等于反对气泡出现的外界压力。在此水平上氢     

7075铝合金旋转喷吹精炼工艺的研究

采用正交试验的方法,研究了旋转喷吹精炼工艺中的气体流量、转子转速、精炼时间和静置时间4个参数对7075铝合金精炼效果的影响;采用对比试验研究了C2Cl6精炼工艺、旋转喷吹精炼工艺及C2Cl6 旋转喷吹精炼的混合工艺对7075铝合金除气效果的影响.结果表明,转子转速对除气效果的影响最大,气体流量、精炼时间次之,静置时间的影响最小,优选出的最佳方案是转子转速为400 r/min,气体流量为0.4 mL/h,精炼时间为15 min,静置时间为6 min;采用C2Cl6精炼除氢率为34.5%左右,采用旋转喷吹精炼除氢率为70%左右,采用C2Cl6 旋转喷吹精炼的混合工艺除气效果最佳,除氢率为78%左右.各精炼工艺对合金力学性能的影响也不同,C2Cl6 旋转喷吹混合精炼的铝合金试样的抗拉强度、屈服强度和伸长率均最高,旋转喷吹精炼的次之,C2Cl6精炼的最低.     

AZ31镁合金熔体超声净化处理

利用超声处理AZ31镁合金熔体,考察了超声功率及静置时间对净化效果的影响,分析了超声熔体净化的机理。结果表明,超声处理可以加速熔体中夹杂物的凝聚,实现AZ31镁合金熔体的净化。AZ31镁合金熔体超声处理的最佳超声体积功率密度为0.30 W/cm3,适当延长静置时间对净化有利。铸锭中夹杂物越多,电导率越小,电导率可以表征铸锭的净化程度。     

氢还原除鳞后的冷轧带钢退火工艺北大核心CSCD

采用氢还原法去除带钢表面氧化铁皮绿色环保,但氢还原后的带钢表面出现脱碳现象,且内部组织粗化,冷轧及退火后可能遗传给成品带钢。本文对氢还原后的热轧带钢进行了冷轧和退火试验,研究了氢还原除鳞后的冷轧带钢在退火过程中的组织性能演变规律,分析了退火温度和退火时间对带钢组织性能的影响。结果表明：经过氢还原除鳞的冷轧带钢退火后内部组织发生了回复、再结晶和晶粒长大现象,退火温度越高,退火时间越长,晶粒长大越严重。与酸洗除鳞的冷轧带钢不同,经过氢还原除鳞的冷轧带钢再结晶退火时间相应缩短,在相同条件下,退火后基体晶粒尺寸相对较大,表面脱碳层内的晶粒长大更为明显,其抗拉强度降低10～20 MPa,伸长率提高3%～5%。     

AZ91镁合金旋转喷吹除气理论分析及实验研究

通过分析旋转喷吹除气过程中氢在惰性气泡表面和金属熔体/空气界面的质量传输,建立适用于镁合金旋转喷吹除气的理论模型.通过计算,分析工艺参数对除气效率的影响.结果表明:随着旋转喷吹转速由230 r/min增大到330 r/min时,熔体中气泡总表面积由1.49×10-2m2增大到3.44×10-2m2,这增大了熔体中氢向气泡的单位时间扩散量,从而使除气效率随着转速的增加而增大.利用减压凝固方法对旋转喷吹除气的效果进行实验验证,实验结果与理论模型计算结果吻合较好.该模型可以用来指导镁合金熔体除气工艺的优化.     

超声频率对铝熔体除气影响的试验研究

在不同温度区间下向99.7%的工业纯铝和7050铝合金熔体中施加频率分别为15kHz和20kHz的相同功率超声波,利用 HYSCANⅡ测氢仪测量每次试验后熔体中的氢含量,进而探讨频率对铝熔体超声除气的影响规律及其作用机制。试验表明,超声作用能显著降低铸锭中的氢含量;熔体氢含量随着温度的升高而增大;熔体温度在660～720℃之间时,温度越低,除气效果越好,但是温度对除气效率影响不大;在相同功率和温度下,频率为15kHz的超声除气效率和除气效果都明显好于20kHz的。超声空化效应对产生大量的空化泡起着关键作用,超声频率对空化泡的长大以及熔体中氢的扩散具有重要作用。     

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.     

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.     

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。     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.