Numerical simulation for mold-filling of thin-walled aluminum alloy castings in traveling magnetic field

1 .IntrOdUction High一strength,light一weight and large一size alumimimalloy eastings are widely used in aviation,astronavigation,gUided missile and 50 on.With the develoPment of neweasting teehnology,it 15 imPortant     

INFLUENCE OF STRESS STATE IN EARING PREDICTION (Ⅱ) CRYSTALLOGRAPHIC ANALYSIS OF BCC METALS

ＩＮＦＬＵＥＮＣＥＯＦＳＴＲＥＳＳＳＴＡＴＥＩＮＥＡＲＩＮＧＰＲＥＤＩＣＴＩＯＮ（Ⅱ）ＣＲＹＳＴＡＬＬＯＧＲＡＰＨＩＣＡＮＡＬＹＳＩＳＯＦＢＣＣＭＥＴＡＬＳ①ＬｉＳａｉｙｉ，ＺｈａｎｇＸｉｎｍｉｎｇ，ＬｉＬｕｏｘｉｎｇＤｅｐａｒｔｍｅｎｔｏｆＭａｔ...     

Microstructure and properties of vacuum counter-pressure cast aluminum alloy

As a special casting process, counter-gravity casting has many advantages especially in producing thin-wall complicated castings and has widely been used in industry [1]. In recent ten years, various different counter-gravity casting processes have been continuously developed such as vacuum suction casting, low-pressure casting and counter-pressure casting [2-4] et al. Vacuum counter- pressure casting is a new kind of counter-gravity casting technology that was developed in recent years. It ha…     

Low-temperature superplasticity of ZK40 magnesium alloy processed using equal channel angular pressing

Microstructure evolution and superplastic behaviors of ZK40 magnesium alloy were investigated in the temperature range of 473～623 K. Transmission electron microscopy (TEM) was used to study the microstructure changes, twinning occurred significantly after being processed by equal channel angular pressing (ECAP) for one pass through the die, the mean grain size was 5.6μm. Finer grains can be obtained after further processing through ECAP, the average grain size of the alloy processed by ECAP for three passes was as low as 0.8 μ_m; this alloy exhibited low temperature superplasticity at 473～523 K, elongations obtained at the same initial strain rate of 1×10~(-3) s~(-1) were 260％ at 473 K and 612％ at 523 K, respectively. Corresponding values for the ZK40 alloy processed by ECAP for only one pass were 124％ at 473 K and 212％ at 523 K, respectively; poor superplastic behavior of this material was related to the long-range stresses associated with the non-equilibrium grain boundaries within the coarse grains. The incompatibility between fine and coarse grains was thought to be unfavorable to the improvement of superplasticity.     

An innovative tester system for measuring mechanical property of foundry molding sand

1 .Introduction Molding sand ProPerties are elosely relevant to castingquality.During molding Proeess,molding sand ProPertiesean direetly affeet the quality of molds ineluding strength,dimension aeeuracy of mold     

铜掺杂聚L-天冬氨酸修饰电极同时测定多巴胺和尿酸

用循环伏安法制备了铜掺杂聚L-天冬氨酸修饰玻碳电极,研究了多巴胺（DA）和尿酸（UA）在该修饰电极上的电化学行为,建立了同时测定DA和UA的新方法。在pH3．5的磷酸盐缓冲溶液中,扫描速率为120mV]s时,DA和UA在该电极上产生氧化还原峰,峰电位分别为Eps=0．429V、Epc=0．336V（DA）和Eps=0．617V（UA）,DA和UA的氧化峰分开达0．188V。采用循环伏安法（CV法）和示差脉冲伏安法（DPVs法）同时测定DA和UA的线性范围分别为：DA：3．00×10^-6-4．00×100mol／L、4．00×10^-5～1．00×10^-4mlo/L（CV）、3．00×10^-7～3．00×10^-6mol／L、3．00×10^-6—1．00×10^-5mol／L（DPVs）,UA：8．00×10^-6～5．00×10^-5mol／L、5．00×10^-5-2．00×10^-4mol／L（CV）、3．00×10^-7～5．00×10^-5mol／L、5．00×10^-5．2．00×10^-4mol／L（DPVs）;检出限分另U为8．0×10^-7mol／L、1．0×10^-6mol／L（CV）和3．0×10^-7mol/L、3．0×10^-7mol／L（DPVs）。用于人体尿液中DA和UA的同时测定,结果满意。     

基于丙烯酰胺与还原型谷胱甘肽加成反应对丙烯酰胺的电化学检测的研究

以多壁碳纳米管（MWCNT）-室温离子液体（RTIL）复合物修饰电极,基于丙烯酰胺与还原型谷胱甘肽的亲核加成反应,通过监测谷胱甘肽（GSH）氧化电流的变化对丙烯酰胺fAA）进行了间接检测。MWCNT—RTIL复合物明显提高了电极对谷胱甘肽的电流响应,灵敏度达498nAL／（μmol·cm^2）。丙烯酰胺的浓度与电流变化值在O．02～10μmol／L范围内呈良好的线性关系,检测限为20nmol／L。     

EFFECT OF FeON SURFACE REACTION OF Co_3Ti WITH WATER 0VAPOR

１　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｓｔｕｄｉｅｓｈａｖｅｄｅｍｏｎｓｔｒａｔｅｄｔｈａｔａｎｕｍｂｅｒｏｆｏｒｄｅｒｅｄｉｎｔｅｒｍｅｔａｌｌｉｃｓｃｏｎｔａｉｎｉｎｇｒｅａｃｔｉｖｅｅｌｅｍｅｎｔｓ，ｓｕｃｈａｓＡｌ，Ｔｉ，ａｎｄＳｉａｒｅｓｕｓｃｅｐｔｉｂｌｅｔｏｅｎｖｉｒｏｎｍｅｎｔａｌｅｍｂｒｉｔｔｌｅｍｅｎｔｗｈｅｎｔｅｓｔｅｄｉｎａｉｒａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅ．Ｔｈｉｓｐｈｅｎｏｍｅｎｏｎｉｓｂｅｌｉｅｖｅｄｔｏｂｅａｈｙｄｒｏｇｅｎｅｍｂｒｉｔｔｌｅｍｅｎｔｐ…     

介孔-大孔分布活性氧化铝的制备与表征

研究以Al2(SO4)3和NaAlO2为原料并流合成拟薄水铝石,经煅烧得到γ-Al2O3;分别考察了反应温度、反应液pH、反应物浓度和加入PEG对制备γ-Al2O3的比表面积、堆密度、孔容、孔分布的影响,采用X射线衍射、BET、压汞法等方法对γ-Al2O3进行了表征,制备出符合长链烷烃脱氢催化剂所用的介孔-大孔分布的活性氧化铝载体.表征结果显示,制备适宜介孔-大孔孔径分布的γ-Al2O3的较好条件为:反应液的pH为7、反应温度为70℃、NaAlO2的浓度为123 g/L、Al2(SO4)3的浓度为56 g/L 、反应时间为1 h、老化时间为2 h、700℃下煅烧.