Kinetics of absorbing hydrogen of A1 melt

The kinetics process of absorbing hydrogen of Al melt was analyzed and it was considered that the concentration of hydrogen in Al melt was determined by the concentration of water vapor in the interface of the oxide layer and Almelt. The change of the alloying composition will result in the change of compactability of oxide layer and affect the process of the water vapor gas penetrating the oxide layer and entering the interface of Al melt and oxide layer. Based on theabove analysis, the kinetics equation of Al melt absorbing hydrogen was established, and compared with the test result.The results of calculation were elementally coincident with the test result. The curve of hydrogen concentration varyingwith reaction time in Al melt can be obtained from this equation. And scientific basis could be provided to select meltingtechnology parameter properly and control the concentration of hydrogen in Al melt.     

Hydrogen heat treatment of hydrogen absorbing materials

This study introduces the hydrogen heat treatment of hydrogen absorbing materials and its applicability for practical use. This treatment is somewhat different from normal heat treatment because of the interaction between metal atoms and hydrogen. Since hydrogen can be removed very fast by pumping it out the hydrogen-induced new lattice phase which can not be obtained without hydrogen can be preserved in a meta-stable state. A thermodynamic interpretation of the hydrogen heat treatment established previously was reformulated for graphical and analytical methods and applied to Pd-Pt-H and Pd-Ag-H alloy systems and a fair correlation between the calculation and experimental results was shown. The feasibility of applying the thermodynamic interpretation to intermetallic compounds-hydrogen systems was also discussed.     

在线式连续测氢仪在铝熔体表面吸氢特性研究中的应用

介绍了国内最新在线式连续测氢仪（ELH-IV）的测氢原理和结构。利用ELH-IV型快速测氢仪可在线连续测氢的特点,测量不同的熔体温度、保温时间以及熔体初始氢含最等工艺参数条件下铝熔体的表面吸氧情况,并分析了各参数对铝熔体表面吸氢特性的影响。     

Establishment of hydrogen measurement system for magnesium alloy melt

The equations of hydrogen solubility in pure magnesium and its alloy were deduced based on thermodynamic analysis： for pure magnesium, lgc（H）=0.51g p（H2）-1 332/T＋0.568; for AZ91 alloy, lgc（H）=0.51g p（H2）-1 332/T＋0.483. Based on the above equations, a rapid and reliable measurement system for hydrogen content in magnesium melt was set up with CPU controller and electric circuit..With this instrument, measurement experiments were carried out to determine hydrogen content in AZ91 melt. The results show that the actual hydrogen level of AZ91 melt under gas protection varies from 0.06 mL/g to 0.14 mL/g at the temperature range from 650 ℃ to 750 ℃ and hydrogen content lineally increases with the increase of temperature.     

Change law of real vapor pressure of Al element in Ti-xAl （x = 25～50） melt during ISM process

A new model was established to calculate the real vapor pressure of the AI dement in the molten Ti-xAl (x=25～50, mole fraction, % ) alloy. The effects of the holding time, chamber pressure, mole fraction of AI and melting temperature on the real vapor pressure of AI element in the vacuum chamber were analyzed. Because of the impeding effect of the real vapor pressure on the evaporation loss rate, within a short time (less than 10s), the real vapor pressure tends to a constant value. When the chamber pressure is less than the saturated vapor pressure of the AI component, the real vapor pressure of Al is equal to the chamber pressure. While when the chamber pressure is larger than the saturated vapor pressure, the real vapor pressure is equal to the saturated vapor pressure of the Al element of the same condition.     

Weibull verification of reduced pressure test as a tool for assessing Al melt quality

The credibility of reduced pressure test (RPT) as a substitute for Weibull analysis for benchmarking bifilm defects in Al alloys was confirmed by comparing the RPT parameters (2D and 3D porosity, and Bifilm Index) with the Weibull moduli for UTS values for pure Al and Al-0.05Sr alloys. The porosity of RPT samples was found to have an exponential decay relationship with Weibull modulus. A reasonable trend for Bifilm Index could not be found. 3D porosity of RPT samples was found to be more favourable than 2D porosity or Bifilm Index. Some evidence was also found of connections occurring between the sides of bifilm defects at the surfaces of the fractured tensile test bars of Al-0.05Sr alloy which had a relatively high UTS.     

Effect of dissolved hydrogen on removal of double oxide film defects from Al melt

Abstract

Effect of increasing the hydrogen content of the melt on the removal of double oxide (bifilm) defects in commercial purity Al melt was investigated using Weibull statistical analysis of mechanical properties of solidified castings and a semiempirical mathematical model that had been developed previously. The results of the Weibull analysis revealed that increasing the H content of the melt from 0·2 to 0·4 mL/100 g and holding the melt in furnace for 30 min caused the Weibull modulus of the casting to increase by ～73%. Studies (SEM and EDX) of fracture surfaces of the test bars indicated that the number of oxide defects in the melt decreased due to this treatment. The mathematical model suggested that increasing the H content of the melt to ～0·8 mL/100 g would force all the oxide defects to expand rapidly and float out of the liquid metal in a very short time.     

Effect of melt superheat on microstructure of Al4Fe2Mn1.5 Monel alloy

The effect of melt superheat on microstructure of Al4Fe2Mn1.5 Monel alloy made by vacuum melting method was studied. The results show that the alloy consists of dendritic γ matrix and γ′ phase, wherein γ′ phase has two morphologies at different melt superheat. One is divorced eutectic γ′ which distributes in the interdendritic area, the other distributes dispersedly in single particle on the dendritic arm and exists in the petalform shape in the transition area between dendritic arm and interdendritic area. With the increase of superheat, the dendrite becomes finer, the primary dendritic arm is melted off and the secondary dendritic arm spacing decreases. The size of γ′ phase distributed on the dendritic arm becomes smaller and the divorced eutectic γ′ phase increases.     

Separation efficiency of alumina particles in Al melt under high frequency magnetic field

The effects of separation time and magnetic induction intensity on the separation efficiency of alumina particles with diameters varying from 30 to 200 μm in aluminum melt were investigated. The experimental results show that the particle-accumulated layer is formed in the periphery of the solidified specimen when the diameter of the separated molten metal, the magnetic induction intensity and the separation time are 10 mm, 0.04 T and 1 s, respectively. When the separation time is 2 s, the particle-accumulated layer can be observed obviously and the separation efficiency is about 80%. There are few alumina particles in the inner of the solidified specimen when the separation time is 3 s. The separation efficiency higher than 85% can be achieved when the separation time is longer than 3 s. When the magnetic induction intensity is 0.06 T, the visible particle-accumulated layer can be formed in 1 s and the separation efficiency is higher than 95%. The experimental results were compared with the calculated results at last.     

In-situ synthesized (Al_3Zr+Al_2O_3)_p /A356 composites by direct melt reaction in Al-Zr-O system

1　INTRODUCTIONRecently ,muchattentionhasbeen paidtothedevelopmentofeffectivefabricationprocessesforpar ticulatereinforcedmetalmatrixcomposites (PRMM Cs) [13] .However,metalmatricesreinforcedwithparticlesformedinsituareanemerginggroupofdis continuouslyreinforcedcompositesthathavedistinctadvantagesovertheconventionalcomposites[4 ,5] .Inthein situfabricationprocess ,thespontaneousreac tionbetweenthereactantsisutilizedtosynthesizethereinforcementsinthemetalmatrix .Especially ,thedirectmelt…     

Effects of solid deformation and melt vibration on structure and refining performance of Al5Ti1B master alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＧｒａｉｎｒｅｆｉｎｅｍｅｎｔｏｆｆｅｒｓｓｕｂｓｔａｎｔｉａｌｂｅｎｅｆｉｔｓｉｎｂｏｔｈｃｏｎｔｉｎｕｏｕｓｃａｓｔｉｎｇｂｙｄｉｒｅｃｔｃｈｉｌｌ (ＤＣ)ａｎｄｉｎｃａｓｔ ｔｏ ｓｈａｐｅｐｒｏｄｕｃｔｓ[1].Ａｌ 5%Ｔｉ 1 %Ｂｍａｓｔｅｒａｌ ｌｏｙ ,ｗｈｉｃｈｍａｉｎｌｙｃｏｎｔａｉｎｓＴｉＡｌ3ａｎｄＴｉＢ2 ｐａｒｔｉｃｌｅｓｉｎＡｌｍａｔｒｉｘ[2 ,3]ｈａｓｂｅｅｎｐｒｏｖｅｎｔｏｇｉｖｅｔｈｅｂｅｓｔｇｒａｉｎｒｅｆｉｎｅｍｅｎｔ[4 ,5 ].Ａｄｄｉｔｉｏｎｏｆ 0 …     

Thermodynamics of effect of modification on microstructure o f Al-Si alloy melt

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｏｄｉｆｉｃａｔｉｏｎｏｆｐｈａｓｅＳｉｈａｓｂｅｅｎｕｓｅｄｗｉｄｅｌｙａｓａｎｅｆｆｅｃｔｉｖｅｗａｙｔｏｉｍｐｒｏｖｅｔｈｅｐｒｏｐｅｒｔｉｅｓｏｆＡｌＳｉａｌｌｏｙ.Ｂｕｔｔｈｅｓｔｕｄｉｅｓｏｎｔｈｅａｃｔｉｎｇｂｅｈａｖｉｏｒｏｆｍｏｄｉｆｉｃａｔｉｏｎｅｌｅｍｅｎｔｓｉｎｔｈｅａｌｌｏｙｈａｖｅｎｏｔｂｒｏｋｅｎａｗａｙｆｒｏｍｔｈｅｅｘｐｅｒｉｍｅｎｔａｌｐａｔｔｅｒｎ,ｉｎｗｈｉｃｈｔｈｅｍｏｄｉｆｉｃａｔｉｏｎｅｆｆｅｃｔｗａｓｅｖａｌｕａｔｅｄｏ…     

Electrochemical hydrogen absorbing properties of graphite/AB5 alloy composite electrode

Graphite is an inexpensive carbon material, but its hydrogen absorbing performance has attracted little attention. In this paper, in order to lower the cost of nickel metal-hydride (Ni-MH) battery, graphite is used as a hydrogen absorbing material in its negative electrode. The results of charge-discharge tests show that the graphite electrode has poor electrochemical hydrogen absorbing performance. The capacity of the graphite/AB₅ alloy (90 wt%) composite electrode is close to AB₅ alloy (298 mAh/g), but it has higher charge-discharge polarization and difficulty in activation. When graphite is modified with metal nickel powder by a simple ball milling process, the capacity of the composite electrode reaches to 315 mAh/g and its activation is accelerated. The results of electrochemical impedance spectroscopy (EIS) tests show that hydrogen diffusion in the modified composite electrode is more rapid than in AB₅ alloy, thereby resulting in lower charge-discharge polarization and better discharge performance at large currents.     

熔体处理在制备Mg-9Zn-2Al镁合金半固态浆料中的作用

采用自孕育法制备新型Mg-9Zn-2Al高锌镁合金半固态浆料,研究孕育剂加入量为5%(质量分数)、导流器角度为45°时熔体处理温度对Mg-9Zn-2Al镁合金组织的影响。对孕育剂加入熔体后的熔化状况进行分析,并从原子团簇角度探讨熔体处理温度对一次孕育的作用机理。结果表明:熔体处理温度过高或过低时,组织平均晶粒尺寸较大;在695~710℃范围内,晶粒平均尺寸较小,约为47.5~48.8μm。根据所推导出的孕育剂在导流器入口处的温度表达式,可以确定自孕育法铸造的最佳熔体处理温度,提出用固相率fS描述自孕育剂的熔化状况。     

Co对MlNi4.3-xCoxAl0.7贮氢电极动力学性能的影响

详细研究了Ｃｏ 对ＭｌＮｉ４ ．３ － ｘＣｏｘＡｌ０ ．７（ ｘ ＝ ０ , ０ ．３ , ０ ．５ ,０ ．７ ,０ ．９ ,１ ．１ ,１ ．３） 贮氢电极的动力学特性的影响; 研究的动力学参数包括高倍率放电特性ＨＲＤ、交换电流密度Ｊ０ 、极限电流密度ＪＬ、对称因子β以及氢在α相中的扩散系数Ｄα。实验结果表明： 随着ＭｌＮｉ４ ．３ － ｘＣｏｘＡｌ０ ．７ 贮氢电极中Ｃｏ 含量的增大, 合金的高倍率放电能力迅速减小, 交换电流密度Ｊ０ , 极限电流密度ＪＬ, 对称因子β以及氢在α相中扩散系数Ｄα显著降低     

Variation of hydrogen level in magnesium alloy melt

M agnesium alloy is one of the lightest metals used in industry. It offers numerous merits in physical, mechanical and casting properties: high specific strength and stiffness, good castability suitable for high pressure die casting, low density, high damping capacity, good thermal and electrical conductivity etc. [1] However, microporosity in the castings reduces mechanical properties [2-4] such as ultimate strength, yield strength, ductility and fatigue resistance. There are mainly two viewp…     

铝熔体除氢过程动力学

研究了铝熔体除氢时的除气和再吸气过程。实验结果表明：铝合金熔体除氢后,静置一定时间才能达到最佳除氢效果,静置时间和熔体表面状态有关：除氢后立即扒去表面浮渣,静置5～6 min为最佳;带渣静置,一般为10～12min。 此基础上,建立了铝熔体中氢的动力学模型,并对除氢和再吸氢过程进行了理论分析。     

Electrical resistivity and structural heredity of hypereutectic Al-Si alloy melt

1　INTRODUCTIONAgreatamountofpracticeprovesthat ,aftertheoriginalchargesareremelted ,themeltstatehashereditaryeffectsonthesolidificationstructurenewlyobtained .Hereditycanbeconsideredfrom generalsenseasthetransformationofthesimilaritiesinthestructureorphysicalpropertiesfromtheoriginalob jectstothesecondaryones .Moreover ,itissuitablefordescribingpropertiesthatcorrelatewiththepro cesswhichthealloysamplesexperiencedinsteadofpropertiesofalloystatefunctions .Whilestudyingthestructuralheredity…     

Microwave absorbing mechanism of soft magnetic alloy Fe85Si2Al6Cr7

The powders of amorphous nanocrystalline Fe85Si2Al6Cr7 were prepared by high energy ball milling for different times, and measured by XRD and network analyzer. The results show that： 1） nanocrystalline microstructure remarkably improves the microwave permeability, and the permittivity is controlled effectively; 2） by adding proper dyeing auxiliary （such as copper phthalocyanine）, the magnetic properties of powders are improved when the particle sizes milled are excessively small.