STUDY ON THE SHOCK WAVE CRYSTALLIZATION OF AMORPHOUS ALLOYS BY DSC

Shock wave and annealing crystallization of amorphous alloys FeSiB, FeMoSiB and FeCuNbSiB were studied by isothermal and non-isothermal DSC technique. It was found that the shock wave crystallization is very perfect, the fraction crystallized is very close to 100%, though the period of crystallization is very short, only about 10-4-10-6s. Their produced phases differ from the parent phase in structure and composition. The high velocity of the transformation is very difficult to explain by the diffusion theory of solid state phase transition.     

INFLECTION OF COERCIVITY DURING LOCAL CRYSTALLIZATION OF Fe-Si-B AMORPHOUS ALLOYS

An inflection hehaviour was revealed during isothermal annealing under the observation oftransition of the coercivity of Fe-Si-B amorphous alloys during local crystallization.It maybe interpreted by the transition of α-Fe grain precipitated from single to multiple domain,Thus,the theoretical expression of H_0-t_a may be derived.The plot of expression H_0-t_a calcu-lated well represents the feature of the experimental curve.     

EFFECT OF PRE-ANNEALING ON CRYSTALLIZATION KINETICS OF AMORPHOUS Ni-P ALLOYS

The effect of pre-annealing treatment on the crystallization kinetics parameters of amorphous Ni-P alloys has been investigated.Experimental results showed that the crystallization tem- perature,T_p and T_x,the apparent activation energy,E_c,as well as the Avrami exponent for isothermal crystallization,n,decrease significantly,while ΔT_(px)=T_p-T_x increases with the elongation of pre-annealing time at 570 K.     

MAGNETIC PROPERTIES AND CRYSTALLIZATION OF AMORPHOUS ALLOYS Co_(90-x)Cr_xZr_(10)

Curie temperature of amorphous alloys Co_(90-x)Cr_x Zr_(10) decreases linearly with increas-ing x.Average magnetic moment per magnetic atom Co or Cr is 1.51 μB or -3.62 μBrespectively.The temperature dependence of spontaneous magnetization at low temper-atures is in agreement with Bloch's T~(3/2) law.The spin wave stiffness constant decreaseswith increasing x from 4 to 20.The range of interaction is 2—3 atoms for x=4 andnearest neighbour atom for x=20.The crystallization temperature increases mono-tonically with increasing x.It may relate to the average number of outer electrons peratom.The crystalline phase components of heat-treated alloys were analyzed by X-raydiffration and thermomagnetic measurement.     

A MATHEMATICAL EXPRESSION OF CRYSTAL GROWTH RATE DURING CRYSTALLIZATION OF AMORPHOUS ALLOYS

A mathematical expression of the crystal growth rate during crystallization of the amorphousalloys was derived from the micromechanism of crystallization newly developed by theauthors. Thus, the satisfactory explanation of the experimental results obtained by Nunogakiet al., Heimendahl et al. and the authors might be found. It seems also to be modelled with theexpression for the crystal growth and the crystal size influenced by time during thecrystallization of amorphous Ni-P alloy foil at in situ heating. Based on the expression, thefactors influencing the crystal growth rate, such as temperature, time and microstructure ofamorphous alloys have been discussed.     

EFFECT OF COMPOSITION ON PHYSICAL PROPERTIES OF AMORPHOUS Fe-Si-B ALLOYS

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ELECTROPLATING OF AMORPHOUS Al-Mn ALLOYS(Ⅱ) KINETIC FEATURES OF ELECTRODEPOSITION OF Al-Mn ALLOYS

ＥＬＥＣＴＲＯＰＬＡＴＩＮＧＯＦＡＭＯＲＰＨＯＵＳＡｌＭｎＡＬＬＯＹＳ（Ⅱ）ＫＩＮＥＴＩＣＦＥＡＴＵＲＥＳＯＦＥＬＥＣＴＲＯＤＥＰＯＳＩＴＩＯＮＯＦＡｌＭｎＡＬＬＯＹＳ①ＺｈａｏＧｕａｎｇｗｅｎ，ＺｈｕＴｅｎｇ，ＬｉｕＬｉａｎｙｕＤｅｐａｒｔｍｅ...     

A THERMODYNAMIC STUDY OF THE Fe-C SYSTEM——I. THERMODYNAMICS OF LIQUID Fe-C ALLOYS

作者在本文中综合分析了关於液态铁碳合金中碳活度测定的諸家研究结果並比较其优劣. 然后根据Richardson与Dennis用CO_2/CO平衡法的实验数据,用Darken与Smith的统计模型与最少假定,导出了液态鉄碳合金中α′_c与N′_c的关系(α′_c=logγ′_c,/(N_Fe′)~2,标准状态为石墨),并温度对此关系的影响.计算结果符合於(i)鉄液内石墨溶解度的实验数据;(ii)与用电动势法测定液态铁碳合金中碳活度的实验数据;及(iii)奥氏体、铁液、石墨共晶平衡的要求. 根据本文所导出的α′_c-N′_c曲綫,作者算得石墨在鉄液内的溶解热为3930卡;然后依此及其他必需数据,导出下列关系:C(石墨)=C[%],△F°=3930-9.21T. 最后作者从液态铁碳合金结构的观点讨论了图1中α′_c-N′_c曲綫的形状.     

THERMODYNAMIC STUDY OF BAINITIC TRANSFORMATION IN Fe-C ALLOYS

The growth of bainitic ferrite is a couple process of the shear transformation of Fe atoms withthe diffusion of C atoms.The diffusion growth of the ferrite is impossible when the tempera-ture is below 400℃,and the paraequilibrium shear growth may occur at the temperature be-low 550℃.This paraequilibrium shear growth model explains the overlap of the bainitescreated from two growth mechanisms at 400—550℃.     

DRIVING FORCE OF BAINITE TRANSFORMATION FOR Fe-C-Mn ALLOYS

The regular solution model developed by Hillert and Stanffanson is applied to calculate thedriving force for transformations with three possible mechanisms in the intermediate tempera-ture range between proeutectoid and martensite transformation.Focus is made on thethermodynamical discussions for both diffusional and shear mechanisms for bainitic transfor-mations in different temperature ranges.     

STRUCTURE AND GLASS FORMING ABILITY(GFA)OF AMORPHOUS ALLOYS

A new microstructure model is developed for amorphous alloys,so called Cluster medel,in which the amorphous phase is thought of composing of randomly distributed orderedclusters of different sizes.Thermodynamic calculation on this model deduces a parameterdescribing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,whereT_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpychange of melting.It is believed that easy glass forming alloy systems have larger valuesof a_c.This new criterion of GFA not only provides the theoretical background for severalGFA criteria in the literature cited,but also can predict the GFA of many alloy systemsmore reasonably and accurately.     

A PARAMETER FOR EVALUATING ABILITY OF GRAIN REFINEMENT OF SOLUTE ELEMENTS

The gradient of the equilibrium melting temperature distribution at the advancing liquid-solidinterface of liquid side was derived.From which,a parameter,H,used for evaluating the abili-ty of grain refinement of solute elements was proposed.Experiments on Al-based alloys showthat the grain size decreases as the value of parameter,H,increases.Such a dependance indi-cates that the parameter H can be used for choosing grain refiner.     

INVESTIGATION OF RAPID DIRECTIONAL SOLIDIFICATION OF AL-BASED IMMISCIBLE ALLOYSⅠ. EFFECT OF APPLIED MAGNETIC FIELD

在自制的具有磁场作用的快速定向凝固装置上,考察了磁场对Al-Bi难混溶合金凝固组织的影响,并从理论上分析了磁场对难混溶合金液-液相变过程中液滴形核、空间运动和碰撞凝并的影响.结果表明,在磁场作用下液滴的运动速度以及由运动导致液滴间碰撞凝并的概率得到有效降低;随着磁场强度的增加,合金组织中富Bi粒子平均尺寸减小,分布更弥散.     

THERMODYNAMICAL CALCULATION OF FORMATION ENTHALPIES FOR ALKALINE METAL ALLOYS

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THE EFFECT OF ENVIRONMENT WORK ON EFFECTIVE SEGREGATION COEFFICIENT OF SOLUTE AT SOLID／LIQUID INTERFACE

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HIGH-TEMPERATURE AC MAGNETIC PROPERTIES OF NANOCRYSTALLINE FINEMET ALLOYS WITH Co ADDITION

High-temperature AC magnetic properties for (Fe0.5Co0.5)73.5Cu1Nb3Si13.5B9 alloy annealed at various temperatures have been investigated using an impedance analyzer. Annealing temperature Ta has obvious effects on high-temperature AC magnetic properties of the alloy. The Hopkinson peak appears only in the amorphous alloy when Ta ≤ 703K. As Ta increases above 733K, the real part of the complex initial permeability μi' descends gradually, μi' decreases more slowly with temperature in the high temperature range. The high-temperature (about 750K) AC initial permeability for the alloy annealed at Ta=763K has been found to maintain a stable high value of 950 up to a frequency of ~ 1 × 105Hz. Partial substitution of Co for Fe in the Fe73.5Cu1Nb3Si13.5B9 alloy leads to an increase of around 110K of the Curie temperature of the amorphous phase, much higher than Ge-containing Finemet alloy.     

PREPARATION OF AMORPHOUS Mo_5Si_3 BY MECHANICAL ALLOYING AND THE CRYSTALLIZATION

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MICROSTRUCTURE STUDY OF CONSTITUENT PHASES IN 2024 SERIES Al ALLOYS

X-ray microanalysis,convergent beam electron diffraction(CBD)and selected area electrondiffraction(SAD)studies on the structures and compositions of the constituent phases in2024 series Al alloys have been conducted.Partial substitution of alloying elements is found tooccur in all the constituent phases,which cause small deviations from the stoichiometric com-positions reported in these ternary compounds.The dominant phase is α-Al_(12)(FeMn)_3Si whichhas a body center cubic crystal structure with the Im■ space group and a=1.25 nm.The nextdominant phase is Cu_2FeAl_7 which has a primitive tetragonal crystal structure with theP4/mnc space group and a=0.6336 nm,c=1.487 nm.The minor phase is α'-Al_(12)Fe_3Si hav-ing α primitive cubic crystal structure with the Pm■ space group and α=1.27 nm.     

APPLICATION OF MOLECULAR ORBITAL THEORY TO ANALYSIS OF PHASE STABILITY FOR ALLOYS

The critical _d vahues ( _ ) of the γ/(γ+σ).γ/(γ+μ) and γ/(γ+γ') phase boundaries insome ternar alloy phase diagrams at various temperatures are calculated by averaging the _d values of sererai selected characteristic points at the phase boundaries.Approxmateequations for the temperature dependence of the critical _d of γ/(γ+σ).γ/(γ+μ) andγ/(γ+γ') phase boundaries are established.The accuracy of the analysis is discussed in detail.It is found for the first time that the average value of the bondorder _ at the phase boundaries ts also approximatelr a constant and therefore a criticalaverage bond order _ like - can be introduced for the analysts of phase stability     

ELECTROPLATING OF AMORPHOUS Al－Mn ALLOYS （I） KINETIC FEATURES OF ELECTRODEPOSITION OF PURE Al

ＥＬＥＣＴＲＯＰＬＡＴＩＮＧＯＦＡＭＯＲＰＨＯＵＳＡｌ－ＭｎＡＬＬＯＹＳ（Ｉ）ＫＩＮＥＴＩＣＦＥＡＴＵＲＥＳＯＦＥＬＥＣＴＲＯＤＥＰＯＳＩＴＩＯＮＯＦＰＵＲＥＡｌ￥ＺｈａｏＧｕａｎｇｗｅｎ；ＺｈｕＴｅｎｇ；ＬｉｕＬｉａｎｙｕ（Ｄｅｐａｒｔｍｅｎｔｏｆ...