微重力偏晶合金凝固特征SCIEI

对在微重力条件下获取的Al-In(95wt-%)偏晶合金的显微组织特征进行了分析,结果表明,在空间制取的试样的Al枝晶中,还存在着大量的In质点;并且这些质点的分布具有某种规律性,由此形成了与地基样品显微组织上的明显差异,反映出一种与重力效应相关的材料凝固特性。     

高温度梯度下Al-In偏晶合金定向凝固组织的演化规律

应用高温度梯度的方法，研究了在定向凝固条件下温度梯度与凝固速率的比值G／R对Al-17．5％In(质量分数)合金凝固组织的影响．结果表明，偏晶合金的定向凝固与共晶合金定向凝固的生长规律类似．在高温度梯度下，仅在很低的生长速度时才能形成二相有序排列的共生．在偏晶合金定向凝固进入稳态生长以后，在各自的相凝固前沿富集了另一相的溶质，由于两相的层间距不大，长大过程中的横向扩散占主导地位．随着生长速度的增大或温度梯度的降低，Al-17．5％In合金定向凝固组织从纤维结构到周期性或规则排列的串状结构再到弥散分布结构转变．这种转变与固一’液界面形状的转变有密切关系．     

磁场作用下Al-Pb偏晶合金的凝固过程

在恒定磁场作用下对Al-Pb合金进行定向凝固实验, 考察了合金成分、凝固速度、恒定磁场对凝固组织的影响. 模拟研究了恒定磁场作用下Al-Pb合金定向凝固组织的形成过程, 分析了磁场的影响机理和合金成分、凝固速度、磁场强度对弥散型凝固组织获得的影响. 模拟和实验均表明恒定磁场促进弥散型偏晶合金凝固组织的形成.     

(Fe-10Ge)-O偏晶系的激光快速熔凝

利用激光熔化、基体自淬火实现快速凝固,能有效地抑制偏析而得到均匀组织。但是,我们发现固溶态Fe-10Ge合金经激光处理后反而出现大量球状第二相颗粒,其它低碳铁基合金也有类似现象。本文对此作了研究,确认这是由于铁基合金与氧形成偏晶系而出现的偏晶转变现象。试样由工业纯Fe(含C0.018%以下)和高纯10%Ge经真空电弧炉冶炼而得。连续波激光束以     

用铜模快冷法制备均质Al—In过偏晶合金

采用铜模快冷工艺制备了均质的Al-In过偏晶合金，分析了合金熔配过程、合金成分以及冷却速率对显微组织的影响。研究结果表明，对于质量分数不大于30％In的合金成分，1173K时保温40min以上时可得到均匀的单一合金熔体。采用铜模快冷方法可以得到第二相颗粒均匀分布的至少4mm厚的均质合金薄板。In颗粒尺寸分布具有双峰分布形式。随着In含量的增加或薄板厚度的增大即冷却速率的降低，In颗粒的平均尺寸增大。     

二元系液相分层规律及会溶和偏晶温度的预报

固相生成金属间化合物的液相分层二元系在Ｍｉｅｄｅｍａ的Δ—Δｎｗｓ１／３图中,分布在Δ＞１．３的区域,然而在该区域混杂有固相没有金属间化合物的液相分层二元系。为了消除这种混杂现象,应用扩展的Ｍｉｅｄｅｍａ合金元胞模型研究了金属液相分层二元系固相能否生成金属间化合物的规律。在由原子参数Δ与Δｎｗｓ１／３及ΔＺ张成的多维空间中,上述两类二元系各自分布在特定的区域。据此结果,以Δ,Δｎｗｓ１／３,ΔＺ,ＲＡ／ＲＢ作为人工神经网络的输入特征量,采用误差反向传递算法,利用经已知样本集训练的人工神经网络对上述二元系的会溶温度和偏晶温度进行预报。预报结果与实测结果符合较好     

STRUCTURAL EVOLUTION OF UNDERCOOLED SINGLE-PHASENi-2wt%Pb MONOTECTIC ALLOY

1. IntroductionDendrite is the common growth manner of undercooled single-phase alloys, and recentinvestigations['] revealed that there are three critical undercoolings, ATI, ATZ and aT3,during the solidification process of this kind of alloys. Within the undercooling range of aTIand aT2, the solidification structure undergoes the first change from common dendrites, (less than ATI) to the first class granular grains (higher than aTI). When the undercoolingis higher than aT2, the change f…     

连续凝固偏晶合金薄带凝固组织进化过程模拟

分析了偏晶合金薄带垂直连续凝固过程,发展了描述该条件下偏晶合金凝固组织演变的数学模型,将计算的温度场和浓度场与凝固组织演变的控制方程相耦合,模拟了Al-5Pb(质量分数．%)合金的凝固过程．结果表明．在固/液界面前存在一过冷区、弥散相液滴在此区间内形核,这些液滴在移向凝固界面的过程中进行扩散长大,随着凝固速度的提高,形核率升高,弥散相液滴的数量密度增大．平均半径减小。     

COLLISION COARSENING OF DISPERSION DROPLETS IN SOLIDIFICATION PROCESS OF MONOTECTIC ALLOY

ＣＯＬＬＩＳＩＯＮＣＯＡＲＳＥＮＩＮＧＯＦＤＩＳＰＥＲＳＩＯＮＤＲＯＰＬＥＴＳＩＮＳＯＬＩＤＩＦＩＣＡＴＩＯＮＰＲＯＣＥＳＳＯＦＭＯＮＯＴＥＣＴＩＣＡＬＬＯＹ￥ＺｈａｏＪｉｕｚｈｏｕ；ＧｕｏＪｉｎｇｊｉｅ；ＪｉａＪｕｎ；ＬｉＱｉｎｇｃｈｕｎ（Ｓｃｈｏ...     

快速凝固Al-In偏晶合金的显微结构

采用单辊法快速凝固工艺制备均质的Ａｌ－Ｉｎ偏晶合金,并对所获得的快速凝固组织和形貌进行了观察和研究。结果表明,细小的Ｉｎ颗料均匀分布在Ａｌ基体中：在甩带厚度方向上,随着与激冷面距离的增大,Ｉｎ颗粒尺寸逐渐增大;在同一辊速条件下（同一冷却速率）,随着Ｉｎ含量的增加,Ｉｎ颗粒的平均尺寸也不断增大;同一成分条件下,随着辊速的升高,Ｉｎ颗粒的平均尺寸不断减少;单辊法快速凝固过程中第二相液滴通过Ｂｒｏｗｎｉ     

非过渡金属二元系液相分层的若干规律

用扩展的Ｍｉｅｄｅｍａ合金元胞模型研究了非过渡金属二元系液相分层规律，结果表明：Δｎｗｓ＾１／３大，Δψ小的二元合金系液相分层，在ΔＺ（价电子数差）与Δｎｗｓ＾１／３，Δψ张成的三维空间中，形成固相中化合物的二元液相分层系和不形在固相中间化合物的液相分层系各自分布在特定的区域。     

Ti-47Al合金籽晶法定向凝固过程中的组织演化

以Ti-43Al-3Si为籽晶,对Ti-47Al合金籽晶法定向凝固过程中的相选择和组织演化规律进行了研究.凝固初期,液相中富含Si,促使α相为其初生相,获得了与生长方向平行的全片层组织.随着凝固的进行,液相成分逐渐接近Ti-47Al.生长速率为90 mm/h时,凝固组织以胞状树枝晶形态生长,由于晶体生长形态对界面前沿溶质分布的影响,在稳定的溶质边界层建立前,Al和Si含量不能保证α相的连续生长,β相在α枝晶间形核长大,出现与凝固方向成45°夹角的片层,破坏了片层取向的一致;生长速率增至720 mm/h时,凝固组织中枝晶生长发达,枝晶间距减小,基本转变为以择优取向生长的α相.     

7050合金显微结构分析SCIEI

本文用常规透射电子显微术,动力学衍射模拟技术研究了7050铝合金在T74热处理制度下的各种显微结构。研究发现,合金中主要有Al_3Zr超点阵相,η′相和Al_4Cu_2Fe夹杂相。η′相具有C心正交结构,点阵常数a=0.492nm,b=0.852nm,c=0.701nm.与基体间取向关系满足(101)m∥(010)η′,[111]m∥[001]η′。     

A MICROSTRUCTURAL ANALYSIS OF 7050 Al ALLOY

The microstructure of 7050 AI alloy in T74 condition has been studied by means of transmis-sion electron microscopy and dynamical diffraction simulation.It was found that the alloystudied contains mainly AI3Zr superlattice phase,η′-phase and Al_7Cu_2Fe constituent phase.The η′-phase has an orthorombic crystal structure with a=0.492 nm,b=0.852 nm andc=0.701 nm.The orientation relationship between the η′-phase and matrix was determinedas(101)_m∥(010)_(η′)[111]_m∥[001]_(η′)     

SOLIDIFICATION OF Zn－Pb ALLOY UNDER SIMULANT MICROGRAVITY CONDITION OF ORTHOGONAL ELECTRIC AND MAGNETIC FIELDS

ＳＯＬＩＤＩＦＩＣＡＴＩＯＮＯＦＺｎ－ＰｂＡＬＬＯＹＵＮＤＥＲＳＩＭＵＬＡＮＴＭＩＣＲＯＧＲＡＶＩＴＹＣＯＮＤＩＴＩＯＮＯＦＯＲＴＨＯＧＯＮＡＬＥＬＥＣＴＲＩＣＡＮＤＭＡＧＮＥＴＩＣＦＩＥＬＤＳ￥Ｚｈａｏ，Ｊｉｕｚｈｏｕ；Ｇｕｏ，Ｊｉｎｇｊｉｅ；Ｊｉ...     

MICROSTRUCTURAL FORMATION MECHANISM OF SEMI-SOLID AZ91D ALLOY

With the help of an electromagnetic stirring device and alloy melt quenching technology, the microstntcture of semi-solid AZqlD magnesium alloy slurry stirred by a rotationally electromagnetic fieM was studied and the experimental results are shown as the following. The primary α-Mg grains are refined obviously when the slurry is stirred by a rotational electromagnetic field during continuously cooling and they are eventually changed to fine rosette grains or spherical grains. If the above semi-solid slurty is further stirred isothermally for some time, much more spherical primary α-Mg grains can be obtained. If the melt is first cooled down to a given semi-solid temperature and then starts being stirred by the rotational electromagnetic field, the primary α-Mg dendrites will be large, and a longer time will be taken and a larger stirring power will be needed for the secondary army of the dendrites to be remelted on the roots to prepare an ideal semiolid slurry. Theoretical analysis indicates that the strong flow motion leads to a more even temperature field and a solute field and stronger man-made temperature fluctuation in the AZglD magnesium alloy melt so that the spherical primary α-Mg grains are increased in the slurry. Moreover, all the measures promoting the temperature fluctuation will be favorable to the formation of spherical primary α-Mg grains and all the factors increasing the arm＇s root remelting difficulty will be favorable to the formation of rosette-type primary α-Mg grains.     

MICROSTRUCTURAL EVOLUTION OF AS-CAST ZA27 ALLOY DURING COMPRESSIVE CREEP

Phase transformation and micro structural change of an as-cast ZA27 alloy were investigated during compressive creep by X-ray diffraction technique, SEM and TEM. Compressive creep induced decomposition of α metastable η' phase and a four-phase transformation, α + ε → T' + η and T' → θ, occurred during the compressive creep testing. The occurrence of negative creep in the alloy resulted from the volume expansion caused by the four-phase transformation. A micro structural change was also observed from a lamellar structure into a spheroidized structure in higher creep strain of tested specimens. It provided evidence of compressive creep induced phase transformation which occurred in ageing process.     

Microstructures of rapidly solidified Al-In immiscible alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒｅａｒｅｍａｎｙｂｉｎａｒｙｉｍｍｉｓｃｉｂｌｅｓｙｓｔｅｍｓｗｉｔｈａｍｉｓｃｉｂｉｌｉｔｙｇａｐｗｈｉｃｈｈａｖｅｂｅｅｎｉｄｅｎｔｉｆｉｅｄａｓｄｅｓｉｒ ａｂｌｅｆｏｒｍａｎｙａｐｐｌｉｃａｔｉｏｎｓ ,ｓｕｃｈａｓｅｎｇｉｎｅｅｒｉｎｇａｎｄｅｌｅｃｔｒｏｎｉｃｍａｔｅｒｉａｌｓ ,ｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｕｐｅｒｃｏｎｄｕｃ ｔｏｒｓ,ａｎｄｓｅｌｆ ｌｕｂｒｉｃａｔｉｏｎｂｅａｒｉｎｇｓ[1～ 3] .Ｈｏｗｅｖｅｒ ,ｔｈｅｆａｂｒｉｃａｔｉｏｎｏｆｓｕ…     

快速凝固TiAl基合金微晶的显微组织

用气体雾化方法制备了Ti-34Al-2Mn合金的微晶粉末,粉末典型粒度为27μm。X射线衍射结果表明,快冷态的粉末主要由α_2相和少量γ相组成。金相组织显示出等轴块状晶粒和树枝状结晶两种形态。经900℃,2h真空退火后,大部分α_2相转变成γ相,使原来的组织更加细化。     

MICROSTRUCTURE OF A RAPIDLY SOLIDIFIED Fe-C-Sn ALLOY

The microstructure of a laser-melted Fe-4% C-10% Sn alloy has been studied.Anon-crystalline phase was found in the upper part of the laser-melted zone:At the bottom ofthe melted zone,however,the microcrystalline zone which consists of α-Fe and a bet phasewas observed.Fine twinning martensite exists in the other area of the melted zone.