镍基单晶高温合金杂晶形成倾向性的研究

采用2种不同平台尺寸的模型试样,对镍基单晶高温合金定向凝固过程中的杂晶形成倾向性进行量化研究,对不同合金的杂晶形成倾向性及杂晶在平台内的形成机制进行探索.结果表明,平台长度越长、高度越小时,杂晶越容易在平台内形核并长大;在第一、二、三代镍基单晶高温合金SRR99,DD5和DD90中,第一代合金的杂晶形成倾向性最弱,第二代次之,第三代最强;凝固时平台尖角处的过冷度大于平台内部的过冷度,且随着平台长度增加和平台高度减小,平台尖角处的过冷度增大,当平台尖角处的过冷度达到临界形核过冷度时,杂晶在平台尖角处形核并快速长大进入平台内部.     

几种镍基高温合金的过冷能力和单晶可铸性的研究与比较

对6种镍基高温合金熔体在陶瓷型壳中的凝固行为进行了检测,得出了各种合金的液相线温度T_L、临界形核温度TN和临界形核过冷度ΔT_N=T_L-T_N,发现它们具有明显不同的过冷能力。在单晶叶片的铸造实验中,具有高过冷能力(高于40℃)的合金在宏观上抗杂晶能力最强,但容易形成枝晶碎臂微观缺陷。具有中等过冷能力(20～30℃)的合金,既能有效防止宏观杂晶缺陷的发生,又能避免微观碎晶的形成,显示出最佳的单晶可铸性。而具有很低过冷能力(低于10℃)的合金,抗杂晶能力非常弱,表现出很差的单晶可铸性。镍基高温合金具有相似的化学成分,却显示出明显不同的过冷能力和单晶可铸性,对其原因还需要做进一步的研究。     

镍基单晶高温合金DD11杂晶形核的热力学研究

以单晶叶片在研制过程中常出现杂晶而导致产品不合格为研究背景,以DD11合金单晶叶片缘板杂晶为研究对象,通过测试叶片缘板在定向凝固中的冷却速率,借助差热分析法(DSC)以相同冷却速率条件下测定DD11合金的形核临界过冷度及熔化潜热。利用扫描电镜(SEM)观察合金与型壳之间界面的化学反应情况,采用液滴法测量了合金熔体与型壳的润湿角,并完成了合金固液界面能及杂晶形核功的定量分析。结果表明,DD11合金与型壳基体属不润湿系统,润湿角为145.47°;DD11合金单晶叶片缘板杂晶形核临界半径为43.07 nm,临界形核功为0.938×10~(-15) J;较大的合金异质形核临界过冷度及合金熔体与型壳的润湿角有利于减少杂晶的产生。本研究对控制单晶叶片杂晶形核及提高产品合格率具有一定理论指导意义。     

过冷DD3单晶高温合金凝固组织演化

用复合熔盐净化与循环过热相结合的方法,研究了ＤＤ３单晶高温合金过冷熔体凝固组织的演化规律,获得了最大过冷度２１０Ｋ,在所获得的过冷度范围内,其凝固组织的形态发生三次突变;第一次是在过冷度为３０Ｋ时,因枝晶熟化,重熔,高度发牵树枝晶转变为第一类粒状晶;第二次发生在过冷度为７８Ｋ时,因枝晶熟化抑制,组织转变为细枝晶;当过冷度大于等于１８０Ｋ时,组织因枝晶发生碎断和再结晶而转变为第二类粒状晶     

偏晶合金Ni—31.44％Pb过冷组织粒化机制

利用溶融玻璃净化、循环过热相结合的方法对Ni-31.44%Pb(质量分数）偏晶合金宽过冷区间组织演化规律进行研究。结果表明：随过冷度的增大,凝固组织发生三次转变。其中当△T＞242K时,合金组织发生第三次转变,由细密枝晶骤燃粒化为过冷粒状晶。通过组织观察和过冷熔体枝晶生长过程的理论计算发现,快速凝固过程中液相变速率骤然增加,引起枝晶全面碎断,然后在枝晶块表面能和就变能的驱动下,晶界移动,发生碎晶合并－再结晶是形成过冷粒状晶的原因。     

深过冷铁钴基块体合金的细晶化研究

采用熔融玻璃净化与循环过热相结合的深过冷技术,对比研究了深过冷凝固和过冷熔体Cu模激冷凝固Fe₄₄Co₄₄Nb₇-B₄Cu₁块体合金的组织特征.结果表明,随过冷度增大,深过冷和深过冷Cu模激冷凝固组织均由最初的发达树枝晶逐渐演变为细小的粒状晶,并且Cu模激冷可显著减小树枝晶向粒状晶转变的临界过冷度.在相同过冷度下,过冷熔体Cu模激冷凝固组织更加细小均匀,其根本原因在于Cu模激冷和熔体深过冷的双重作用不仅提高了熔体的形核率并抑制了晶粒长大,而合金化元素在晶界聚集并不是阻碍晶粒长大的主要原因.     

过冷DD3单晶高温合金凝固组织细化的再结晶机制

用复合熔盐净化与循环过热相结合的方法,在0－210K过冷度范围内,研究了DD3单晶有高温合金凝固组织形态溶化过程,当地冷度△T超过△T5（153K）时,枝晶组织开始生变形、碎断,当△T超过△T^*（180K）时,组织完全转变为第二类粒状晶,粒化过程中位错及其它晶体缺陷的形态演变化表明,△T^*以上的晶粒细化是由再结晶机制控制的。     

深过冷Fe-80at%Ni凝固组织

采用熔融玻璃与循环过热相结合方法使Fe-80at%Ni合金熔体获得了340K的大过冷,对Fe-80at%Ni过包晶合金在宽过冷范围内凝固组织进行研究。结果表明：在小过冷范围（ΔT〈28K）,凝固组织为普通树枝晶;当28K〈△T〈54K时,凝固组织为不规则粒状晶;当54K〈△T〈70K时,凝固组织为树枝晶;当70K〈△T〈210K时,凝固组织转变为细小的粒状晶;当△T〉210K时,凝固组织为粗大的晶粒。随着过冷度的增加,凝固组织发生了两次粒化和一次粗化过程,分别为由小过冷树枝晶向第一类粒状晶的转变,由大过冷树枝晶向第二类粒状晶的转变和由细小粒状晶向粗大晶粒转变。粒化机理分别是枝晶重熔,枝晶碎断＋再结晶和极大的表面能导致小晶粒合并。     

深过冷A172Ni12Co16合金的组织演化及单相准晶的生成

采用惰性形核涂层型壳和氩气保护下循环过热的深过冷方法，系统研究了深过冷条件下A172Ni12Co16合金的凝固组织演化过程及单相准晶的生成条件。结果表明：在0-200K的过冷度范围内，随过冷度的增大，A172Ni12Co16合金发生小过冷树枝晶→柱状晶→等轴晶的组织转变，转变的两个临界过冷度分别为ΔT1＝60K和ΔT2＝120K；此外，当熔体过冷度大于60K时，准晶相在与晶体相的竞争形核中胜出，作为初始相从熔体中析出，并随过冷度的增大，凝固组织逐渐变为单相准晶。     

Ag-Cu/Co-Sn共晶合金深过冷快速凝固反常共晶的形成研究

利用熔融玻璃净化循环过热的方法进行了Ag-Cu/Co-Sn共晶合金的深过冷快速凝固实验,并系统研究了熔体过冷度和微量Nb添加对反常共晶形成的影响。结果表明,快速凝固过程中共晶枝晶内部首先重熔形成反常共晶,随着过冷度的增大,共晶相的形貌从蠕虫状转变为球形颗粒,被重熔形成的固相颗粒将作为剩余液相形核生长的基底,Ag-Cu共晶中共晶两相形核具有非互惠性。Co-Sn共晶合金中添加Nb元素后样品内部反常共晶形成的临界过冷度由23 K降低至15 K,而表面组织中过冷度从45 K降低至30 K。由于样品表面与坩埚壁接触有利于结晶潜热消散,反常共晶形成的临界过冷度较高。Ag-Cu共晶合金温度再辉曲线上慢速凝固阶段持续的时间较Co-Sn共晶合金要长。     

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.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.