晶粒细化对Cu—20Ni—20Cr合金氧化行为的影响

为探讨晶粒尺寸变化对三元复相合金氧化行为的影响，采用机械合金化制备了纳米晶三元Cu-20Ni-20Cr合金，并对比研究了该合金与同成分的铸态合金在700℃～800℃，0．1MPa纯氧气中的氧化行为。结果表明，铸态合金表面没有形成连续的Cr2O，保护膜，而是形成了含有所有组元氧化物及它们复合氧化物的复杂氧化膜结构。纳米晶Cu—20Ni—20Cr合金在700℃时合金表面形成了连续的Cr2O3氧化膜，而800℃时虽没有形成Cr2O3外氧化膜，但氧化膜规则平坦，外层是CuO，中间层是Cu2O，NiO和Cr2O3组成的混合氧化物区，内层则形成了一薄但不连续的Cr2O3层。晶粒细化降低了合金表面形成Cr2O3氧化膜所需活泼组元Cr的临界浓度。     

晶粒细化对Cr-25Nb合金高温氧化行为的影响

采用电弧熔铸和机械合金化+热压烧结技术制备晶粒尺寸相差较大的Cr-25Nb合金,研究其在950及1200 ℃空气中的氧化行为。结果表明,熔铸态及机械合金化Cr-25Nb合金氧化后均没有发生Cr的单一外氧化,而形成了以Cr2O3为外层、NbCrO4为内层的双层氧化膜结构;机械合金化Cr-25Nb合金在950及1200 ℃的氧化速度均小于熔铸态合金,特别是在1200 ℃氧化100 h后,熔铸态Cr-25Nb合金的氧化增重是机械合金化合金的2倍多。这主要是因为晶粒细化促进了氧化膜内应力的释放,提高了氧化膜与基体的粘附性     

机械合金化Ni-20Cr合金的循环氧化行为

结合XRD、TEM、SEM、OM等表面分析技术,研究机械合金化Ni-20Cr合金在1000℃空气中的循环氧化行为,并与熔炼合金进行比较.结果表明:200 h循环氧化后,机械合金化Ni-20Cr合金表面生成Cr2O3氧化膜,且剥落轻微;而熔炼Ni-20Cr合金表面生成由NiO和NiCr2O4组成的氧化膜,且剥落严重,其单位面积失重明显大于机械合金化Ni-20Cr合金.在实验条件下,机械合金化Ni-20Cr合金较熔炼Ni-20Cr合金具有更好地抗循环氧化性能.一方面,晶粒细化促进保护性Cr2O3膜的生成;另一方面,晶粒细化使氧化膜中的热应力减小并可通过扩散蠕变来释放,使氧化膜的粘附性明显提高.     

晶粒细化对Fe-Cr、Ni-Cr合金氧化行为的影响

采用机械合金化法制备块体纳米晶Fe-20Cr、Ni-20Cr合金,并研究其在1000℃空气中的氧化行为.结果表明：由于晶粒细化,加快了Cr向合金表面的扩散速度,增加了活泼组元Cr氧化物的形核位置,降低了Fe-Cr、Ni-Cr合金形成单一连续Cr2O3氧化膜所需的临界Cr浓度,故机械合金化Fe-20Cr、Ni-20Cr合金氧化后形成了单一的Cr2O3外氧化膜,且氧化速率明显小于普通晶粒大小的熔炼Fe-20Cr、Ni-20Cr合金.      

不同方法制备的Cu-Cr合金的氧化行为

采用粉末冶金（PM）、机械合金化（MA）及磁控溅射（MS）方法制备了具有不同显微组织的二元双相Cu-Cr合金（PM Cu-25Cr,MA Cu-20Cr和MS Cu-20Cr)。结果表明：经700℃，0.1MPa纯氧气氧化后，PM Cu-25Cr合金形成了包含CuO,Cu2O,Cr2O3及CuCr2O4的复杂混合氧化膜，氧化增重最大；MA Cu-20Cr合金在混合的氧化膜下出现了连续的Cr2O3层，氧化增重次之；MS Cu-20Cr合金涂层则形成了简单CuO与Cr2O3的两层膜结构，氧化增重最小。氧化行为的差异与合金显微组织的细化程度有密切关系。     

二元双相Cu-50Cr合金在700─900℃空气中的氧化

Cu－50Cr合金在700—900℃空气中的氧化结果表明,合金的氧化动力学在700和800℃遵循抛物线速度规律,在900℃其瞬时抛物线速率常数随时间而降低．合金氧化外层膜是CuO和Cu2O,内层膜由氧化铜和尖晶石型氧化物为基并嵌有Cr颗粒组成,Cr表面有Cr2O3和Cu2Cr2O4膜。900℃的氧化膜与基体金属界面上可观察到连续的Cr2O3层.合金未形成Cr的选择性外氧化．     

显微组织对Ni-Cr合金热腐蚀行为的影响

采用机械合金化法和真空熔炼法制备了不同显微组织的Ni-20Cr（质量分数，％，下同）合金，并研究其在950℃，75％Na2SO4＋25％K2SO4（质量分数，下同）盐膜下的热腐蚀行为。结果表明：细晶的机械合金化Ni-20Cr合金热腐蚀后表面形成了单一连续的Cr2O3外氧化膜，有效地阻止了硫的向内扩散，延长了热腐蚀过程的孕育期，呈现出较普通晶粒尺寸的熔炼Ni-20Cr合金更好的抗热腐蚀性能。     

三相Cu—Ni—30Cr合金高温氧化行为研究

研究了Cr含量相对较高的Cu—Ni—30Cr合金在700℃-800℃，0．1MPa纯氧气中的氧化行为。结果表明：合金氧化动力学较复杂，其瞬时抛物线速率常数随时间而降低，氧化动力学曲线通常不是由单一的抛物线或直线组成而是由几段组成。Cu—Ni—Cr为三相合金，3相的存在增加了合金表面形成Cr2O3氧化膜所需临界浓度，但30at％Cr足以使合金表面形成连续的Cr2O3外氧化膜。氧化膜内层是合金和氧化物相共存的混合区，被氧化的岛状物是由Cr2O3和Cu，Ni组成。这种混合内氧化机制与经典内氧化明显不同。     

Cu-30Ni-20Cr纳米复合镀层的高温氧化行为

采用复合电沉积法制备出新型的Cu-30Ni-20Cr纳米复合镀层．该镀层的组织结构与常规Cu-Ni-Cr三元合金不同，是由Cu-Ni基固溶体（晶粒尺寸约为60nm）和纳米Cr颗粒（平均尺寸约为28nm）组成．与相同工艺条件下制备的Cu-40Ni合金镀层相比，Cu-30Ni-20Cr纳米复合镀层在800℃空气中的氧化速率显著降低，这是由于它能迅速形成一层连续、致密的Cr2O3膜所致．对Cr颗粒在Cu-30Ni-20Cr纳米复合镀层的高温氧化过程中所起的作用进行了讨论．     

机械合金化对热压合成Laves相NbCr2合金1100 ℃氧化行为的影响

采用机械合金化+热压烧结工艺制备Laves相NbCr2合金,研究球磨时间对热压合金晶粒尺寸及致密度的影响,探讨了晶粒细化对其1100 ℃氧化行为影响的作用机制.结果表明,随着Cr-Nb粉末球磨时间的延长,热压合金组织越来越致密,晶粒尺寸越来越小.当球磨时间达到100 h时,NbCr2合金的相对致密度及晶粒尺寸分别达到98.7%和35 nm.晶粒的细化有利于Cr原子扩散能力的提高,促进了Cr2O3膜的形成;但晶粒过细时,导致氧化膜内生长应力的增加,引起氧化膜的开裂、脱落,从而加剧了氧化.     

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.