材料期刊网

A STUDY OF CARBIDE GROWTH IN MAR-M247 LC ALLOY BY DIRECTIONAL SOLIDIFICATION METHOD

J.H Lee , J. Chen , S.J. Choe , Y.T. Lee and H.M. Kim(High Temperature Materials Laboratory , Korea Institute of Machinery & Materials , 66 Sangnam Dong , Changwon , Kyungnam , 641010 , Korea Manuscript received 26 August 1996)

金属学报(英文版)

The carbide growth behavior of MAR-M247 LC alloy was investigated by directional solidification and quench method. The carbide volume fraction, trapping and growth behavior were correlated with the growth rate.It was found that the carbide volume fraction decreased at slower growth rate.This decreasing was caused by lower solidliquid interface trapping ability at slower growth rate.

关键词: :carbide , null , null , null

FUTURE OF HIGH TEMPERATURE MATERIALS FOR GAS TURBINE

C.X. Shi(National Natural Science Foundation of China , Beijing 100083 , China Manuscript received 26 August 1996)

金属学报(英文版)

A comprehensive survey was made of various candidate high temperature materials for gas turbine use, and their relative merits and drawbacks were assessed. It is shown that superalloys, fine-tuned, will be persistent for the next few decades, to be followed up by high temperature intermetallics. For advanced ceramics, the problems of reliability and cost will have to be solved before they can be used in critical parts of engines.So are C/C composites with their oxidation problem. Surface modification and development of thermal barrier coatings can effectively overcome many problems of gas turbine materials and these technologies should be emphasized.

关键词: :superalloy , null , null , null , null

RESEARCH AND DEVELOPMENT OF HIGH TEMPERATURE STRUCTURAL MATERIALS FOR AERO-ENGINE APPLICATIONS

G.Q. Zhang

金属学报(英文版)

The status of research, development of superalloys and materials processing & fabrication technologies for aero-engine applications in China Aviation Industry, with an emphasis on recent achievements at BIAM including directionally solidified and single crystal superalloys for blade and vane applications, wrought superalloys for aero-engine disks and rings, and powder metallurgy (PM) superalloys for high performance disk applications were described. It was also reviewed the development of new class of high temperature structural materials, such as structural intermetallics, and advanced material processing technologies including rapid solidification, spray forming and so on. The trends of research and development of the above mentioned superalloys and processing technologies are outlined. Cast, wrought and PM superalloys are the workhorse materials for the hot section of current aero-engines. New high temperature materials and advanced processing technologies have been and will be the subject of study. It is speculated that high performance, high purity and low cost superalloys and technologies will play key roles in aero-engines.

关键词: superalloy , null , null

High Temperature Oxidation as a Production Route for Electronic Materials

W.GAOZ.W.LI

中国腐蚀与防护学报

Oxidation of metallic components often results in degradation and structural failure, prevention is therefore an important topic. On the other hand, oxidation process creates new products such as metal oxides, can be used as a production route. A well-known process in semiconductor industry is that oxidation in dry or wet atmosphere is a popular way for growth of multi-functional SiO₂ films on Si wafers. Recently, oxidation processes under controlled conditions (atmosphere, temperature, and time) are used to prepare various oxides, carbides, or nitrides with micro-/nano-structures, well-defined composition, dimension, shape and properties. The use of oxidation now includes thin film and nano-/micro-sized devices, and porous oxides for sensing and catalysis purposes. This paper introduces the research activities in the authors' group on applications of oxidation as a tool for synthesis of functional materials.

关键词: oxidation , null , null , null

Recent Achievements in Developing Low Temperature and High Strain Rate Superplastic Materials

J.C Huang

材料科学技术（英文）

This paper is to briefly outline our recent activities in developing low temperature or high strain rate superplastic materials, including aircraft-used and general-purpose Al- and Mg-base alloys or composites, as well as Ti3AI base intermetallic alloys. The processing routes applied included the thermomechanical treatment, equal channel angular pressing and other extrusion or forging methods.

关键词:

Predicting remnant lifetime of high-temperature materials by a resistance degradation model

Materials at High Temperatures

Lifetime and remnant life of engineering materials at high temperature has been analyzed based on a resistance degradation model. It can be demonstrated that the lifetime includes two time processes: resistance degradation process before crack initiation and crack growth process after the crack initiation. Traditional lifetime prediction, via the crack growth model, was found to involve the paradox that the lifetime is in proportion to the initial crack size. Whereas, experiments of static fatigue using glass sheet specimens did not confirm this proportional relationship. For a smooth sample, fracture resistance depends on the strength of the material, so a strength degradation model was used to estimate the lifetime zone between an upper and lower bound. It is defined that the material fails when the residual strength decline to the working stress or deformation reaches a designed limit. It is concluded that the quantity of lifetime mainly depends on the rate of resistance degradation for a brittle component under applied load. Thus, lifetime prediction is simulated as a simple relationship between distance, rate and time, in which the distance is known, the rate can be obtained from experiments and then the lifetime can be calculated.

关键词: remnant lifetime;a resistance degradation model

THE MECHANICAL BEHAVIOR OF LABORATORY CROSS-WELD SPECIMEN AND ITS RELATION WITH THE PRACTICAL CASES AT ELEVATED TEMPERATURE

Author S.T. TU , J.M. Gong and X. Ling Nanjing University of Chemical Technology , Nanjing 210009 , ChinaManuscript received 18 October 1998

金属学报(英文版)

In order to interpret the test results of crossweld specimens for application in practical welded components, the present paper studies the high temperature behavior of laboratory cross weld specimens in terms of the uniaxial material tests and numerical simulations. It is found that the crossweld specimen may be used for the high temperature strength assessment, but can hardly be used for life assessment of the practical welded components, which depends on the loading conditions of the components.

关键词: high temperature , null , null , null , null

THE INVESTIGATION OF KINETICS OF HIGH-TEMPERATURE STRUCTURE TRANSFORMATION OF HOMOPHASES AND HETEROPHASES MATERIALS

M.D. Starostenkov , E. V.Kozlov , O. V. Andruhova , N. V. Lomskikh , N.M. Gurova and A. V. Borissov 1) General Physics Department , ASTU , Lenin St. 46 , Barnaul , 656099 , Russia 2) Physics Department , TSABU , Solyanaya Sq. , 2 , Tomsk , 634003 , Russia

金属学报(英文版)

The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.

关键词: computer simulation , null , null , null , null

High Temperature Oxidation of FGH96 P/M Superalloy

F.J. Liu , M.C. Zhang , J.X. Dong , Y.W. Zhang

金属学报(英文版)

High temperature oxidation behaviors of FGH96 P / M superalloy have been studied in air at temperatures ranging from 600 to 1000℃. By means of isothermal oxidation testing, X-ray diffraction, SEM (scanning electron microscopy) and EDS (energy dispersive X-ray spectroscopy) analyses, the oxidation kinetics as well as the composition and morphology of scales were investigated. Thermodynamic calculations were used to explain the oxidation mechanism. The results showed that as the oxidation temperature increased, the oxidation rate, the scale thickness and scale spallation increased. FGH96 P / M superalloy exhibits good oxidation resistance at temperature below 800℃. The oxidation kinetics follows an approximately parabolic rate law, and the oxide layer was mainly composed of Cr2O3, TiO2, and a little amount of NiCr2O4. The oxidation is controlled by the transmission of chromium, titanium, and oxygen through the oxide scale.

关键词: FGH96 P/M superalloy , null , null

High temperature deformation and microstructural evolution of Mg-Gd-Y alloys

Materials Science and Technology

The high temperature deformation behaviours of Mg-10Gd-3Y (GW103) alloys processed by extrusion and extrusion followed by equal channel angular extrusion (ECAE) were investigated and compared, and the maximum tensile elongations of 390 and 490% were obtained in the two specimens respectively. The different processing routes led to different microstructural features, and the extrusion followed by ECAE (EX-ECAE) specimens usually showed higher elongations than as extruded ones under the same deformation conditions. The deformation mechanisms of GW103 alloys were analysed in terms of the strain rate sensitivity exponent, microstructural evolution and activation energy. The high elongations of as extruded specimens were attributed to the combined effects of dynamic recrystallisation and grain boundary sliding, which was accompanied by lattice diffusion. However, grain boundary sliding controlled by the combination of grain boundary and lattice diffusions was dominant in the EX-ECAE specimens.

关键词: Mg-Gd-Y alloy;Equal channel angular extrusion;High temperature;deformation;Recrystallisation;Microstructure;strain-rate superplasticity;severe plastic-deformation;az61 magnesium;alloy;grain-size;extrusion;zk60;behavior;metals;ecap;flow