材料期刊网

EXPLORATION OF Nb-BASED ADVANCED INTERMETALLIC MATERIALS

D M DIMIDUK(Wright-Laboratory , Materials Directorate , WL/MLLM , Wright-Patterson AFB , OH45433-7817 , USA)P R SUBRAMANIAN and M G MENDIRATTA (UES , Inc. , Dayton , OH 45432 , USA)

金属学报(英文版)

Since the late 1980's there have been a number of research efforts aimed at exploring and developing the refractory intermetalllic materials for service at temperatures which compete with the nickel-based superalloys in structural applications. These efforts have documented the physical and mechanical properties of a broad set of compositions. However, only in the last three years have these efforts yielded sufficient experimental results on single selected systems to suggest that damage tolerance, creep resistance and oxidation resistance may be obtained and controlled simultaneously. These findings led to alloy development concepts and approaches which are currently under investigation and are expected to lead to research focused on a smaller set of alloys. An overview of selected alloy development strategies and resulting structural properties is presented herein.

关键词: : refractory intermetallics , null , null

Effects of Microstructure on the Tensile, Fracture Toughness and Fatigue Behaviour of Gamma Titanium Aluminides

Young- Won (Y-W.) Kim(UES , Inc. , Materials Research Division , 4401 Dayton-Xenia Rd. , Dayton , OH 45432 , USA)(Paper presented at the International Workshop on OrderedIntermetallics 1992 , Hangzhou , China)

材料科学技术（英文）

The effects of microstructure on the deformation and fracture behaviour of two-phase TiAl alloys were investjgated under monotonic and cyclical loading conditions, over a range of temperatu res.The tensile behaviour is analyzed for deformation temperatures between RT and 950℃, Fracture resistance behaviour and toughening mechanisms at RT and 800℃ are analyzed. and the inverse relationship botween ductility and toughness is explained using the crack initiation toughness. The preliminary results of load-controlled fatigue behaviour at 800℃ are interpreted using the tensile behaviour because deformation structure and fracture modes are similar under these two loading conditions

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MICROSTRUCTURAL EVOLUTION AND CONTROL IN SUPERALLOY FORGINGS

R.Noel , D. Furrer , G. Shen and J. Lemsky(Ladish Co. , Inc. , P.O. Box 8902 , Cudahy , WI 53110-8902 , USA Manuscript received 26 Augnst 1996)

金属学报(英文版)

Optimum properties of high temperature superalloys are derived from interactions of the composition,thermomechanical deformation, and heat treatment.Nickel-base alloys contain a variety of alloying elements in a large number of combinations to produce various desired effects. The general characteristics of any specific nickelbase superalloy is determined by composition.The control of the microstructure in wrought processed superalloys can further influence the resultant component properties.The relationship between microstructure and properties is key in advanced design and manufacture of turbine engine components, and requires extensive alloy and process characterization to achieve desired results.Various forging methods have been developed and employed throughout the years to process superalloy components.Hammer forging, Press forging,and advanced isothermal press forging equipment and processes have been designed and manufactured to process speciality metals which often have very narrow processing windows.Combination processes have also been introduced into turbine engine applications,which result in a hybrid of resultant structures and properties.One such speciality,combination process is the Ladish Iso Con process which utilizes isothermal forging and conventional forging to achieve unique properties not matched by any other single process.Ladish utilizes forging presses for conventional forging, hot-die forging and for isothermal forging, in addition to hammers and ring rolling mills for wrought processing.This wide range of equipment allows flexibility in process design and optimization.Variations in temperature, strain and strain rate have been shown to significantly influence resultant grain sizes and microstructures.Tools are being developed to allow forging processes and specific forging parameters to be evaluated and optimized with regard to final microstructure before shop triale are required. Sophisticated finite element method (FEM) models are allowing the design of forging processes on computers rather than by iterative trial and error methods.

关键词: :forging , null , null

DEVELOPMENT OF INCONEL ALLOY 783, A LOW THERMAL EXPANSION, CRACK GROWTH RESISTANT SUPERALLOY

J.H.Thndermann(Inco Alloys International , Inc. , Huntington , WV 25705 , USA Manuscript received 26 August 1996)

金属学报(英文版)

Low thermal expansion superalloys have been used for a number of years in a variety of applications, including gas turbine engines. The low thermal expansion characteristics of the most widely used class of materials are derived from the ferromagnetic characteristics of Ni, Fe, and Co-based austenitic matrices containing little or no Cr.Alloy developments have been aimed at improving the oxidation resistance and stress accelerated grain boundary oxygen (SAGBO) attack.INCONEL alloy 783 is an oxidation resistant, low coefficient of thermal expansion superalloy developed for gas turbine applications. Alloy 783 represents a culmination in the development, of an alloy system with very high alumtnum content that, in addition to forming γ′,causes βaluminide phase precipitation in the austenitic matrix.This type of structure can be processed to resist both SAGBO and general oxidation,while providing low thermal expansion and useful mechanical properties up to 700℃.Key aspects of the alloy's development are presented.

关键词: :coefficient of thermal expansion , null , null , null , null , null , null , null

Alloy Design of Gamma(TiAl)Alloys

Young-Won KIM(UES , Inc. , Dayton , OH 45432 , USA)

金属学报(英文版)

Unbalanced properties for both fine-grained gamma and coarse-grained lamellar microstructures typically produced in gamma alloys are described. Efforts for the improvements are reviewed along with some experimental results. Empirical improvements have been made in cast alloys, which have led gamma alloys to a viable materials technology and to the development of various application areas for gas turbine engines as well as automotive engines. Efforts to understand fundamental and applied aspects leading to the improvements are assessed for wrought alloys. Optimization of microstructures through process control,innovative heat treatments, alloy chemistry modification and their combinations have progressed in the endeavor. Similar efforts have just begun for cast alloys where work on fundamental understanding has been lagging. Future directions are suggested for further improvements and predicted for the development of higher temperature/performance alloys.

关键词: : gamma TiAl , null , null , null

Recent Activities of the Board of Governors of Acta Materialia Inc.July 2007-July 2008

金属学报(英文版)

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Effect of pressure on thermal stability of Mg65Cu25Y10 bulk metallic glass

Scripta Materialia

The pressure effect on thermal stability of Mg65Cu2Y10 bulk metallic glass has been investigated in the pressure range up to 4 GPa. It was found that the behavior of the onset crystallization temperature versus pressure significantly differs in various pressure ranges. (C) 2003 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

关键词: metallic glass;stability;phase transformation;pressure;amorphous-alloys;crystallization;nanocrystallization;transition;liquid;phase

Applications of microdiffraction related to HREM

Microscopy Research and Technique

This paper deals with the coherent and the incoherent microdiffraction, as well as their applications, for example, determination of the nature of defects and boundaries, measurement of the strain field and identification of the symmetry, etc. The localized structure information obtained from microdiffraction has been compared with and complements that provided by HREM. (C) 1998 Wiley-Liss, Inc.

关键词: coherence of source;domain boundary;stacking fault;interference;fringe;strain field;beam electron-diffraction;strained-layer superlattices;antiphase;domain boundaries;elastic relaxation;micro-diffraction;crystals;dislocations;distortions;specimens;phase

Strengthening and improvement of sulfide stress cracking resistance in acicular ferrite pipeline steels by nano-sized carbonitrides

Scripta Materialia

Methods used to strengthen pipeline steels generally involve a reduction in their sulfide stress cracking (SSC) resistance. A non-quench ageing process is proposed to provide higher strength combined with more excellent SSC resistance for acicular ferrite (AF) pipeline steels, while microstructural characteristics are retained. (C) 2005 Acta Materiala Inc. Published by Elsevier Ltd. All rights reserved.

关键词: ageing;strengthening;sulfide stress cracking;pipeline steels

Hardness and strain rate sensitivity of nanocrystalline Cu

Scripta Materialia

The measured hardness of nanocrystalline Cu with grain sizes (( as small as 10 nm still follows the Hall-Petch relation. A rate sensitivity of 0.06 +/- 0.01 and a flow stress activation volume of 8b(3) were determined at d = 10 nm, suggesting grain boundary activities are enhanced but not yet dominant in the plastic deformation. (c) 2006 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

关键词: nanocrystalline Cu;hall-petch relation;grain size;strain rate;sensitivity;plastic-deformation;activation volume;tensile behavior;copper;metals;strength;ductility;fcc;ni;temperature