Phase Formation Modeling of an Alloy 706 Casting Using Computational Thermodynamics
Computational thermodynamics to perform alloy and process modeling for Ni-based superalloys is a new technology which has become available to industry. This paper presents an application of the technology to a superalloy of current interest. The objective of this paper is to show how results obtained from the computational program Thermo-Calc ‘1 using a recently developed thermodynamic database for Ni-based superalloy9 can be applied to help understand solidification in INCONEL’ alloy 706. The ability of the computational method to predict both stable and metastable phase formation is explored. INCONEL@ alloy 706 was chosen because of its importance in the manufacture of large land-based gas turbine disks. In addition, the alloy’s complex structure tested the viability of the computational method. The phases examined were: Laves, MC carbide, and the y matrix. Quantitative microstructure evaluation and X-ray dispersive analysis were performed on an as-cast, vacuum induction melted (VIM) ingot. Differential Thermal Analysis (DTA) was performed on selected samples of the alloy. The experimental data was compared to the data generated via the computational approach. TM Thermo-Calc, trade name of the Division of Computational Thermodynamics, Royal Institute of Technology, Stockholm, Sweden. 8 INCONEL is a trademark of the INCO group of companies.
The microstructure of 706, a new Fe−Ni-base superalloy
Alloy 706 is a precipitation-strengthened Fe−Ni-base superalloy which has been reported to have improved machining characteristics over other similar alloys. The present work was conducted to document the phase relationships of the alloy in comparison with other Fe−Ni-base alloys. The precipitated phases identified in the alloy include γ′, Ni3Cb, Ni3Ti, M23C6, and MC. A small amount of Laves phase was also detected. The effects of some composition variations on solvus relationships for γ′ and Ni3Cb/Ni3Ti are documented. Means to take advantage of the structural response of the alloy to develop desired properties are suggested. It is shown that on the basis of chemistry and microstructural response, 706 alloy can be considered to be intermediate to the well-known alloys, 718 and 901.
Wood Microbiology: Decay and Its Prevention
Introductory text on the principles of decay and discoloration processes in wood, with emphasis on the major fungal damages which may develop during the growth, storage, and use of wood. The characteristics, detection, effects, and control of microbial attacks are stressed. Provides a synthesis of the current literature on wood microbiology, a rapidly expanding field of study. (Abstractor's note: This is an important resource for conservation researchers studying the decay of wood in art and architecture.) The following is a list of chapter headings: 1) Introduction to wood microbiology; 2) Wood deterioration agents; 3) Characteristics and classification of fungi and bacteria; 4) Factors affecting the growth and survival of fungi in wood (fungal ecology); 5) Fungal metabolism in relation to wood decay; 6) The decay setting: some structural, chemical, and moisture features of wood in relation to decay development; 7) General features, recognition, and anatomical aspects of wood decay; 8) Chemical changes in wood caused by decay fungi; 9) Ultrastructural features of wood decay; 10) Changes caused by decay fungi in the strength and physical properties of wood; 11) Colonization and microbial interactions in wood decay; 12) Decays originating in the stems of living trees; 13) Biodeterioration of stored wood and its control; 14) Wood stains and discolorations; 15) Decay problems associated with some major uses of wood products; 16) Detection of internal decay; 17) Paint mildew and related degradative problems; 18) Natural decay resistance (wood durability); 19) Chemical protection of wood (wood preservation); and 20) Some trends in wood microbiology research and a new emphasis (biotechnology). -- AATA