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PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF MO-SI-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

Description: This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the microstructure, bend strength and compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy were studied. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The elastic limit strength of the alloy remained quite high until 1200 C with a value of 800MPa, but dropped rapidly thereafter to a value of 220 MPa at 1400 C. Results of compressive creep tests at 1200 C showed that the creep rates were quite high and varied nearly linearly with stress between 250 and 500 MPa, which suggests that diffusional mechanisms dominate the creep process. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. These results and presented and discussed.
Date: February 8, 2005
Creator: Vasudevan, Vijay K.
Partner: UNT Libraries Government Documents Department

PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF Mo-Si-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

Description: This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy at 1100 and 1200 C were studied and related to the deformation mechanisms through electron microscopy observations of microstructural changes and deformation structures. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. Results of compressive creep tests at 1200 and 1100 C showed that the creep rates were quite high at stress levels between 250 and 500 MPa, Two minima in the creep strain rate versus strain data were noted, one at small strain values and the second at much larger strains. A stress exponent of 4.26 was obtained upon plotting the strain rate corresponding to the first minima versus stress, which suggests that dislocation climb and glide dominate the creep process in the early stages. On the other hand, the large strain, minimum creep rate versus stress data gave a stress exponent of {approx}1.18, which indicates diffusional mechanisms and recrystallization dominate the later stages of the creep process. At 1100 C, a stress exponent of 2.26 was obtained, which suggests that both diffusional and dislocation mechanisms contribute to the creep strain. Based on the minimum creep rate data at 1100 C and 1200 C, the activation energy for creep was determined to be 525 kJ/mole, which is somewhat higher than that reported for self diffusion in {alpha}-Mo. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. In addition, TEM observations revealed the presence of recrystallized grains ...
Date: December 21, 2005
Creator: Vasudevan, Vijay K.
Partner: UNT Libraries Government Documents Department

EFFECTS OF LASER SHOCK PEENING ON SCC BEHAVIOR OF ALLOY 600

Description: In this study, the effects of laser shock peening (LSP) on stress corrosion cracking (SCC) behavior of Alloy 600 in tetrathionate solution were investigated. The degree of sensitization was quantified using double loop electrochemical potentiokinetic reactivation (DLEPR) tests. The sensitized Alloy 600 was demonstrated to be susceptible to intergranular SCC in tetrathionate solution. Following LSP, residual stresses and the amount of plastic strain introduced in Alloy 600 were characterized. The effects of LSP on SCC susceptibility of Alloy 600 in tetrathionate solution were evaluated by slow strain rate tests and constant load tests. Results indicate a significant increase in resistance to crack initiation and decreased susceptibility to SCC after LSP.
Date: August 1, 2013
Creator: Telang, Abhishek; Gill, Amrinder; S.R.Mannava; Vasudevan, Vijay K.; Qian, Dong & Teysseyre, Sebastien P.
Partner: UNT Libraries Government Documents Department