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misfit-dislocation
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An Investigation of Alloying Elements Effect on Creep Behavior of Ni-Based Super Alloys Using Molecular Dynamics
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The aim of this study is to investigate the role of the temperature, stress, strain rate, and rhenium (Re) on the γ\/γ^' interfacial misfit dislocation network and mechanical response of Ni-based single crystal superalloys. The interfacial network plays an important role in the superior creep behavior of Ni-based superalloys. Therefore, a comprehensive understanding of this topic would help us to go through the impact of various factors on the mechanical and creep properties at high temperatures to achieve an optimal design. Due to the mismatch between the two phases, a dislocation network forms after aging at high temperatures to alleviate the stress field. The (100), (110), and (111)...
On phase transformations in a Ni-based superalloy
, Article Philosophical Magazine ; Volume 93, Issue 10-12 , Mar , 2013 , Pages 1351-1370 ; 14786435 (ISSN) ; Sharghi Moshtaghin, R ; Sadeghahmadi, M ; Pirouz, P ; Sharif University of Technology
2013
Abstract
In this study, a particular nickel-based superalloy has been studied by transmission electron microscopy and the results are discussed in terms of phase transformations that may have taken place. The alloy has been found to consist of three major phases; a FCC γ phase containing a random distribution of nearly spherical γ′ - Ni3Al(Ti) - precipitates and elongated thin Ni3Ti(Ta) platelets with a hexagonal structure. The orientation relationships between the different phases have been determined; loss of coherency and possible occurrence of misfit-relieving interfacial dislocations are discussed and compared with experimental observations, and possible mechanisms of phase transformations are...
Interface effect on the formation of a dipole of screw misfit dislocations in an embedded nanowire with uniform shear eigenstrain field
, Article European Journal of Mechanics, A/Solids ; Volume 51 , May–June , 2015 , Pages 154-159 ; 09977538 (ISSN) ; Enzevaee, C ; Gutkin, M. Y ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
The critical condition for the generation of a screw misfit dislocation dipole (MDD) at the interface between a nanowire (NW) with uniform shear misfit strain and its surrounding unbounded matrix within surface/interface elasticity theory is of particular interest. The analysis is carried out using the complex potential variable method. It is shown that the critical radius of the NW corresponding to the onset of the MDD generation decreases with the increase in the uniform shear eigenstrain inside the NW as well as when the stiffness of the NW increases with respect to the matrix. The critical radius strongly depends on the non-classical interface parameter. Comparison is made with classical...
Mechanical properties of uncoated and aluminide-coated rené 80
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1 , 2010 , Pages 125-137 ; 10735623 (ISSN) ; Nategh, S ; Sharif University of Technology
Abstract
Nickel-base superalloys such as René 80 are widely used in manufacturing aircraft turbine blades. They are usually coated in order to increase their wear, oxidation, erosion, and hot corrosion properties against environmental degradation. In this article, the mechanical behavior (tensile and low-cycle fatigue (LCF)) of uncoated and aluminide-coated (CODEP-B) René 80 has been studied at 871 °C and 982 °C. Experimental results show that the tensile properties of coated specimens are relatively lower than those of uncoated ones in the same conditions, but application of coating increases the LCF life of René 80 at T = 871 °C, 982 °C, R = (εmin/εmax) = 0, strain rate of 2 × 10-3 s-1, and Δεt =...
Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers
, Article Materials Letters ; Volume 65, Issue 3 , February , 2011 , Pages 523-526 ; 0167577X (ISSN) ; Simchi, A ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
Abstract
Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the...