Sharif Digital Repository

Drilling super alloys with a good hole quality and acceptable surface finish is a constant challenge in modern industries dealing with such materials. Ultrasonic assisted drilling is a modern and nonconventional method of drilling which has attracted many researchers attention recently. In this study deep drilling on Inconel 738 LC is done using ultrasonic assisted drilling technique and the results are compared with those of Electro Discharge Machininng or EDM method. The results show that Ultrasonic Assisted Drilling or UAD is an appropriate alternative for EDM of Inconel. The whole process time is decrease dimensional accuracy is improved and surface roughness is decreased significantly.... 

Gamma prime (γ') precipitates are the most important phase in nickel-base superalloys that rise to a combination of desirable properties in superalloys. The morphology of these particles has important contribution to the resulting properties of superalloys. Heat treatment process of superalloys is one of the most important factors affecting the characteristics of the γ' phase. In this study, nickel-base superalloys IN738LC and GTD-111 were used to study the evolution of the microstructure and morphology of the γ' precipitates under a variety of heat treatment cycles including partial dissolution, aging for different times and under a range of cooling rates. Morphology and characteristics of... 

In this thesis, a method has been exploited to couple the atomistic domain with the coarse-grained domain. Since molecular dynamics has a high computational cost when a large number of atoms exist, coarse-grained molecular dynamics was used in which a number of atoms are assumed as a bigger bid and interatomic potential is modified for bids so that the material’s mechanical properties remain constant. This method not only reduces the computational cost of calculating forces in molecular dynamics simulation but also, the time step used in Coarse-Grained Methods can be more than atomistic simulations as the frequency of occurring phenomena in CG scale is less than atomistic scale.The advantage...