Effects of alloying iron with nickel on edge dislocation motion resistance

Studies of microplastic strain in-Fe and in Fe-Ni solid solution have provided data on the concentration and temperature dependence of the edge-dislocation motion resistance arising from elastic interaction with alloying-element atoms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 89–93, March, 1984.     

Quantum many-body culling: production of a definite number of ground-state atoms in a bose-einstein condensate

We propose a method to produce a definite number of ground-state atoms by adiabatic reduction of the depth of a potential well that confines a degenerate Bose gas with repulsive interactions. Using a variety of methods, we map out the maximum number of particles that can be supported by the well as a function of the well depth and interaction strength, covering the limiting case of a Tonks gas as well as the mean-field regime. We also estimate the time scales for adiabaticity and discuss the recent observation of atomic number squeezing [Chuu, Phys. Rev. Lett. 95, 260403 (2005)10.1103/PhysRevLett.95.260403].     

Grain-boundary hardening in polycrystalline copper-based solid solutions

A study is made of the contribution of grain-boundary hardening to the overall hardening in a polycrystalline material on the basis of Ashby's model. Yield curves are used for copper-based solid solutions in polycrystalline and singlecrystal forms. It is shown that the contribution from statistically accumulated dislocations to the yield stress in a polycrystalline specimen reflects the behavior of the corresponding single crystal. The contribution from grain boundaries to the yield stress can be described in terms of the additional dislocation density due to the joint grain deformation in the aggregate up to high strains. At low strains, the main role in hardening of a polycrystalline material is played by the grain boundaries. This extends up to larger strains as the strain temperature is reduced and the alloy-element concentration increases.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 47–52, January, 1984.     

Test of calculations on dislocation blocking in copperbase solid solutions

The creep threshold =f(c) for deformation aging under load is examined for Cu-Al, Cu-Ge, and Cu-Ni solid solutions; in each case it is in good general agreement with the theoretical relation for dislocation blocking. The data provide support for theoretical calculations on the main dislocation-blocking factors.     

Microplastic deformation of polycrystals during cyclic loading

A model of microplastic deformation of polycrystals during zero-start cyclic loading with tensions lower than the yield strength is proposed according to which during cycling, thermally activated movement of dislocations occurs under conditions of stress relaxation. Based on this model and the statistical theory of polycrystalline microdeformation, the accumulation of microplastic deformation is theoretically described as a function of the number of loading cycles and the stress amplitudes. It is theoretically proved that in the cycling process the microplastic deformation that accumulates over one cycle decreases as the number of cycles increases; up to the macroscopic elastic limit it is independent of the stress amplitude, and then sharply increases. Agreement of the theory with experimental data for spring alloys is observed in the density of mobile dislocations, which decreases during cycling.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 29–34, March, 1990.