Alex Berner

Atomistic study of interaction zone at copper-carbon interfaces

Abstract Formation of Cu–C composite is a difficult technological problem: carbon is practically insoluble in copper. We show that the heat treatment of the Cu–C composite leads to the formation of thin (approximately 50 nm) interface, which provides the bonding between fiber and matrix. The high-resolution scanning electron microscopy (HR SEM) study displays the formation of the interaction zone. Monte Carlo simulations with repulsive Cu–C interatomic potentials study this zone on the interface.

GRAIN BOUNDARY GROOVING WITH SIMULTANEOUS GRAIN BOUNDARY SLIDING IN Ni-RICH NiAl

Abstract Thermal grooving at grain boundaries in Ni-rich NiAl was studied by atomic force microscopy technique. The determined average ratio of grain boundary to surface energy for large-angle grain boundaries at 1400°C is 0.45, which is in a good agreement with the results of computer simulations. It has been found that in most cases thermal grooving at the grain boundaries is accompanied by relative shift of the adjacent grains. This shift is associated with the grain boundary sliding caused by the relaxation of internal substructure of the specimen. A model of grain boundary grooving with the simultaneous sliding is developed. The calculated grain boundary groove profiles are in a good agreement with the experimentally measured ones.

The origin of a new phase observed during quenching of a TiAl-2Fe alloy

Abstract Microstructure formation in the Ti–49.6at.% Al–1.9at.% Fe alloy after fast and slow cooling from 1200°C was examined and analyzed by X-ray diffraction, scanning and transmission electron microscopy combined with electron probe microanalysis. Formation of a previously unidentified τ′2 phase is reported and discussed. It has a tetragonal lattice with lattice parameters a=11.5 A, c=13.8 A. Possible orientation relationships between the τ′2 phase and the parent FeTi(Al) are [010]τ′2 ∣∣ [001]FeTi(Al) [100]τ′2 ∣∣ [110]FeTi(Al) and [001]τ′2 ∣∣ [ 1 10]FeTi(Al).

Structure and mechanical property variations in Mg–Gd–Y–Zn–Zr alloy depending on its composition and processing conditions

Abstract An effect of alloying element content on mechanical properties and precipitate formation in Mg–RE alloys was studied for Mg–8Gd–4Y–1Zn–0.4Zr (wt%) and Mg–10Gd–5Y–1.8Zn–0.4Zr (wt%). It is shown that small variations in the alloying element concentration can be used to manipulate the alloy microstructure and precipitate formation towards eliminating the asymmetry (tension/compression) and anisotropy of yield stress.

Distribution of elements in the surface layer of amorphous AlLaNi ribbons

Abstract Amorphous ribbons of Al91La5Ni4 were produced by melt spinning. Ribbons 3 mm wide and 20 μm thick were obtained by rapid quenching of the melt in vacuo from 1273 K onto a Cu drum surface. The depth distribution of the elements in the surface layer of the specimen was studied by Auger electron spectroscopu combined with ion sputtering, and by electron probe microanalysis through varying the energy of the primary electrons. It was shown that the La and Ni contents of a surface layer several hundreds of nanometers thick are considerably lower than those in the bulk. La and Ni depletion was discovered on both faces (contacting and free) of the amorphous ribbons. The data obtained were explained on the basis of the concept of different surface activities of alloy components in the liquid state. In the process of melt spinning, a new surface is formed and the components in the near-surface layer are redistributed. As a result of the extremely limited duration of the quenching, there is insufficient time for the redistribution of the elements in the solid state. Therefore, the observed component depth distribution is the result of the “freezing” of the liquid-state near-surface layer.