N. I. Noskova

Effect of severe plastic deformation on the microstructure and tribological properties of a babbit B83

The effect of severe plastic deformation carried out at room temperature by the methods of equal-channel angular (ECA) pressing and surface friction treatment (SFT) on the microstructure, rate of wear, and friction coefficient of a babbit B83 (11.5% Sb, 5.5% Cu, Sn for balance) has been investigated. It has been shown that severe plastic deformation that leads to a drop in the grain size of the babbit to 100–300 nm and to a strong refinement of particles of intermetallic phases (SnSb, Cu3Sn) causes a considerable (twofold-fourfold) reduction in the rate of wear and a decrease in the friction coefficient of a steel-babbit pair under test conditions with lubrication at small (0.07 m/s) and enhanced (4.5 m/s) sliding velocities. As was shown by structural investigations performed with the use of scanning electron microscopy, this positive influence of severe plastic deformation on the tribological properties of the babbit is connected with the formation on the deformed-babbit surface of a developed porosity, which improves conditions for lubrication of the babbit-steel friction pair due to the action of the self-lubrication effect and thereby favors the retention of a stable regime of boundary friction of this pair. The formation of porosity is a result of the accelerated spalling of hard brittle intermetallic particles of SnSb and Cu3Sn from the friction surface of the deformed babbit, which is caused by weakening and loss of the bonding of these particles with the plastic matrix (α solid solution based on tin) in the course of severe plastic deformation of the babbit. At the same time, under the conditions of dry sliding friction of the babbit-steel 45 pair, when a fatigue mechanism of wear of the alloy under consideration predominantly develops, this plastic deformation yields an approximately 1.6-fold increase in the rate of wear of the babbit. This increase is mainly due to numerous defects (microcracks) that are introduced into the babbit structure upon its severe plastic deformation and reduce the resistance of the surface layer of this material to the fatigue mechanism of wear.

The structure and properties of nanocrystalline polyphase alloys

Abstract The phase composition and microstructure of Fe73,5Cu1Nb3Si13,5B9, Fe73Ni0,5Cu1Nb3Si13,5B9, Fe5Co70Si15B10, Pd81Cu7Si12 and Pd77,5Cu6Si16,5 obtained in a nanocrystalline state by crystallisation of the initially amorphous alloy were studied using electron microscopy. Ribbon samples of Fe73,5Cu1Nb3Si13,5B9, Fe73Ni0,5Cu1Nb3Si13,5B9, Fe5Co70Si15B10, Pd81Cu7Si12 and Pd77,5Cu6Si16,5 alloys obtained by rapid quenching and annealing were tested for strength and plasticity under conditions of high-rate stretching and for creep behaviour (at 773–823 K). The temperature variation of strength and plasticity was studied. Validity of the Hall-Petch relation for the above alloys in the nanocrystalline state was verified.

Effect of rapid crystallizations on the properties of Fe5Co70Si15B10

Abstract The phase composition and microstructure of Fe5Co70Si15B10 obtained in a nanocrystalline state by crystallization of the initially amorphous alloy were studied using electron microscopy. We applied the crystallization at 923K for 10 s to refine the grains in the alloy and to compare its magnetic and mechanical properties with those of the alloy crystallized by the conventional procedure. Rapid crystallization of a metallic glass at an elevated temperature under rapid heating and cooling was shown to result in significant gain in the coercive force, remanent magnetization, microhardness and strength.

Structure of nanocrystalline Cu subjected to ultrasonic waves

Abstract Structure and properties of nanocrystalline Cu treated by focused ultrasonic waves were studied. It was found that this treatment produces microscopic deformation processes and redistribution of internal stresses in grains.

Structure transformations in amorphous Fe,Co, and Pd based alloys during crystallization to the nanocrystalline state

Abstract Amorphous Fe73.5Cu1Nb3Si13.5B9, Fe5Co70Si15B10 and Pd81Cu7Si12 alloys, produced by superfast quenching from the melt followed by fast heating to 723–923 K and soaking for 10 s in vacuum were investigated. The crystallization of an amorphous Fe73Ni0.5Cu1Nb3Si13.5B9 alloy was determined by methods of transmission electron microscopy (in situ). The Fe73.5Cu1Nb3Si13.5B9 alloy annealed at 923 K for 10 s produces a grain size of 6 nm, with phases α-FeSi13 at.%, (FeNb)2B, and (FeNb)B. An Fe5Co70Si15B10 alloy annealed at 923 K for 10 s produces a grain size of 25 nm, with phases - α-Fe, α-Co, β-Co, Fe3Si, Co2Si, and (FeCo)2B. A Pd81Cu7Si12 alloy annealed at 823 K for 10 s produces a grain size of 25 nm, with phases - Pd, Pd-Cu(γ), Pd5Si, i-PdxSi.

Structure and microhardness of nanocrystalline composite alloys on the basis of Al and Ti

A nanotechnology for production of layered composite nanocrystalline Al-Si, Al(1Hf + 0.2Nb + 0.2Sn, wt %)-Si, Al(0.5Ce + 0.5Re + 0.1Zr, wt %)-Si, and Ti-Si alloys has been suggested. The structure of the nanocrystalline composites obtained has been studied by the methods of optical microscopy and scanning and transmission electron microscopy. Experimental data on the microhardness of layered composite nanocrystalline alloys on the basis of aluminum and titanium are given. The microhardness of the nanocrystalline two-layered Al-Si composite in comparison with submicrocrystalline aluminum increased by a factor of three. In the nanocrystalline two-layered Ti-Si composite (compacted from powders), the microhardness also increased by a factor of almost six in comparison with nanocrystalline titanium. In the nanocrystalline two-layered composite alloys of aluminum, the increase in microhardness in the case of the Al(Hf,Nb,Sn)-Si alloy was up to 45% as compared to the composite on the basis of the metallic foil and by a factor of two as compared to the powder-compact composite; and in the case of the Al(Ce, Re,Zr)-Si alloy, by a factor of 1.6 and 2.7, respectively. An increase in the number of layers in the composites had no significant effect on the level of microhardness.

Magnetic anisotropy induced by stress annealing, its thermal stability, and structure of the Fe5Co72Si15B8 alloy

The efficiency of the magnetic-anisotropy induction in the Fe5Co72Si15B8 amorphous alloy during its thermomechanical treatment and the thermal stability of the anisotropy are shown to depend on the structural state of the alloy. Structural inhomogeneities (microinhomogeneities and preprecipitates) formed in the structure of the amorphous alloy upon annealing at 350–430°C increase both the efficiency of the magnetic-anisotropy induction in the course of subsequent heat treatment at 290°C combined with tensile deformation and the thermal stability of the anisotropy.