High-temperature air oxidation of coatings based on eutectic (β-NiAl + γ-Re) alloys and NiAl intermetallide

High-temperature air oxidation (up to 1100°C) of detonation coatings made of NiAl intermetallide and eutectic (β-NiAl + γ-Re) alloys is examined with x-ray diffraction and electron microscopy. A substantial difference between the air oxidation mechanisms of these coatings is revealed. The key factor that governs the air oxidation of these coatings is the ratio between rates at which aluminum and nickel oxides are formed. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 86–95, 2007.     

Interphase heat-and-mass transfer in a flowing bubbling layer

Results from experimental studies of heat and mass transfer for the case of cooling a steam-air mixture in a flowing bubbling layer organized in a vertical tube of different diameters are presented. Generalizing dependences for these processes are obtained.     

Stress Annealing Induced Diffuse Scattering from Ni<Subscript>3</Subscript> (Al,Si) Precipitates

Diffuse scattering caused by L₁2 type Ni₃ (Al, Si) precipitates after stress annealing of Ni-Al-Si alloys is studied. Peculiarities of diffuse scattering in the asymptotic region as compared to the Huang scattering region are discussed. Coupling between the stress annealing direction and the precipitate shape is demonstrated. Experimental reciprocal space maps (RSMs) are compared to theoretical ones. Oscillations of diffuse scattering due to Ni₃ (Al, Sc) precipitates are observed. The strengths of the precipitates are estimated from the analysis of the diffuse scattering oscillations.     

Investigation of local heat transfer associated with the evaporation of a liquid film on a horizontal ribbed tube

The heat-transfer enhancement effect of longitudinal ribs on a horizontal tube is discussed on the basis of experimental data on the local heat-transfer Co-efficients.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 6, pp. 919–924, June, 1988.     

Fusion and friction stir welding of aluminum-metal-matrix composites

Microstructure evolutions and degradations of aluminum-metal-matrix composites during fusion welding were studied and compared with thermodynamic calculations. In fusion welds of Al₂O₃-reinforced composites, the decomposition of Al₂O₃ was observed. In fusion welds of SiC whisker-reinforced composites, the decomposition of SiC to Al₄C₃+Si by reaction with molten aluminum occurred. These phenomena led to unacceptable fusion welds in aluminum metal-matrix composites. Successful welds were produced in the same composites by friction stir welding (FSW). Significant reorientation of SiC whiskers close to the boundary of the dynamically recrystallized and thermomechanically affected zone (TMAZ) was observed. The small hardening in the dynamically recrystallized region was attributed to the presence of dislocation tangles in between SiC whiskers.