Tribotechnical properties modification of Al-Sn alloys by ECAP
The influence of ECAP on tribotechnical properties of Al-Sn alloys was investigated. It was established that their wear rate under dry friction on steel is reduced up to 18 ± 2% after pointed treatment while the friction coefficient does not depend on the ECAP numbers.
Structure Evolution and Diffusion During Interphase Boundary Sliding in Binary Eutectics Based on Sn
Mechanical behaviour of interphase boundaries (IB) and microstructure in the binary eutectics (Al–Sn, Zn–Sn, Pb–Sn, Cd–Sn) heavily deformed by different schemes and regimes have been investigated. Experiments were carried out on the atomically clean surfaces of alloys and on the bimetallic joints with clean interfaces used as a macromodel of deformed IB. It has been shown that for the eutectics with high IB energy (Al–Sn, Zn–Sn) the interphase boundary sliding (IBS) occurs by means of the dislocation gliding, followed by a remarkable strengthening and accompanied by the formation of narrow stable IB cracks with sharp angles. For eutectics Pb–Sn and Cd–Sn with low IB energy, the IBS occurs as viscous flow and is accompanied by a correlated diffusion along IB. The softening of IB was observed. Intensity of development of the diffusion-controlled accommodation processes on IB depends on the extent of preliminary deformation and values of IB energy.
In situ strengthening of titanium with yttrium: texture analysis
In situ processing consists of heavily deforming a two-phase alloy of mutually immiscible elements to produce composite sheet or wire. In the well-studied Cu(fcc)-Nb(bcc) system, severe deformation by swaging and drawing reduces as-cast Nb filament phase thicknesses several hundred-fold after deformation. Cu-20 vol % Nb ultimate tensile strengths exceed 2000 MPa for material deformed to a true strain of η = 12, where η = ln (areaoriginal/areafinal).In an earlier study of in situ strengthening in immiscible hexagonal close-packed metals, Ti-50 vol % Y and Ti-20 vol % Y alloys were deformed by hot extrusion, hot and cold swaging. The composites were deformation processed to true strains as high as η = 7.6 to form a filamentary microstructure with filament thicknesses on the order of 0.1 μm. The deformation processing of these composites increased their ultimate tensile strengths from 318 to 945 MPa, but the specimens' original diameters were too small to allow deformation processing to the very high true strains achieved with the Cu-Nb composites.In this study, a larger casting of Ti-20 vol % Y was deformation processed to η = 12.8 in an attempt to achieve further refinement of the filament thickness. This composite formed the same filamentary microstructure up to η=7.27 observed in the earlier study of Ti-Y composites; however, at higher η values the filaments recrystallized into equiaxed grains, decreasing the ultimate tensile strength. X-ray texture analysis of the composite specimens showed a strong 〈10¯10〉 fibre texture in both the Ti and Y phases in the deformation processing range 2.25 ≤ η ≤ 7.27. This texturing is thought to constrain both the Ti and Y phases to deform by plane strain, which produces severe geometric restrictions on the ability of the plane straining filaments to achieve high η values without fracturing or recrystallizing.