Investigation of Solid-Liquid Phase Transition for Sn-54wt%In Alloy by Positron Anihilation Spectroscopy

The peak coincidence counting rate F(T) was measured for Sn-54wt%In alloy at the temperature range from room temperature to 400°C. It was observed that for both heating and cooling run, F(Τ) parameter changes . in the liquid phase. These changes were related to disintegration of SnII microcrystals. From a simple trapping model the defect disintegration enthalpy, H1,, was calculated. For heating and cooling run, the value of H1 was 0.53 ± 0.03 eV and 0.67 ± 0.07 eV, respectively. For well-annealed and cold rolled samples we find only one component, equal 200 ps, in the lifetime spectrum. PACS numbers: 64.70.Dv, 61.72.Cc, 78.70.Bj.

Positron Annihilation in Metals Defected by Action of the Tensile Force

Results of experimental investigations of uniaxially elongated mono- and polycrystalline samples of several metals (Fe, Ta, Pd, Ag, and Au), performed using the positron annihilation methods, are reviewed. The dependences of the S-parameters and positron lifetimes on the relative elongation of the samples were presented. The data obtained for polycrystalline samples indicate that in the proportionality and limited proportionality regions the changes in the physical properties are governed mainly by generation of vacancies and by kinetics of formation and transformations of vacancy clusters occurring flrst of all on the grain boundaries of monocrystallites. In the region of plastic deformati…

Positron Annihilation in Defected Monocrystalline Gold Samples

Angular distribution of the positron annihilation quanta was measured for monocrystalline gold samples, oriented in (110) and (111) directions. The samples were deformed by elongation for different deformation degrees. The S and W parameters as a function of deformation degree of the sample were determined. It was found that the dynamics of the dislocations and vacancy generation during the sliding of some crystallographic planes, depends on the crystallographic direction.

Melting Process of the Sn-45 wt.% In and Sn-77 wt.% In Alloys as Viewed by Positron Annihilation

The temperature dependences of the positron annihilation parameters F and R were determined for Sn–45 wt.% In and Sn–77 wt.% In alloys. The obtained results enabled to verify the vacancy and the quasicrystalline models of the melting process. It was found that for metals transforming into the liquid state from the structures different than the close packed structure, the melting transition are hardly explainable in terms of the vacancy model of melting. The strong trapping of positrons in metallic liquids is an indication of the presence of microvoids (vacancy clusters) or microcrystals containing defects more immense than vacancies. The share of these positron trapping centers in the volum…

Positron Annihilation in Steel Samples Deformed by Uniaxial Tension

Angular distributions of the positron annihilation quanta were measured for steel ST2 SAL samples deformed by uniaxial tension up to difierent deformation degrees. The dependences of the S parameter on the relative elongation of the samples are presented. The positron annihilation data for steel are compared with the results obtained previously for polycrystalline iron samples deformed by uniaxial tension up to difierent deformation degrees in the proportionality and limited proportionality regions.

Positron Annihilation in Solid and Liquid Bi40Sn60Alloy

Investigation of the Absorption of Annihilation Quanta in Solid and Liquid Ga and BiSn Alloy

Positron Annihilation in Polycrystalline Metals Deformed by Uniaxial Tension

Angular distributions of the positron annihilation quanta were measured for polycrystalline samples deformed by uniaxial tension up to difierent deformation degrees. The S parameter as a function of the W parameter was determined. The data obtained for samples elongated up to difierent elongation degrees indicate that in the proportionality and limited proportionality regions the changes in the physical properties of samples are governed mainly by generation of vacancies and formation and kinetics of transformations of vacancy clusters occurring flrst of all on the grains of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their…