U. Krämer

THE ELECTROPLASTIC EFFECT IN V3Si

The present experimental work undertook to reveal the existence of the EPE at high homologous temperature (0.60 to 0.85) in the)superconducting intermetallic compound V3SI (A-15 or ~-W type of structure . In this paper results of the secondary creep deformation for several chemical compositions within the range of homogeneity are presented. The results attained are compared with the results of investigations of macroscopic deformation in V3Si performed under static conditions (11,15). So, the magnitude of EPE in V3Si is determined. Results of creep curves with d.c. and alternating current (s.c.) heating are submitted. The analysis of TEM work and etch experiments after deformation are underway. Superconducting properties before and after deformation were reported elsewhere (12).

Creep deformation of V3Si single crystals

From the experiments during steady state creep of V3Si single crystals at T=1280 to 1400° C and σ=1 to 7×107 Pa, activation volumes, 10 to 70 b3, and activation enthalpies, 2 to 11 eV, have been derived. With deviation from stoichiometric composition a hardening effect has been experimentally established. It is suggested that the rate controlling process was due to dislocation glide and dynamic recovery by dislocation climb.

High-temperature creep and structure investigation of nearly stoichiometric Fe3Si: Part 1 Creep behaviour of Fe-Si single crystals

Single crystals of nearly stoichiometric Fe3Si were creep-deformed at temperatureT = 450 to 850° C and applied stressσ=40 to 250 MPa. While the temperature dependence of the steady-state creep rate of crystals with less than 25 at% Si can be described by an exponential function exp (−ΔHexp/kT), the Fe-26 at% Si samples show an exponential dependence only below 500° C and above 600° C. At intermediate temperatures the dependence is weak. It is suggested that in this intermediate range two phases exist. The experimental results are consistent with the assumption that the phase boundaries do not hinder dislocation movement, and that the disocation velocity in the two phases is different.

High-temperature creep and structure investigation of nearly stoichiometric Fe3Si

X-ray diffraction measurements were carried out on powdered single crystals of nearly stoichiometric Fe3Si. The experimental data obtained in the temperature range from room temperature up to 750‡ C in terms of long-range order, thermal expansion, phase transition and Debye temperature (together with values of the Curie temperature) support the existence of two modifications of the DO3 structure for Fe-26 at% Si alloys and a phase transition in the DO3 structure field at 595‡ C. The high-temperature modification has a smaller thermal expansion coefficient, a higher Curie temperature and a higher Debye temperature.