Physical-mechanical Properties of Ni-Doped Boron
G. Darsavelidze, O. Tsagareishvili, D. Gabunia, Z. Zoidze & L. Gabunia
F. Tavadze Institute of Metallurgy, Georgian Academy of Sciences, 380071, Tbilisi, Georgia

ABSTRACT: Temperature dependence of interval friction and shear mudulus of boron-nickel alloys at 1Hz torsional oscillation in the temperature range from 300 to 1000 K has been investigated. In alloys with nickel content from Ï.0 to 2.5% in the temperature range 450-500 K activation energy decreases from 1.25 to 0.8 eV and frequency factor changes from 5xlOn to lxlO12 sec'1. The origin of (he maximum is explained by twin boundary migration in (100) plane. An additional maximum has been found in alloys with nickel content > 2 5% at 650 K with activation energy equal to 1.8eV and frequency factor about 1014 sec"1. It is presumed that the variations of activation parameters of basic relaxation maximum of internal friction in nickel alloyed boron is caused by changes of electron contributions into migration activation energy of twin dislocations.

1. INTRODUCTION

In covalent crystals mobility of structural defect isdetermined to a large extent internal stresses andelectrically active alloying elements (Iendrich andHaasen, 1988). The least investigated among suchcrystals, from the point of view of dislocationdynamics, is ß-rhombohedral boron (below referred toas ß-boron). Its structure is characterized by a largenumber of deformation twins and stacking faults(McKelvy, Smith and Fynng, 1982). In complexlattice structure $-boron variations of bound length,coordination number, dimensions and shapes of latticeholes where atoms of alloying elements can beinserted are enchountered. Consequently electricalactivity of solute atoms, nature of their influence onnucleation and migration of various structural defectscan change depending on their valence and latticeposition- As certain alloying dements have a strongeffect on lattice parameters ß-boron (Lundstrom,1986), it is natural to expect ranges in crystallographicand activation characteristics of defects in alloyedboron.It has been established (Gabunia and Tsomaia,1974, Arifov, Panteleeva and Kantov, 1974) thatnickel in boron not only affects electrical and physicalproperties, but also changes the conductivity type. Inthis respect it is interesting to investigate the influenceof nickel on electrical, physical and structuralsensitive properties of ß-boron.In this paper results of reseach of electrical andphysical properties, as well as temperaturedependence of internal friction of nickel alloyed ßboronare presented. The aim of this investigation wasto find connection between changes of structuralsensitive properties of ß-boron and on concentrationand electrical activity of alloying elements.

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Physical-mechanical Properties of Ni-Doped Boron