INFLUENCE OF MAGNETIC-FIELD ON AMPLITUDE DEPENDENCE OF INTERNAL-FRICTION AND SHEAR MODULUS OF YTTRIUM CERAMICS BETWEEN 4.2-K AND 300-K

The amplitude dependence of internal friction and the shear modulus of yttrium ceramics of different Phase composition, density and grain si ze are studied between 4.2 and 300 K at H = 235 Oe and H = 0. Micropla sticity maxima and modulus defects are observed within the temperature ranges of structure-phase instability of the yttrium compound. Variat ions in microplasticity and shear modulus with magnetic field and resi dual fields of elastic stresses after preliminary excitation of high-a mplitude torsional vibrations (sigma = 22 MPa) in the sample are consi dered for the first time. Possible causes of microplasticity of the yt trium ceramics are discussed.