Stress relaxation in ruby in the course of premelting anneal

V.S.Konevsky, E.V.Krivonosov, L.A.Litvinov

Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Lenin Ave., 310001 Kharkiv, Ukraine

Received December 26, 1997

Stress relaxation in ruby crystals annealed at temperatures close to that of melting (Tm) has been studied. The relaxation occurs mainly due to thermoactivated processes during first few hours of the isothermal exposure. The residual stress level depends on athermal phenomena of crystal structure defects relaxation and can be lowered somewhat by a substantial elongation of the anneal duration. As the annealing temperature is elevated from 0.95 Tm to 0.995Tm , residual stresses and their nonuniformity over the crystal length are reduced more than twice. The creep limit at 0.995Tm has been determined to amount 1.52'0.075 MPa for ruby grown by Verneuil technique.

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