Pii: S1359-6462(00)00531-5

Bi2O3 is an excellent ceramic candidate for transformation-mismatch plasticity because of its low melting point, its allotropic nature and the rapid creep rate of its high-temperature d-phase. Transformation-mismatch plasticity, which has been reported in many polymorphic metals, alloys and composites [1], is a deformation mechanism taking place during a phase transformation: internal mismatch stresses produced by the coexistence of the two polymorphic phases are biased by a small externallyapplied tensile stress, thus producing a strain increment. Such compressive strain increments were indeed measured by Johnson et al. [2] for Bi2O3 subject to a single thermal excursion about the allotropic transformation under a compressive stress. For metals and alloys subjected to repeated allotropic cycling under a tensile stress, these strain increments can be accumulated up to total tensile strains well in excess of 100%, a phenomenon known as transformation superplasticity [1]. We describe in another publication [3] such tensile transformation superplasticity experiments for Bi2O3, for which a good understanding of tensile isothermal creep properties under small stresses is however first necessary. With all prior creep studies of Bi2O3 having been conducted in compression and at relatively high stresses [4,5], the purpose of the present paper is to investigate the low-stress creep behavior d-Bi2O3 in tension. Also, we investigate whether thermal cycling about the allotropic transformation under stress affects the subsequent isothermal creep properties.