Large tensile ductility of high purity polycrystalline yttria

It is shown that high purity polycrystalline yttria (Y2O3) exhibits a high ductility, with elongation over 40%, for temperatures between 1400 and 1550 degrees C, with strain rates from 10(-5) to 10(-4) s(-1). Deformation is accompanied by gain elongation and alignment toward the tensile axis and by a dynamic grain growth. The presence of a threshold flow stress was independently deduced from several sets of experiments, including relaxation, creep and constant strain rate tests. Accounting for the threshold stress results in an activation energy of 350 kJ/mol, a stress sensitivity exponent between 2 and 2.5 and a grain size exponent between 1.2 and 2.3.