Improvement of tensile ductility in 3 mol% yttria-stabilized tetragonal zirconia (3Y-TZP) by prestraining

There have been numerous investigations of the effect of material testing variables such as strain rate, temperature and grain size on the elongation to failure of superplastic ceramics. This paper presents information on the effect of rapid prestraining on superplastic ductility in a fine-grained 3 mol % yttria-stabilized tetragonal zirconia (3Y-TZP), using two testing programmes: (i) prestraining up to 130% at a prestrain rate of 1 x 10(-3) s(-1) followed by elongation to failure at a test strain rate of 1 x 10(-4) s(-1) and (ii) prestraining to 60% at prestrain rates of 1 x 10(-3) s(-1) and 2.5 x 10(-4) s(-1) followed by elongation to failure at a slower test strain rate of 1 x 10(-4) s(-1). The results showed that prestraining at the above conditions considerably improved superplastic ductility as well as reducing the time required to achieve a given elongation. The reason for this ductility enhancement is explained in terms of suppression of grain growth. (C) 1998 Chapman & Hall.