CREEP OF DUPLEX MICROSTRUCTURES

The tensile creep behavior of two ceramic composite systems exhibiting duplex microstructures was studied relative to their single-phase constituents in the temperature and stress ranges of 1100-1350 degrees C and 35-75 MPa. The equivolumetric compositions in the Al2O3:c-ZrO2 (8 mol% Y2O3) and Al2O3:Y3Al5O12 systems both exhibit lower creep rates than either of their single-phase constituents. This effect is attributed to Y3+ (and possibly Zr4+) present in the Al2O3 as a segregant which lowers the creep rate by similar to 2 orders of magnitude. It is believed that the segregation of Y3+ to the Al2O3 grain boundaries hinders the interface reaction believed to control the creep. If one of the single-phase constituents is taken to be the Y3+-doped Al2O3, the creep of the duplex microstructures can be modeled using standard composite theory applied to flow.