Creep of Duplex Microstructures

Abstract

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°C and 35–75 MPa. The equivolumetric compositions in the Al 2 O 3 : c –ZrO 2 (8 mol% Y 2 O 3 ) and Al 2 O 3 :Y 3 Al 5 O 12 systems both exhibit lower creep rates than either of their single‐phase constituents. This effect is attributed to Y 3+ (and possibly Zr 4+ ) present in the A1 2 O 3 as a segregant which lowers the creep rate by ∼2 orders of magnitude. It is believed that the segregation of Y 3+ to the A1 2 O 3 grain boundaries hinders the interface reaction believed to control the creep. If one of the single‐phase constituents is taken to be the Y 3+ ‐doped Al 2 O 3 , the creep of the duplex microstructures can be modeled using standard composite theory applied to flow.