Internal stress superplasticity in the NiAl-Mo eutectic alloy

Internal stress superplasticity (ISS) in a NiAl-Mo based eutectic alloy was investigated by conducting thermal cycling creep tests. The alloy was anne aled at high temperatures to spheroidize the refractory metal phase. Under thermal cycling creep conditions, the alloy exhibited characteristics of IS S, that is, at low stresses, the thermal cycling creep rates were much high er than the isothermal creep rates and the corresponding stress exponent wa s close to 1. These results were compared quantitatively with the predictio ns of a theoretical model of ISS. The experimental thermal cycling creep ra tes agreed with the predicted values within an error less than one order of magnitude. Superplastic elongation of > 200% without fracture was attained during a thermal cycling tensile creep test. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.