Physically motivated model for creep of directionally solidified eutectics evaluated for the intermetallic NiAl–9Mo

Abstract

Directional solidification (DS) of near-stoichiometric NiAl with a reinforcing refractory metal is of great interest for high-temperature structural applications. A three-dimensional model based on single-crystal plasticity theory is introduced for the description of the creep behavior of DS NiAl–9Mo (at.%) with a well-aligned fibrous microstructure. A hardening model considering also the transition from theoretical to bulk strength is motivated. To evaluate the model, NiAl–9Mo samples were directionally solidified using various growth rates. With the DS samples, creep experiments were performed at 900 °C and 1000 °C for different applied stresses. The model reproduces correctly a change of the applied stress, the temperature as well as a change in the fiber diameter. It is found that creep of the composite is mainly controlled by the plastic behavior of the fibers. A closer insight into the interactions between the fiber and the matrix is obtained by the simulation. Finally, by revealing the impact of each phase on the composite's behavior, the shape of the creep curve could be explained.