EFFECTS OF RARE EARTH ELEMENT Gd ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NiAl-Cr(Mo)-Hf EUTECTIC ALLOY

The effects of rare earth element Gd on the microstructure and compressive properties of Ni-33Al-28Cr-5.9Mo-0.1Hf (atomic fraction, %) eutectic alloy at room temperature and 1373 K were studied. Very little amount of Gd dissolved in the NiAl and Cr(Mo) phases, and much more amount of Gd distributed in Heusler phase. Addition of Gd induced the microstructural refinement, including the decrease of the eutectic cell size and the lamellae spacing between the NiAl and Cr(Mo) plates. The proper Gd addition leads to the improvement of the compressive yield strength and ductility of the alloy at room temperature, but Gd has a little effect on the compressive properties at 1373 K. However, the Cr(Mo) phase was coarsened and distributed irregularly when 0.1 Gd (mass fraction, %) was added into the alloy, which resulted in the decrease of compressive properties at the testing temperature.