Influences of Yttrium on Microstructure and Mechanical Properties of NiAl-28Cr-5.5Mo-0.5Hf Alloy

The influences of yttrium on the microstructure and mechanical properties of NiAl-28Cr-5.5Mo-0.5Hf alloy were investigated by using SEM, XRD and compressive tests, respectively. The study indicates that the compressive strength and ductility of 0.05% Y(mass fraction)-containing alloy are superior to those of other alloys at the strain rate of 1.94×10 -3 s -1 over a range from room temperature to high temperature. It is also found that the microstructure of alloys is refined gradually with increasing Y content. This is reflected by more grain cells, finer spacing between Cr(Mo) fibers and smaller Cr(Mo) rods at the grain boundary. When 0.1% Y(mass fraction) and above are added to the matrix, the yttrious compounds of Y 2Ni 17 and Al 3Y form at the interfaces between NiAl and Cr(Mo) phases, which leads to the decrease of strength and ductility. Therefore, the proper addition of Y can improve the compressive strength and ductility of the alloy.