Effect of Ni/Ti ratio on the microstructure and mechanical properties of Mo-doped nitial intermetallics

The microstructures and mechanical properties of Ni_50-xTi _43+xAl₆Mo₁ (x= 0.5, 1, 1.5, 3.5, 5.5 and 7 at. %) alloys have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and compressive tests. We found that the variation of Ni/Ti ratio is the predominant reason for affecting the yield stress. The yield stress at room temperature of Ni-rich and Ti-rich alloys was higher than that of the equi-atomic alloy due to the strong solid solution hardening caused by the variation of Ni/Ti ratio. The size and volume fraction of Ti₂Ni phase decreased with increasing Ni/Ti ratio. The yield stress at 600°C and 700°C increased with the increasing volume fraction of Ti₂Ni phase due to the precipitation hardening effect. The precipitation hardening effect was weakened with increasing temperature. For the Ti-rich alloy deformed at 800°C, the yield stress deceased with the increasing of Ni/Ti ratio due to the reduced strength and unfavorable distribution of Ti₂Ni.