EFFECT OF NI/TI RATIO ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MO-DOPED NITIAL INTERMETALLICS

Abstract

The microstructures and mechanical properties of Ni 50- x Ti 43+ x Al 6 Mo 1 ( 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 Ti 2 Ni phase decreased with increasing Ni / Ti ratio. The yield stress at 600°C and 700°C increased with the increasing volume fraction of Ti 2 Ni 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 Ti 2 Ni .