Effects of Ti and High Cooling Rate on the Phase Equilibria and Properties of Ni3(Al,V) Alloys

Abstract

Investigations of the Ni3(Al,V,Ti) alloys with 5 at.% Ti addition show that high quenching rates from the liquid state allow for the preservation of the metastable Ni(Al,V,Ti) solid solution at low temperatures as well as for the limitation of the eutectoid decomposition range. Annealing at the temperatures close to the eutectoid decomposition causes an increase in the amount of the Ni3Al and Ni3V equilibrium phases, as well as the precipitation of the Ni3Ti phase. The V addition reveals the ability to stabilize Ni solid solution, while Ti retards Ni3V phase precipitation but also supports the precipitation of the Ni3Ti phase, in spite of the higher than 5 at.% range of Ti solubility in the Ni3V phase. The increase in V and Ti content at the cost of a decrease in Al content strongly increases micro-hardness of the alloys crystallized at high rates. For the alloys containing predominantly V, increased ductility was noticed in the temperature range of the dissolution of Ni3V precipitates.