Phase Formation and Stability in the Pseudobinary Ni sub 3 Al-Ni sub 3 V Alloy System

摘要

In order to study the formation of phases and their thermal stability, DSC (differential scanning calorimetry), x-ray diffraction, and optical microscopy were performed simultaneously in the Ni sub 3 Al-Ni sub 3 V pseudobinary alloy system. For the alloy series represented by Ni sub 3 (Al/sub x/V/sub 100-x/), a tetragonal DO sub 22 phase was found to form for x < 10, and a cubic Ll sub 2 phase for x > 75 at room temperature. For 10 < x < 75, the DO sub 22 and Ll sub 2 phases were found to coexist. Contrary to some theoretical expectations, no complex ordered equilibrium phases formed in this alloy system at any intermediate composition between Ni sub 3 Al and Ni sub 3 V. Measurements of the order-disorder transition temperature, T/sub c/, by DSC, and the associated details of the phase transformations and stability are discussed. (ERA citation 09:048165)