Effect of Si Addition on Microstructure and Mechanical Properties of Dual Two-Phase Ni₃Al and Ni₃V Intermetallic Alloys

Abstract

The effects of Si addition on the microstructures and mechanical properties of dual two-phase Ni 3 Al and Ni 3 V intermetallic alloys with a composition of Ni 75 Al 9 V 13 Nb 3 (expressed by at%) were investigated, focusing on the substitution manner of Si for Ni, Al or V. Solubility limit of Si in the present microstructure was less than 2 at% Si irrespective of the substitution manner of Si for Ni, Al or V. The eutectoid microstructure in the channel region was degenerated when Si was substituted for V. Third-phase dispersions containing Nb, i.e., Ni 16 Si 7 Nb 6 (G phase: D8a) were present at grain boundaries of the alloys exceeding the solubility limit. In the alloy in which Si was substituted for Ni, unit cell volume of the constituent Ni 3 Al phase increased while that of the constituent Ni 3 V phase little changed. In the alloy in which Si was substituted for Al, unit cell volumes of both phases decreased. The alloys in which Si was substituted for Al or Ni hardened while the alloy in which Si was substituted for V softened. The hardening in the former alloys was attributed to solid solution hardening due to Si substituted for solvent atoms Ni, Al and/or V while the softening in the latter alloy was attributed to the degenerated eutectoid microstructure in the channel region. Also, it was shown that the third-phase dispersions little affected hardness as well as yield strength.

Simulation of the effects of Zr and Co addition on the properties of NiAl-Mo(Cr) alloy

“…Of all the methods available, the alloying method appears to be cost-effective, and simpler with the capability of changing the bond type, electronic structure, and the degree of intermetallic compound long-range order. Previous research on intermetallic compounds like TiAl [9] and Ni3Al [10,11] shows that their properties were significantly improved due to the addition of appropriate alloying elements. So far, extensive research has been conducted on NiAl-based alloys using a number of alloying elements to improve their high-temperature strength and room-temperature plasticity.…”