Age-induced precipitation and hardening behavior of Ni₃Al intermetallic alloys containing vanadium

L1₂-type Ni₃Al alloys containing vanadium are potential candidates for solid-solution and age-hardenable alloy systems, according to the Ni₃Al-Ni₃V pseudo-binary phase diagram. Therefore, herein, variations in the microstructure and mechanical properties of Ni-13 at.% Al-12 at.% V-50 ppm B alloy during isothermal aging were investigated. Alloy specimens were solution-treated at 1323 K for 48 h, quenched in water, and aged at 1073 K to 1173 K. The quenched specimens exhibited a single phase of Ni₃Al (L1₂ structure derived from Al (fcc) structure), while in the aged specimens, numerous fine disk-shaped precipitates identified as Ni₃V (D0₂₂ structure from orthorhombic structure) were formed on {001} planes of the Ni₃Al matrix. The size of the disk-shaped Ni₃ V precipitates increased gradually with increasing aging period. The hardness and strength of the specimens increased initially during aging at 1073 K to 1173 K, reached a maximum, followed by a subsequent decrease. The age-hardening behavior observed for the specimens can be explained in terms of precipitation of the fine disk-shaped Ni₃ V precipitates in the Ni₃ Al matrix. Furthermore, the peak-aged specimens exhibited an increase in yield strength with increasing testing temperature, similar to other L1₂-type intermetallic alloys.