Bulk intermetallic compound in Ni-Al system by low-time mechanical alloying followed by spark plasma sintering

In this research, formation of Ni۳Al intermetallic compound was investigated using mechanical alloying (MA) of Ni and Al powders, spark plasma sintering (SPS) and subsequent annealing. In this regard, mixture of primary powders with composition of Ni۷۵Al۲۵ was mechanically alloyed for ۱۵ h and then sintered using spark plasma method at ۶۰۰ °C under ۴۰ MPa pressure for ۲۰ min. Furthermore, annealing cycles was applied at ۶۰۰ °C for ۲ h and ۱۰۰۰ °C for ۱, ۱۰ and ۲۰ h. Phase evolution, microstructure and hardness were assessed using X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and Vickers hardness test. Results indicated that the synthesized sample consisted of mainly Ni(Al) phase with a small amount of Ni۳Al/Ni۲Al۳ intermetallic compounds. With increasing annealing time and/or temperature, the amount of intermetallic compounds increased. Hardness value also rose from ۱۶۲ to ۲۰۳ HV by increment in annealing temperature and time, due to higher fraction of intermetallic phases.

Keywords:

Mechanical alloying(MA) , nickel-aluminide , spark plasma sintering(SPS) , intermetallics , Ni۳Al.