Effect of sintering pressure and temperature on structure and properties of Ni Al metal-intermetallic composites produced by SPS

Abstract

In recent decades, spark plasma sintering (SPS) has become a widespread technique in the production of high-quality intermetallic-based materials. In this study, we used SPS to fabricate multilayer metal-intermetallic (MIL) composites from pure nickel and aluminum foils. The effect of sintering temperature and pressure on the structure and properties of the fabricated MIL composites is discussed. The sintering temperature was changed from 900 to 1100 °C, the pressure varied from 10 to 40 MPa. The structure of the materials was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy-dispersive spectroscopy (EDX), and X-ray diffraction (XRD). Depending on the sintering regimes the intermetallic layers in the composites consisted of Ni 2 Al 3 , Ni 3 Al, and NiAl of cubic and tetragonal modifications. Tetragonal NiAl appeared in the form of microtwinned lamellar martensite. A change in SPS temperature from 900 to 1100 °C led to an increase in the volume fraction of nickel-enriched intermetallic compounds, which was accompanied by improving composites strength. With an increase of the SPS pressure from 10 to 30 MPa, the number of pores and cracks in composites decreased. At the same time, their bending strength increased by 2 times (from 450 to 900 MPa). Fractographic studies showed that the fracture mechanism of the intermetallic layers depends on their elemental composition and varies from brittle transcrystalline to wavy “feathery”. • Multilayer metal-intermetallic composites were produced by spark plasma sintering. • Ni 2 Al 3 , NiAl, and Ni 3 Al compounds were formed in the intermetallic layers. • Increase in temperature led to an increase in the volume fraction of Ni-rich phases. • NiAl twinned lamellar martensite was formed after sintering at 1100 °C. • Increase in pressure and temperature increased tensile and bending strength.