Phase relations of the Sm-Ni-Al ternary system at 500°C in the 40-100 at.% Al region

The isothermal section at 500 °C of the Sm–Ni–Al ternary system in the 40–100 at.% Al region has been investigated by means of optical and electronic microscopy, quantitative microprobe microanalysis and X-ray powder diffraction. At this temperature six intermetallic phases have been determined. The existence of the Sm4Ni6Al23, SmNiAl4, SmNiAl2 and SmNiAl phases, already known in the literature, was confirmed. Two new intermetallic phases and their crystal structures were determined, SmNiAl3, oP20-YNiAl3 type and SmNi2Al3, hP18-HoNi2.6Ga2.4 type. The phase relationships have been established and two ternary eutectic equilibria in the Al-rich region have been identified: E1, Ni-rich: Al + NiAl3 + Sm4Ni6Al23 and E2, Sm-rich: Al + SmAl3 + Sm4Ni6Al23.