Phase relationships of the La-Ni-Mg system at 500 °C from 0 to 66.7 at.% Ni

The La-Ni-Mg phase diagram between 0 and 66.7 at.% Ni has been investigated at 500 °C by means of scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray powder diffraction (XRD). The isothermal section studied includes seven ternary compounds. The binary boundary phases do not generally show any appreciable solubility in the ternary field. The composition and crystal structure of the two ternary phases LaNiMg2 and La2Ni2Mg have been confirmed. The ternary phase (La1 − xMgx)Ni2 has been detected on the composition line at 66.7 at.% Ni, crystallizing in the cubic MgCu4Sn-type structure and existing in the compositional range 0 < x ≤ 0.60. The LaMg2 cubic phase (MgCu2 Laves type) has been found to be stabilized at 500 °C by a small amount of Ni. Three new ternary phases have been found in the La-rich region.