Influence of high pressures on the formation of new phase in the Al$_{86}$Ni$_2$Со$_6$Gd$_6$ alloy

The structure, elemental and phase composition of the eutectic alloy Al$_{86}$Ni$_2$Со$_6$Gd$_6$ (hereinafter referred to as at.%) During the solidification of the melt from 1500$^\circ$C at a rate of 1000$^\circ$C/s under high pressure of 3 and 7 GPa have been investigated by X-ray diffraction analysis and electron microscopy. Solidification of the melt under high pressure leads to a change in the phase composition of the alloy and the formation of an anomalously supersaturated solid solution of $\alpha$-Al(Gd). At a pressure of 7 GPa, new phases were synthesized: Al$_3$Gd$^*$ (like Al$_3$U) containing Co and Ni, with a primitive cube structure (cP4/2) with a lattice parameter $a$ = 4.285 $\pm$ 0.002 $\mathring{\mathrm{A}}$ and Al$_8$Co$_4$Gd$^*$ (like Al$_8$Co$_4$Gd) with a tetragonal structure (tI26/1) with parameters $a$ = 8.906 $\pm$ 0.003 $\mathring{\mathrm{A}}$ and $c$ = 5.150 $\pm$ 0.003 $\mathring{\mathrm{A}}$. The structure of all the samples obtained is homogeneous, dense, finely dispersed, without shrinkage cavities and pores. The average microhardness of the samples is high due to solid solution and precipitation hardening.