Investigation of the Ni$_3$Al-based alloys microstructure crystallized by different methods

Ingots for the investigation were prepared from Ni$_3$Al-based cast alloys and crystallized by different methods. Ingots 1 and 4 were prepared by smelting in an open induction furnace SELT-20C/20 and cooling in metal casting mold. Ingots 2 and 5 were smelt in the open induction furnace SELT-20C/20 and cooled in ceramic casting molds. Ingots 3 and 6 were prepared by smelting in the open induction furnace SELT-20C/20 with casting in the consumable-electrode shape followed by electroslag remelting and cooling in a copper water-cooled mold. The prepared ingots have the chemical composition presented in Table.

The samples selected from the prepared ingots were investigated. As a result of the present work, the technology for the preparation of ingots from Ni$_3$Al-based alloys in an open induction furnace has been developed. The microstructure of the samples crystallized by different methods has been studied. It is shown that when the melts of the studied systems are being cooled, their hardening follows the same mechanism: the formation of primary crystals of intermetallic compound Ni$_3$Al $\rightarrow$ crystallization of eutectic (intermetallic compound Ni$_3$Al + Ni-based solid solution). It is established that cooling of melts in steel and ceramic molds leads to the formation of transverse cracks. At cooling in a copper water-cooled mold, cracks do not form. Based on the results obtained it has been found that the optimal method for the preparation of work pieces for piercing mandrels is smelting in an open induction furnace with casting in consumable-electrode shape followed by electroslag remelting and cooling in a copper water-cooled mold.