A true change of NiAl-Cr(Mo) eutectic lamellar structure during high temperature treatment

A true change of NiAl-Cr(Mo) eutectic lamellar structure during high temperature treatment is investigated at 1150 °C (≈0.8Tm). The result indicates that the lamellar structure is instable, and the lamellar structure at the eutectic cell center possesses poorer stability compared to that at the eutectic cell boundary. The deep etching demonstrates that the pinching off and spheroidization of Cr(Mo) lamellae observed by mild etching are not true. A true case is that only local dissolution of Cr(Mo) lamellae (corresponding to pinching off) occurs. In particular, the observation way inclining 45° to growth direction could clearly verify that the spheroidization of Cr(Mo) lamellae does not occur, and actually the cylinderization of Cr(Mo) lamellae occurs. The relative instability mechanism is also discussed. [Display omitted] •NiAl-Cr(Mo) eutectic lamellar structures are instable at 1150 °C (≈0.8Tm).•The lamellar structure at the eutectic cell center possesses poorer stability.•Pinching off and spheroidization of Cr(Mo) observed by mild etching are not true.•Deep etching and observation of inclining 45° to growth direction reveal the truth.•A true case is that local dissolution and cylinderization of Cr(Mo) lamellae occur.