Microstructure and fracture toughness of Cr/Cr₂Nb alloys with trace Y addition

The microstructures of binary Cr/Cr₂Nb alloys doped with 0.1 at-% rare earth element (REE) Y were characterised by fine interlamellar spacing, and the growth morphology of Cr₂Nb primary phase was transformed from faceted to non-faceted. Moreover, the lamellar spacing was observed to decrease with the decreasing of solidification rate with the addition of REE Y. Furthermore, the mechanical tests showed that the addition of REE Y has a beneficial effect on the room temperature fracture toughness of Cr₂Nb/Cr alloys. The room temperature fracture toughness of the Y doped Cr/Cr₂Nb hypoeutectic and hypereutectic alloys increased by ,130 and 140% over that of the undoped alloys respectively, which was caused by the refinement of lamellar eutectic and strengthening of lamellar eutectic bonding strength.