Microstructure and mechanical properties of arc melted Cr-Cr₂Nb hypoeutectic alloy

The microstructure and mechanical properties of a binary Cr based alloy containing the Laves phase Cr₂Nb and Cr phase have been studied in the arc melted condition. Microstructure consisting of fine directional divorced eutectic was observed at the bottom of the ingot, while it developed into coarse Cr primary dendrites plus interdendritic lamellar eutectic containing Cr₂Nb and Cr phases in the middle and top parts of the ingot. Meanwhile, the fracture toughness values of the top and bottom parts of the ingot attained 4·5 and 7·8 MPa m^1/2 at room temperature, which were about three and five times than that of monolithic Cr₂Nb respectively. The enhancement was explained by the second Cr phase toughening and grain refinement toughening mechanisms. In addition, the formation mechanism of the divorced eutectic and the microstructure-property relationships were also discussed.