Effect of Laser re-melting on the microstructure of High Entropy Alloys

Abstract

• A low density equiatomic High Entropy Alloy Zr-Nb-V-Ti-Al was synthesized. • The as-cast alloy had coarse dendritic structure with compositional inhomogeneities. • Re-melting the as-cast alloy with Nd-YAG Laser resulted in formation of fine grains. • Laser Re-melting significantly reduced inhomogeneities in distribution of Zr & Al. • The microhardness of Laser melted region was found to be similar to the BCC phase. A low density equiatomic High Entropy Alloy of composition Nb-Zr-V-Ti-Al was synthesized for nuclear reactor applications. The alloy in as-cast condition showed a coarse dendritic structure with a major BCC/B2 type dendritic phase while segregation of Zr and Al in the form of intermetallics was noted in the inter-dendrtitic region. Re-melting a part of the alloy surface with an Nd-YAG Laser resulted in formation of very fine grains (∼500 nm) with a significant reduction in compositional segregations with respect to Zr and Al. The microhardness of the Laser melted region was found to be similar to the BCC phase in the as – cast microstrucure. This indicates that Laser melting could be an effective method in reducing compositional and microstructural inhomogeneities and push the multiphase structure towards single phase.