The microstructure and phase equilibrium of new high performance high-entropy alloys

In recent years, series of high-entropy alloy have been well developed with high hardness and high temperature stability. These properties could apply in hard surface welding technology. Several AlCrFeMnNi high-entropy alloys have been developed and made as welding rods to apply in the hardface welding on carbon steel using nickel-based alloy as bond coating layer. The hardness of hardface can reach Hv 900 after aging at 700 degrees C for 4 h. One of alloys performed resistant with the thermal effect during hardfacing operation and maintain better hardness in the multiple overlays. An electron probe microanalyzer (EPMA) was used to verify the phase compositions of hardfacing microstructure. There is nanoprecipitate phase formed within the matrix grain and might contribute the high hardness. A primitive phase diagram calculation was done by using the Calphad method. The calculated results show that the hardening mechanism is due to bcc order/disorder coherent strengthening within the matrix grain. Two high-entropy alloys were equilibrated at 700 degrees C for 10 days. The equilibrium phases are consistent with the calculated isopleth. The new phase may relate with FCC phase structure and still under investigation. (C) 2008 Elsevier B.V. All rights reserved.