Microstructures and mechanical properties of NbCr2 and ZrCr2 Laves phase alloys prepared by powder metallurgy

Abstract

Microstructures, mechanical properties and oxidation behavior were investigated on NbCr2 and ZrCr2 Laves phase alloys prepared by powder metallurgy (P/M), and also by arc-melting, i.e. ingot metallurgy (I/M). These properties were also evaluated, in terms of alloying, heat treatment and alloy stoichiometry. High-temperature yield strength and brittle ductile transition temperature (BDTT) were generally lower in alloys prepared by P/M process than in those prepared by I/M process while micro hardness and fracture toughness were higher in alloys prepared by P/M process than in those prepared by I/M process, irrespective of NbCr2 or ZrCr2 alloys. Also, high-temperature strength and micro hardness were higher in NbCr2 alloys than in ZrCr2 alloys while fracture toughness was lower in NbCr2 alloys than in ZrCr2 alloys, irrespective of P/M or I/M process. For oxidation behavior at 1223 K, NbCr2 alloys showed linear increase with increasing time accompanied with irregular fluctuation, while ZrCr2 alloys showed parabolic increase with increasing time. It was also found that alloy stoichiometry greatly affected micro hardness, fracture toughness and oxidation behavior in ZrCr2 alloys.