The mechanism of two-step increase in hardness of precipitation hardened CuCoNiBe alloys and characterization of precipitates

Abstract

The precipitation mechanism and microstructure of aged CuCoNiBe alloys have been studied. Two-step increase in the hardness of the material was ascertained and each increase was attributed to the formation of Guinier-Preston (G.P.) zones and precipitation of beryllides utilizing differential thermal analysis (DTA). Composing of different phases capable of precipitation hardening, characterization of the precipitates end up with ternary CoNiBex phase. Detailed FE-SEM analysis revealed that the secondary beryllides responsible for the hardening of the material precipitate inside the primary beryllides which were formed during solidification. Morphology of the precipitates aged at 460 degrees C for 2.5,4 and 24 h was also examined. It was concluded that the precipitates having rod-like morphology for aging 4 h and disk shaped morphology for aging 2.5 and 24 h. (C) 2017 Elsevier B.V. All rights reserved.