THE EFFECT OF RARE EARTH ELEMENTS ON Cr PRECIPITATIONS IN A Cu-0.8WT%Cr ALLOY

Abstract

The microstructural evolution of Cu-based alloys during aging was studied using a quantitative metallographic method. Samples were cut from ingots of Cu-0.8wt%Cr and Cu-0.8wt%Cr-RE alloys. These were solution treated at 1000 ºC for 1.5h and subsequently quenched in water, then separately aged at 480 ºC for different durations. The microstructures were observed by optical microscope, and the characteristic geometric parameters of precipitated Cr phase, including volume fraction V V , face density N A , mean diameter and roundness, were measured. These data provided more details about the process of aging. The results showed that precipitation of Cr phase occurred in the form of particles during aging. Rare earth elements promoted the precipitation of Cr phase and dispersed Cr particles. The phenomenon of overaging came earlier in Cu-Cr-RE than in Cu-Cr. In the present work, the optimal aging time at 480 ºC was 2 hrs for the Cu-0.8wt%Cr-RE alloy and 3 hours for the Cu-0.8wt%Cr alloy.

Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM

“…Indeed, many authors [18,23,44,45] stated that Cu-Cr-Zr, after solution annealing in the range of 930-1 050 • C, becomes fully free from any precipitate or cluster. Other studies [12,43,46] evidenced the presence of Cr clusters caused by incomplete dissolution. The present results confirm the fact that SANS is a powerful method that is very sensitive to small variations in the nano-objects size.…”

Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM

“…Indeed, many authors [18,23,44,45] stated that Cu-Cr-Zr, after solution annealing in the range of 930-1 050 • C, becomes fully free from any precipitate or cluster. Other studies [12,43,46] evidenced the presence of Cr clusters caused by incomplete dissolution. The present results confirm the fact that SANS is a powerful method that is very sensitive to small variations in the nano-objects size.…”

Effects of Zr and (Ni, Si) additions on properties and microstructure of Cu–Cr alloy

“…The variations of precipitates morphology can be associated with the interface energy between precipitates and matrix [33,34]. As we all know, the interface energy of spherical precipitated particles is lower than the needle-like and thin-plate precipitates [35]. Since precipitates with large aspect ratio in Cu-Cr alloy possess high interface energy with matrix, lowering the interface energy of precipitates become the main driving force for the spheroidization of precipitates in Cu-Cr-Zr and Cu-Cr-Zr-Ni-Si alloy.…”