Abstract
Duplex structure Cu-Cr alloys are widely used as contact materials. They are generally designed by increasing the Cr content for the hardness improvement, which, however, leads to the unfavorable rapid increase of the electrical resistivity. The solidification behavior of Cu100−xCrx (x = 4.2, 25 and 50 in wt.%) alloys prepared by laser rapid solidification is studied here, and their hardness and electrical conductivity after aging are measured. The results show that the Cu-4.2%Cr alloy has the most desirable combination of hardness and conductive properties after aging in comparison with Cu-25%Cr and Cu-50%Cr alloys. Very importantly, a 50% improvement in hardness is achieved with a simultaneous 70% reduction in electrical resistivity. The reason is mainly attributed to the liquid phase separation occurring in the Cu-4.2%Cr alloy, which introduces a large a
Highlights
Great research interest has been devoted to Cu-Cr alloys in the past few decades as the alloys are the most commonly used contact materials in medium-voltage and high-current vacuum interrupters [1,2,3]
Once the Cu-Cr melt achieves a sufficient undercooling and cools into the liquid miscibility gap, the Cr-rich strengthening phase will nucleate through the liquid phase separation (LPS) process and form particulates to disperse in the Cu-rich matrix [1,2,3]
It can be seen that a large amount of spherical white Cr-rich phases are observed and well dispersed in the dark Cu-rich matrix, suggesting that the LPS can occur in the Cu-4.2%Cr alloy
Summary
Great research interest has been devoted to Cu-Cr alloys in the past few decades as the alloys are the most commonly used contact materials in medium-voltage and high-current vacuum interrupters [1,2,3]. It has been well known that a liquid miscibility gap exists in the Cu-Cr binary phase diagram, due to a large positive mixing heat between Cu and Cr in the liquid state. Once the Cu-Cr melt achieves a sufficient undercooling and cools into the liquid miscibility gap, the Cr-rich strengthening phase will nucleate through the liquid phase separation (LPS) process and form particulates to disperse in the Cu-rich matrix [1,2,3]. Mostly by the containerless solidification, have been made to investigate the undercooling effect in Cu-Cr alloys and it has been proved that the properties of Cu-Cr alloys are strongly dependent on their solidification behavior, compositions, aging effects, and the morphology of the Cr phase [3,4,5].
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