| In the present study, tensile properties of continuous casted Cu-9Ni-6Sn alloy, with and without 95% swaging, were examined as a function of continuous casting rates. A large amount of Sn-rich phases were observed in the interdendritic regions of as-casted Cu-9Ni-6Sn alloy, regardless of casting rates. The size and distribution of these phases, however, differ greatly with different casting rates, as well as the amount of Sn in the phase. Slower casting rate tended to increase the size of the phase, but the amount of Sn in the phase increased with faster casting rate. During solutionization, most of Sn-rich phase appeared to decompose into the solid solution. After aging, a significant amount of coarse precipitates were observed in the alloy produced at a casting rate of 280 ㎜/min. It is believed that such coarse precipitates were formed around the Sn-rich phases due to relatively high Sn content after solutionization. SEM fractographic studies indicated that coarse precipitates, as well as weak Sn-rich phases, act as sources for microvoid. Consequently, both tensile strength and elongation of solutionized and aged Cu-9Ni-6Sn alloy increased significantly with decreasing casting rate. Cold swaging greatly improved the tensile properties of Cu-9Ni-6Sn alloy due to the reduced and refined Sn-rich phases and coarse precipitates. |
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