Mechanism of segregation on the tensile and fracture behaviors of CuSn10P1 alloy

Abstract

The effects of segregation and δ-Cu₄₁Sn₁₁ on the strength and ductility of the CuSn10P1 alloys have been revealed. The hard and brittle δ-Cu₄₁Sn₁₁ prevents dislocations from passing through the interface and transfer of plastic slip between the matrix and the δ-Cu₄₁Sn₁₁. The plastic slip in the matrix is blocked completely near the interface, resulting in stress concentration. Because of Sn segregation, its solid solution strengthening effect in the dendrite stem and interdendritic region is different. The poor plastic deformation ability of the interdendritic region greatly hinders the movement of the dislocations, resulting in a deformation inhomogeneity between the dendrite stem and the interdendritic region. The stress concentration caused by the blocking effect of plastic slip and deformation inhomogeneity promotes the crack initiation and propagation, which are the fundamental reasons for the low strength and plasticity. The as-cast alloy has a strength and elongation of 305.3 MPa and 12.5 %, respectively. The heat treatment can effectively eliminate the segregation and δ-Cu₄₁Sn₁₁, improving the deformation uniformity between dendrite arms and interdendritic regions. During the tensile process, cracks are not prone to initiation and propagation. Consequently, both the strength and ductility of the alloy are enhanced. Holding at 600 °C for 1.0 h is a reasonable heat treatment process to improve the comprehensive properties of the alloy. The strength and elongation of the alloy heat-treated at 600 °C for 1.0 h reached 363.1 MPa and 32.7 %, respectively.