Effect of V addition on microstructures and mechanical properties of Cu-15Ni-8Sn alloy

The effect of V addition on the microstructure and mechanical properties of Cu-15Ni-8Sn alloy was systematically investigated in the present study. The results indicate that the significant grain refinement can be achieved by adding trace V content for Cu-15Ni-8Sn alloy, which is ascribed to the formation of V-bearing intermetallic compound. Besides, the addition of V also brings obvious change in the morphology around grain boundary. After solution treatment at 850 degrees C for 4 h, considerable Ni3V particles precipitate from the matrix, which can hinder the grain boundary migration and remain the grain refinement effect. Besides, it can also significantly influence the microstructure and its resulting mechanical properties of the alloy during the subsequent aging process. Moreover, it was found that, after aging treatment at 400 degrees C, Cu-15Ni-8Sn alloy can possess excellent softening resistance with an appropriate addition of V. Namely, it can maintain a high hardness and ultimate tensile strength with the extension of aging time. In addition, the grain refinement and the suppression of discontinuous precipitation by Ni3V particles are believed to be responsible for the improving strength. Especially, when aging for 4 h, the ultimate tensile strength increases from 899 MPa (Cu-15Ni-8Sn) to 990 MPa (Cu-15Ni-8Sn-0.4V). The optimal comprehensive performance can be obtained for Cu-15Ni-8Sn-0.4V alloy with a hardness (368 HV), ultimate tensile strength (990 MPa), electrical conductivity (8.03%IACS) when aging at 400 degrees C for 4 h.