Improved mechanical and thermophysical properties of additively manufactured Cu-Ni-Sn-P alloy by using aging treatment

Abstract

This study investigated ways to improve both the mechanical and thermal properties of a Cu-Ni-Sn-P alloy manufactured with selective laser melting (SLM) using aging treatment. Homogenization heat treatment was conducted to the alloy at 820 °C for 12 h, and aging heat treatment was applied at 400 °C for 0.25, 0.5, 1, 2 and 4 h. Initial microstructure analysis identified (Cu, Ni)3P phase precipitates of a few μm in size, and the size and fraction of precipitates increased as aging heat treatment time increased. Room temperature compressive tests on the homogenized sample identified a yield strength of 135.7 MPa. Meanwhile, the yield strength of the sample that underwent 2-hour aging treatment measured 454.5 MPa, indicating a three times greater improvement of the mechanical properties than the homogenized sample. This was confirmed to have been contributed by precipitation hardening from the increased precipitate size and fraction as a result of aging treatment. In addition, thermal conductivity also increased as aging treatment was performed. In particular, an aging time greater than 2 h achieved an approximately 30% increase in thermal conductivity compared to the homogenized sample. Through aging treatment, both the mechanical property and thermal conductivity of an SLM-built Cu-Ni-Sn-P alloy were improved. Based on these findings, this study also discussed the underlying mechanisms according to aging time with respect to microstructural changes.