Laser powder bed fusion of TiB2-modified Cu15Ni8Sn alloy: Processability, microstructure and mechanical performance

Abstract

Cu15Ni8Sn is widely used in the aerospace and electronics domains because of its good conductivity and toughness. Due to the material's high laser reflectivity and thermal conductivity, however, employing the laser powder bed fusion (LPBF) additive manufacturing process on Cu15Ni8Sn alloy has been a challenge. This issue was addressed in the present study by modifying the Cu15Ni8Sn powder by adding 1 wt% submicrometre TiB2 ceramic particles. The results indicate that the LPBF's processability was improved by the increased laser absorption rate caused by the addition of 1 wt% TiB2, which eliminated pores and unmelted area defects. The addition of 1 wt% TiB2 also improved the components' surface quality by reducing the surface roughness value of 39.3% compared to the original Cu15Ni8Sn. The findings also indicate that the added TiB2 particles reduced Sn-segregation behaviour, implying that the content and size of the segregated phase could be tailored by the suitable selection of ceramic materials and LPBF process parameters. Another advantage lies in the enhancement of mechanical performance, where a 11% increase in yield strength and 14% increase in ultimate tensile strength were achieved in the LPBF-fabricated modified Cu15Ni8Sn material. In this study, the primary strengthening mechanisms for LPBF-fabricated original Cu15Ni8Sn were found to include dislocation strengthening and grain boundary strengthening. Orowan precipitation strengthening also played a significant role in the Cu15Ni8Sn-1wt.% TiB2 material, as did dislocation strengthening and grain boundary strengthening. These findings provide a promising strategy to improve the LPBF processability of the advanced copper-based materials used in several key fields.