Understanding the potential of solute trapping induced by rapid solidification in powder bed fusion additive manufacturing

Cu-Ag alloys are known for their exceptional combination of high strength and superior electrical and thermal conductivities. However, conventional manufacturing processes typically produce discontinuous Ag-rich precipitates that degrade performance. Through processing a Cu-5wt.%Ag alloy with electron beam powder bed fusion (PBF-EB), this study reveals the fundamental potential of solute trapping induced by rapid solidification, offering a new pathway to eliminate detrimental discontinuous precipitates. We demonstrate that high solidification rates, exceeding 1 m/s, can be achieved through process control and Cu's inherent high thermal conductivity. This induces significant solute trapping, resulting in a supersaturated Cu matrix during solidification and the precipitation of uniformly dispersed Ag-rich nanoparticles during in-process aging. Consequently, continuous precipitates form, eliminating the detrimental discontinuous precipitates typically persistent in traditional processes. Specifically, the PBF-EB samples exhibit relative densities of up to 98.78% and columnar grain structures with a strong <001> texture along building direction. Grain size varies with process parameters and building height, attributed to the variations in solidification conditions affected by heat accumulation and dissipation dynamics. Through altering solidification segregation, solidification rate can be used to govern the size and morphology of Ag-rich precipitates, thus affecting mechanical and electrical properties. Despite the presence of hot cracks at high-angle grain boundaries, the as-built samples exhibit excellent electrical conductivity (85.9−89.3% IACS) and mechanical properties (maximum hardness of ~87.1 HV, YS of 149 MPa, UTS of 217 MPa), surpassing peak-aged cast counterparts in hardness while maintaining electrical conductivity. These findings establish a generic understanding of solute-trapping-enabled microstructural control in additive manufacturing, providing a foundation for designing high-performance Cu-based alloys for advanced electrical applications. • PBF-EB enables fabrication of Cu-5wt.%Ag alloy with relative density up to 98.78% • A high solidification rate over 1 m/s is achieved by process control • Solute trapping induces precipitation of uniformly dispersed Ag-rich nanoparticles • Discontinuous precipitates are suppressed by rapid solidification