Effect of heat treatment on tensile properties and fracture behavior of LPBF-manufactured Cu–10Al and Cu–10Sn alloys

This study investigates the tensile strength, fracture behaviour and heat treatment of copper alloys fabricated by laser powder bed fusion (LPBF) process. Two copper alloys with 90% Cu-balance are considered in this study, namely, Cu–10Al (aluminium bronze) as lightweight copper alloy with high mechanical strength and Cu–10Sn (tin bronze) for high ductility, and wear–corrosion resistance. Cu–10Al exhibits higher strength with a mixed brittle–ductile fracture mode, while Cu–10Sn shows a predominately ductile with dimpled fracture morphology. After heat treatment, both Cu–10Al and Cu–10Sn experience a reduction in strength, accompanied by a significant improvement in ductility. As-built Cu–10Al shows about ≈ 700 MPa strength with low ductility (≈ 5–7%); Heat treatment triples elongation/ductility but lowers the strength and hardness (≈ 20–25%). Conversely, as-manufactured Cu–10Sn has half the strength and double the strain rate compared to Cu–10Al in the same SLM manufacturing parameters (constant volumetric energy density), and annealing doubles its elongation with minimal strength loss. Surface metrology analysis of the fracture cross-section confirmed that heat treatment reduced surface irregularities and promoted a more homogeneous ductile fracture morphology, particularly in Cu–10Sn.