Enhancing the interface strength of additively manufactured 316 L/CuSn10 bimetallic components through heterogeneous microstructures

Abstract

Bimetallic structures combining steel and copper offer the advantage of merging robust mechanical strength of steel with exceptional thermal conductivity of copper, making them valuable in applications such as cooling channels, heat-exchange equipment, and aviation industries. Nonetheless, creating a high-strength bimetallic interface proves challenging due to the inherent disparities in their physical and chemical properties. In this investigation, we present a novel approach to tailor the microstructure of laser powder bed fused steel-copper bimetallic structures, aiming to enhance their interface strength significantly. The resulting steel-copper bimetallic structure exhibited remarkable interface strength, boasting an ultimate tensile strength of 619 MPa. This enhanced strength can be attributed to the presence of a heterogeneous interlayer structure proximate to the interface. This heterogeneity manifests as a gradient microstructure consisting of two columnar crystal outer layers and an equiaxed crystal interlayer. This microstructural diversity engenders a substantial back stress during plastic deformation, thus yielding a synergistic strengthening effect. Furthermore, these heterogeneous structures exert control over the fracture behavior of the samples, shifting it from cleavage fracture to ductile fracture. Consequently, this study introduces an innovative approach for optimizing and fine-tuning the microstructure of interfaces comprising multi-materials.