Interfacial heat transfer mechanism of solidified copper alloys on beryllium copper substrate for twin-roll casting

To provide theoretical guidance and technical support for optimizing solid-substrate heat transfer in twin-roll casting of copper alloys, this study investigates the solid-state interfacial heat transfer behavior of solidified copper alloys on beryllium copper substrate surfaces. A series of heat transfer experiments were designed to simulate the thermal interaction between solidified copper alloys and substrates, in which the initial alloy temperature, substrate material, surface roughness, coating thickness, and surface treatment were varied. Complementary numerical simulations were performed to reveal the coupled thermal mechanisms across microscopic and macroscopic scales. In this study, the coating thickness ranged from 58 to 125 μm, and the surface roughness (Rz) ranged from 1.122 to 3.094 μm. The results demonstrate that the substrate material exerts a dominant influence on heat transfer, with beryllium copper substrates exhibiting significantly higher heat transfer performance than steel substrates. Coatings introduce thermal resistance, and the observed dual heat flux peaks clarify the origin of the plateau in the temperature-time response. The results showed that, at a depth of 5 mm below the top surface of the beryllium copper substrate, when the coating thickness increased from 58 to 125 μm, the substrate temperature decreased from 188 to 137 °C; when the surface roughness (Rz) increased from 1.122 to 3.094 μm, the substrate temperature increased from 179 to 199 °C. Higher initial alloy temperatures and greater substrate surface roughness enhance heat transfer by improving interfacial contact and maintaining continuous heat flux transfer across the interface under compressive loading. Under applied pressure, greater substrate surface roughness enhances heat transfer because the hardness of the solidified copper alloy decreases upon heating, thereby enlarging the effective contact area. On the basis of both the surface morphology and the heat transfer performance of the beryllium copper substrate, the optimal surface roughness (Rz) range was determined to be 1.122∼2.640 μm. This work establishes a quantitative understanding of solid-state heat transfer mechanisms in solidified copper alloys, providing a new framework for optimizing substrate design and surface engineering in high-efficiency twin-roll casting processes.