Metal Micro-forming of AA5052 Using High-durable Glassy Carbon Mold for Efficient Boiling Heat Transfer

Micropatterned glassy carbon (GC) has been introduced as a mold for the metal micro-forming owing to its excellent hot hardness. However, the durability of the mold is a crucial matter for industrial adoption of the technology because the micropattern can be easily damaged due to the thermal shrinkage of the metal workpiece. In this study, we fabricated a GC mold with filleted-micropost pattern by utilizing spin-coating to enhance the durability of the mold. As a result of the molding tests, the filleted-micropost pattern demonstrated excellent durability compared to the bare micropost pattern with sharp corners. Because its smooth surface profile not only reduces stress concentration, but it induces the natural release of the mold from the formed metal, which occurred during the cooling stage. Finally, we confirmed that the proposed method can improve the thermal efficiency of heat exchangers, because the pool boiling performance of the micro-formed AA5052 surface showed 34% and 102% enhancement in critical heat flux and maximum heat transfer coefficient, compared with that of the smooth surface, respectively. The proposed method can be a breakthrough to address the limitations of conventional microfabrication processes to facilitate low-cost and environment-friendly mass production.