Hot stamping of ultra-thin titanium sheets: mechanical properties, fracture limit and process verification

Owing to the competitive advantages such as a high strength-to-weight ratio and excellent corrosion resistance, ultra-thin titanium sheets are considered one of the most promising bipolar plate substrates for proton exchange membrane fuel cells and are receiving increasing attention. However, due to their limited formability at room temperature, titanium bipolar plates are challenging to form, especially as the complexity of the flow channels increase continuously. In this study, the flow behavior and mechanical properties of ultra-thin titanium sheets at elevated temperatures were investigated, and their fracture limits were characterized to provide guidance for determining the process window. Finally, a lab-scale titanium bipolar plate was trial-fabricated using hot stamping at 700 ℃ with an on-site electric heating system. The results reveal that both the forming limit and dimensional accuracy of the titanium bipolar plates can be clearly improved, confirming the feasibility of the hot stamping process.