Extraordinary superplasticity at low homologous temperature and high strain rate enabled by a multiphase nanocrystalline network

Superplasticity is a highly sought-after property of components manufactured with complex ge-ometries in metal forming processes. However, superplasticity usually occurs at high tempera-tures and/or low strain rates, which entails high energy consumption, long processing time, and severe surface oxidation. Herein, we have developed a multiphase nanocrystalline network (MPNN) in a Ti6Al4V5Cu model alloy, where the grain boundary & beta; phases promote the sliding and rotation of ultrafine & alpha; grains, while the nanosized Ti2Cu particles pin down the & alpha;/& beta; bound-aries to maintain the thermostability of the nanostructure. Results show that the onset temper-ature for superplasticity of the model alloy is 250 degrees C lower than that of the Ti6Al4V alloy at the strain rate of 10-4 s-1. Remarkably, superplasticity was also observed at an extremely high strain rate of 1 s -1 at 750 degrees C, which is 2-4 orders of magnitude larger than conventional superplastic metals. The present work is of great significance in developing more economical and efficient superplastic deformation processes.

Automated summary

Superplasticity at low temperatures and high strain rates has been achieved in a Ti6Al4V5Cu model alloy using a multiphase nanocrystalline network (MPNN). The onset temperature for superplasticity in this alloy is 250°C lower than that of Ti6Al4V alloy, and it exhibits superplasticity even at extremely high strain rates. This research is significant for the development of more economical and efficient superplastic deformation processes.