Overview: Using Severe Plastic Deformation in the Processing of Superplastic Materials

In tensile testing, polycrystalline materials generally fail at relatively low total elongations but under some limited conditions it is possible to achieve exceptionally high elongations of up to and exceeding 400%. This superplastic condition is important scientifically but also it has important uses through the industrial development of superplastic forming operations. This overview traces the historical development of this superplastic effect and it provides a summary of the main characteristics of the superplastic flow process. Conventional thermomechanical processing is not able to produce exceptionally small grain sizes within the submicrometer or nanometer range but this limitation was effectively overcome through processing using severe plastic deformation (SPD). The advantages of SPD processing are discussed and examples are presented. Finally it is demonstrated that the experimental data may be easily and effectively displayed through the construction of deformation mechanism maps based on combinations of stress, grain size and temperature. [doi:10.2320/matertrans.MT-MF2022021]

Automated summary

In tensile testing, polycrystalline materials usually fail at low total elongations, but under certain conditions, exceptionally high elongations of over 400% can be achieved. This superplastic condition is not only important scientifically, but also has significant industrial applications in superplastic forming operations. This overview traces the historical development of the superplastic effect and summarizes the main characteristics of the superplastic flow process. Severe plastic deformation (SPD) processing has effectively overcome the limitation of producing exceptionally small grain sizes within the submicrometer or nanometer range. The advantages of SPD processing are discussed and illustrated with examples. Additionally, the construction of deformation mechanism maps based on stress, grain size, and temperature combinations is shown as an effective way to display experimental data.