Explanation

Some materials exhibit extremely high plasticity under certain structural states (such as ultra-fine grains), certain temperatures and deformation rates, which is called superplasticity. The room temperature elongation of general industrial materials ranges from a few percent to dozens of percent, but the elongation of superplasticity materials can be as high as hundreds or even thousands of percent. There are three conditions to produce superplasticity: first, the grain size should be fine, second, the temperature should be high (generally greater than half of the melting point), and third, the value should be large. The finer the grain size is, the higher the temperature is, and the strain rate range where superplasticity can occur also increases. The diffusion controlled grain boundary slip mechanism in creep theory can be used to explain the superplasticity phenomenon under low stress. superplasticity was first found in Al Zn alloy, and later in iron base, iron nickel base alloy, titanium alloy and ceramics, superplasticity was also found and has been applied in industry. Because materials is in superplasticity state, its formability will be greatly improved and molding stress can be greatly reduced.

Classification