Description of the superplastic flow process by deformation mechanism maps in ultrafine-grained materials

Abstract

The synthesis of ultrafine-grained (UFG) materials is very attractive because small grains lead to excellent creep properties including superplastic ductility at elevated temperatures. Severe plastic deformation (SPD) is an attractive processing technique for refining microstructures of metallic materials to have ultrafine grain sizes within the submicrometer to even the nanometer level. Among the SPD techniques, most effective processing is conducted through equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) and there are numerous reports demonstrating the improved tensile properties at elevated temperature. This report demonstrates recent results on superplasticity in metals after ECAP and HPT. Moreover, superplastic flow of the UFG materials is evaluated by using flow mechanisms developed earlier for coarse-grained materials and depicted by plotting deformation mechanism maps which provide excellent visual representations of flow properties over a wide range of testing conditions. © 2016 Trans Tech Publications, Switzerland.