Enhanced high-temperature strength of austenitic steels by nanotwins and nanoprecipitates

A bulk nanotwinned solutionized austenitic steel was prepared by plastic deformation, followed by partial recrystallization treatment. Subsequent aging treatment resulted in extensive precipitation of gamma-prime phase along twin boundaries. These nanoprecipitates are coherent with the austenite matrix on both sides, namely inheriting the twin boundary. The nanotwins constrained by these nanoprecipitates exhibit exceptional thermal stability and efficiently hinder dislocation movement at high temperatures. As a result, the sample exhibits a high yield strength of 780 MPa at 700 ℃. In comparison to the peak-aged coarse-grained sample, the strength at 700 ℃ is increased by ∼60 % in the sample containing ∼49 vol.% nanotwins combined with second phase. This kind of combined strengthening from nanotwins and nanoprecipitates provides a new strategy to further strengthen materials at high temperatures.