Precipitation behavior of the M23C6 phase on the coherent twin boundary of 25Cr-20Ni-Nb-N steel

Abstract

The precipitation behavior of M23C6 on random and coherent twin boundaries in aged 25Cr–20Ni–Nb–N steel was characterized. M23C6 on a random boundary has a cube-on-cube orientation relationship with a single-grain side and no orientation relationship with the other side. NbX was precipitated at the coherent interface on the random boundary. Two M23C6 particles were precipitated on both sides of the coherent twin boundary with a (111)M23C6-A//(111)M23C6-B and [110]M23C6-A//[110]M23C6-B orientation relationship, which is identical with that of the coherent twin boundary of austenite matrix. As a result, the M23C6 twin was formed at the original twin boundary. Both sides of the matrix/M23C6 interfaces satisfied a cube-on-cube orientation relationship with faceted interfaces parallel to (111)γ and (111)M23C6. NbX is precipitated at the M23C6 twin boundary.