Abstract: The microstructure of Cr_(25)Ni_(20)stainless steel under plastic deformation up to 50% has re- vealed an even distributed twins,micro-twins and deformation bands.The σ-phase formation in 800℃ aged specimens is accelerated by its nucleation at either deformation twins or recrystallized grain boundaries under less or more deformation respectively.In the recrystallized zone,the recrystallization is prior to the precipitation of σ-phase.Although recrystallization may accelerate the formation of σ-phase,it is not essential.The twins and micro-twins produced by deformation may also provide the additional nucleation sites.

Key words: plastic deformation, α-phase, recrystallization