Duplex stainless steels (DSS) are susceptible to thermal aging embrittlement during long-term operation at temperatures in the range 290-325 ℃.The flow behavior of DSS significantly could be different from one of the single phase austenitic or ferric stainless steels.This article overviews the effects of thermal aging DSS on the micro structural evolution after he plastic deformation behavior.After aging at 400 ℃ as long as 10,000 h, austenite play an important role in the plastic activity during tensile deformation, Σ 3 twins boundaries has been found in austenite grains at high level of strain regions.At same time, a few ferrite phase also appears twins for the thermal aging embrittlement.The appearance of these low-angle boundaries is due to the accumulation of dislocations in the material.As deformation proceeds,the matrix losing the KS orientation relationship, the orientation loss become more obvious after aging 10,000h.