Due to isothermal heat treatment or welding,duplex stainless undergoes a variety of decomposition processes at a temperature ranging from 300 - 1 100℃,which could form inter-metallic phases likeσ-phase and xphase,as well as Cr_2N and M_(23)C_6,etc.These processes are not only influenced by temperature and cooling speed, but also are affected by alloy element content.The purpose of the research was to work out the qualitative and quantitative analysis of precipitate phases in 2 205 duplex stainless steel with different isothermal heat treatment situation.After choosing the electrolyte and electrolytic systems,we use electrochemical method to extract precipitate phases from the matrix.Scanning electron microscope(SEM) and X-ray diffraction(XRD) were used to examine their modality and structure.Particle size distribution was performed by dynamic laser scattering sizer (DLS-Sizer).Furthermore,oxygen-nitrogen analyzer and carbon-sulfur analyzer were applied to measure the content of nitrogen and carbon in precipitate phases.Separation and quantitative analysis of precipitate phases were carried out by wet chemical analysis and inductively coupled plasma spectrometry(ICP).In a word,combining chemical and physical methods,our research reveals the transformation of precipitate phases’species,content, elemental composition and particle size distribution during different isothermal heat treatment situation. Due to isothermal heat treatment or welding, duplex stainless undergoes a variety of decomposition processes at a temperature ranging from 300 - 1 100 ° C, which could form inter-metallic phases like σ-phase and xphase, as well as Cr_2N and M_ (23) C_6 , etc. These processes are not only influenced by temperature and cooling speed, but also are affected by alloy element content. The purpose of the research was to work out the qualitative and quantitative analysis of precipitate phases in 2 205 duplex stainless steel with different isothermal heat treatment situation. After choosing the electrolyte and electrolytic systems, we use electrochemical method to extract precipitate phases from the matrix. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to examine their modality and structure. Particle size distribution was performed by dynamic laser scattering sizer (DLS-Sizer). Ferrthermore, oxygen-nitrogen analyzer and carbon-sulfur analyzer were applied to measure the content of nitr ogen and carbon in precipitate phases. Separation and quantitative analysis of precipitate phases were carried out by wet chemical analysis and inductively coupled plasma spectrometry (ICP). In a word, combining chemical and physical methods, our research reveals the transformation of precipitation phases’ specifics , content, elemental composition and particle size distribution during different isothermal heat treatment situation.