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采用Thermo-Calc软件对022Cr21Ni2Mn5N双相不锈钢的近平衡态析出相进行了计算分析。采用光学显微镜、透射电镜、物理化学相分析方法对经中温时效处理后试验钢第二相的析出温度、种类、数量和位置进行了观察和研究,并分析了第二相析出行为对钢的冲击韧性的影响机理。结果表明:022Cr21Ni2Mn5N双相不锈钢在600~700℃中温时效时的析出相主要为六方结构的Cr_2N相和面心立方结构的M_(23)C_6相,未见σ相析出。中温时效时,受制于该钢较低的C含量,M_(23)C_6相析出位置仅局限于相界、晶界处。该钢较高的N含量促进钢中Cr_2N相析出,并在相界、晶界和铁素体晶内均有发现。时效初期M_(23)C_6和Cr_2N均具有较高的析出速度,时效时间继续延长析出量增长放缓。时效处理时间和温度直接影响钢的冲击性能:时效初期第二相的快速析出导致钢的冲击功急剧下降;时效足够长时间,第二相析出量达到饱和,钢的冲击功趋于稳定值;并且600℃长时时效时,钢的冲击功值达到最小。
Near-equilibrium precipitates of 022Cr21Ni2Mn5N duplex stainless steel were calculated by Thermo-Calc software. The temperature, type, amount and position of the second phase precipitated after mesophilic aging treatment were observed and studied by optical microscopy, transmission electron microscopy and physicochemical phase analysis. The impact of precipitation of the second phase on the steel Toughness of the mechanism of influence. The results show that the precipitation phases of 022Cr21Ni2Mn5N duplex stainless steel at 600-700 ℃ are mainly hexagonal Cr_2N phase and face-centered cubic C_6 phase, and no precipitation of σ phase occurs. Under medium temperature aging, the precipitation of M_ (23) C_6 phase is confined to the phase boundary and the grain boundary due to the lower C content of the steel. The higher N content of steel promotes the precipitation of Cr 2 N phase in the steel and is found in the grain boundaries, grain boundaries and ferrite grains. At the initial stage of aging, M_ (23) C_6 and Cr_2N both have higher precipitation rate, and the aging time is prolonged and the amount of precipitation is slowed down. The aging time and temperature directly affect the impact properties of steel: the rapid precipitation of the second phase leads to a sharp drop of the impact energy of the steel during the early aging; the aging time is long enough for the precipitation of the second phase to reach saturation and the impact energy of the steel tends to be stable; And 600 ℃ long time aging, the impact energy of steel to a minimum.