通过JMatPro软件,计算预测254SMo超级奥氏体不锈钢(SASS)和2507超级双相不锈钢(SDSS)中σ相的热力学析出条件,并制定了不同的热处理制度;同时借助光学显微镜、扫描电镜等手段分析研究了经不同温度时效不同时间后σ析出相的形态及析出机理.结果表明:254SMo SASS在1020℃不同时效时间下,在晶界上析出富含Cr、Mo和低Ni的σ相.随着时效时间增加,σ相数量增多、尺寸增大,且呈短棒状、长条状和胞状等形态,并按照γ→σ方式析出;2507 SDSS在950℃不同时效时间下,在α/γ界面和α/α晶界处析出富含Cr、Mo和更低水平Ni的σ相.随着时效时间增加,σ相数量增多,向铁素体内部长大并最终呈网状分布在奥氏体基体上,且伴有二次奥氏体(γ2)生成,其是按照α→σ+γ2方式析出.
The thermodynamic precipitation conditions of σ-phase in 254SMo super austenitic stainless steel (SASS) and 2507 super duplex stainless steel (SDSS) were investigated by calculation using JMatPro software and experiments.Morphology and precipitation mechanism of the σ-phase in the steels after aging at different temperatures for different time were analyzed by optical microscope,scanning electron microscopy and EDS analysis.The results show that the σ-phase rich in Cr,Mo and low Ni is precipitated on the grain boundaries for the 254SMo SASS aged at 1020 ℃ for different time.With the aging time increases,the amount and size of the σ-phase increase,and it is presented short rod,strip,cellular morphology,and precipitated in accordance with the γ→σ way.The 2507 SDSS under different aging time at 950 ℃,the σ-phase rich in Cr,Mo and low Ni is precipitated on α/γ interface and the α/α grain boundaries.As the aging time increases,the amount of the σ-phase increases,and it grows into ferrite with reticular distribution in the austenitic matrix eventually,and the secondary austenite(γ2)is generated,the precipitation occurs by the α→σ + γ2 way.
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