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利用共焦激光扫描显微镜原位观察了AISI304不锈钢冷却过程中高温铁素体(δ)→奥氏体(→)相变的过程及其特征．结果表明,γ相优先在δ晶界处形成；冷却速率影响γ相的生长形态,典型形态分为块状、圆形、树枝状等；“游离”γ枝晶发生粗化,并和周围的γ枝晶聚合；相同冷却条件下,δ晶界处的γ枝晶聚合程度明显高于δ晶粒内部；二次枝晶在冷却过程中粗化,并竞争生长．利用ThermoCalc计算C元素在δ→γ相变过程中的偏析系数,以此求解δ→γ相变数学模型．
The process and characteristics of high temperature ferrite (δ) → austenite (→) phase transformation during AISI 304 stainless steel cooling were observed by confocal laser scanning microscopy. The results show that the γ phase is preferentially formed at the δ grain boundary. The cooling rate affects the growth morphology of the γ phase. The typical morphology is divided into blocks, circles and dendrites. The “free” γ dendrite coarsens and coalesces with the surrounding γ dendrites. Under the same cooling conditions, the degree of γ dendrite polymerization at δ grain boundaries was significantly higher than that of δ grains. The secondary dendrites coarsen during cooling and competed for growth. Using ThermoCalc to calculate the segregation coefficient of C element in the δ → γ transformation process, the mathematical model of δ → γ transformation is solved.