SA508-3钢粗大非平衡组织重新加热奥氏体晶核形成与长大行为

Formation and growth behavior of austenite nuclei in coarse and non-equilibrium structure of SA508-3 steel during reheating

以SA508-3钢为研究对象,将其粗大非平衡组织在700~1000℃范围重新加热奥氏体化,利用光学显微镜分析其奥氏体晶核形成与长大行为。结果表明：SA508-3钢粗大非平衡组织重新加热奥氏体化过程中,γ晶核优先在原奥氏体晶界球状形成并长大,在晶内α相板条束界也有少许针状晶核形成。在较低温度（Ac1~760℃）时,γ晶核均有取向性的合并长大趋势,α相板条束界γ晶核长大呈长岛状,原奥氏体晶界γ晶核长大呈长条状。随着温度升高（760℃~Ac3）,新的球状γ晶核不断在原奥氏体晶粒内未奥氏体化区域内产生,新形成的球状γ晶核均以等轴方式长大,逐渐长大成细小的等轴晶粒。当温度升高到Ac3＋150℃时,奥氏体晶粒呈细小等轴状,继续升高至1000℃时,奥氏体晶粒粗化。

Coarse and non-equilibrium structure of SA508-3 steel was reheated and austenitized in the range of 700-1000 ℃,and the austenite nucleation and growth behavior were analyzed by optical microscope.The results show that spherical γ nuclei are preferentially formed and grown in prior austenite grain boundary and articulate γ nuclei formed in prior α-phase plate bundle boundary during reheating austenitizing process.At lower temperature（ Ac1-760 ℃）,γ nuclei have the tendency to merger grow up.The acicular γ nuclei in the αphase plate boundary grow into long island shape and the spherical γ nuclei in prior austenite boundary grow into long stripe shape.With the increase of temperature（ 760 ℃-Ac3）,the new spherical γ nuclei are formed internally inside the region of non-austenitized inside the original austenite grains.The new γ nuclei grow in equiaxed manner and gradually grew into small equiaxed grains.When the temperature increased to Ac3＋ 150 ℃,the austenite grains are small equiaxed; while continue to rise to 1000 ℃,the austenite grain has been coarsened.