ADI 等温淬火奥氏体组织转变的数值仿真

Numerical Simulation of Austenite Structure Transformation During ADI Austempering

中文关键词: 等温淬火球墨铸铁 (ADI)  等温转变  组织转变与碳扩散  数值仿真

英文关键词: Austempered Ductile Iron (ADI)  austempering transformation  structure transformation and carbon diffusion  numerical simulation

中文摘要:

      基于奥氏体组织转变的相场模型，结合 ADI 奥铁体中针状铁素体的特征，在相场方程的 x 和 y 方向设置不同的系数，并拟合了仿真温度下的自由能密度函数，建立了符合 ADI 奥氏体组织等温转变特征的相场模型。对 ADI 等温淬火过程中奥氏体组织转变进行了仿真分析，仿真结果表明：随着等温温度的升高，ADI 奥铁体中针状铁素体的生长速率变快，尺寸增加，长宽比减小，针状特征减弱，碳在奥铁体中的奥氏体内分布更加均匀；针状铁素体的生长进程比碳的扩散进程更快，因此，当奥氏体向奥铁体组织转变基本完成后，还需等温适当时间，使奥铁体中的奥氏体的碳充分扩散达到平衡，以获得稳定的奥铁体组织。

英文摘要:

      Based on the phase-field model of austenite structure transformation and incorporating the characteristics of acicular ferrite in ADI ausferrite, different coefficients were set in the X and Y directions of the phase-field equation. The free energy density function at simulated temperatures was fitted, establishing a phase-field model that aligns with the austempering transformation characteristics of ADI austenite structure.Numerical simulations of the austenite transformation during ADI austempering revealed that increasing the austempering temperature accelerates the growth kinetics of acicular ferrite, resulting in enlarged ferrite dimensions, reduced aspect ratios, and weakened needle-like characteristics. Concurrently, carbon distribution within the retained austenite of ausferrite became more homogeneous. The growth of acicular ferrite was found to precede carbon diffusion, necessitating a post-transformation austempering holding period to facilitate carbon equilibration in austenite, thereby stabilizing the ausferrite microstructure.