Sigma phase formation kinetics in hyper duplex stainless steel welding filler metal
Sigma phase formation kinetics in hyper duplex stainless steel welding filler metal
复制标题
超双相不锈钢焊接填充金属中的 Sigma 相形成动力学
DOI：
10.1016/j.matchar.2023.112832
复制
发表时间：
2023
影响因子：
4.7
通讯作者：
Ramirez, Antonio J.
中科院分区：
文献类型：
--
作者：
Acuna, Andres;Ramirez, Antonio J.
这项工作提出了超双相不锈钢填充金属中西格玛相形成的动力学研究。开发并比较了两个西格玛相沉淀动力学模型。最初，使用物理模拟器进行等温热处理，持续时间为 30 秒至 600 秒，温度在 600 °C 至 1100 °C 之间，建立了实验西格玛相沉淀。在这些实验中，西格玛相的平衡体积分数在 600 秒内达到了 70%。使用实验转化数据开发了基于 CALPHAD 的动力学模型。使用基于 CALPHAD 的模型计算恒定冷却速率条件，显示 4 °C/s 的最小冷却速率作为西格玛相形成的阈值。西格玛相析出的微观结构演变遵循已知的铁素体转变为西格玛相和二次奥氏体（α→σ+γ2）的共析分解机制，其在析出时间的后期阶段演变，层状σ/γ2形态是由扩散控制的共析反应产生的。最后，我们应用 JMAK 动力学定律对实验数据集和基于 CALPHAD 的 TTT 数据集上的 sigma 相形成进行建模。在 JMAK 线性图中，发现了动力学机制的变化，从共析分解阶段转变为扩散控制生长阶段。虽然 JMAK 计算与实验数据吻合良好，但基于 CALPHAD 的数据仅在 900 °C 至 925 °C 之间的最大动力学温度附近吻合。尽管如此，使用 JMAK 方程建模的西格玛相变动力学正确地描述了描述其双动力学行为的实验数据，并在最大动力学温度范围内再现了基于 CALPHAD 的 TTT。
This work presents a kinetic study of the sigma phase formation in hyper duplex stainless steel filler metal. Two sigma phase precipitation kinetics models were developed and compared. Initially, experimental sigma phase precipitation was built using isothermal heat treatments with durations from 30 s to 600 s, and temperatures between 600 °C and 1100 °C performed using a physical simulator. In these experiments, up to 70% of the equilibrium volumetric fraction of the sigma phase was achieved in 600 s. A CALPHAD-based kinetic model was developed using the experimental transformation data. Constant cooling rate conditions were calculated using the CALPHAD-based model revealing a minimum cooling rate of 4 °C/s as the threshold for the sigma phase to form. The microstructure evolution of the sigma phase precipitation follows the known eutectoid decomposition mechanism of ferrite transformation to sigma phase and secondary austenite (α → σ + γ2), which evolved at the latter stages of the precipitation times, the lamellar σ/γ2morphology results from the eutectoid reaction, which is diffusion controlled. Finally, we applied the JMAK kinetic law to model the sigma phase formation on both datasets, the experimental and the CALPHAD-based TTTs. In the JMAK linearized plots, a kinetic mechanism change was found, switching from an eutectoid decomposition stage to a diffusion-controlled growth stage. While the JMAK calculations provided good agreement with the experimental data, the CALPHAD-based data only agreed near the maximum kinetics temperatures between 900 °C and 925 °C. Nevertheless, the sigma phase transformation kinetics modeled using JMAK equations properly described the experimental data describing its double kinetics behavior and reproduced the CALPHAD-based TTT at the maximum kinetics temperature range.