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Phase-transformation and precipitation kinetics in vanadium micro-alloyed steels by in-situ, simultaneous neutron diffraction and SANS
Acta Materialia ( IF 9.4 ) Pub Date : 2021-09-17 , DOI: 10.1016/j.actamat.2021.117317
Chrysoula Ioannidou 1 , Alfonso Navarro-López 1 , Robert M. Dalgliesh 2 , Arjan Rijkenberg 3 , Xukai Zhang 4 , Bart Kooi 4 , Nico Geerlofs 1 , Catherine Pappas 5 , Jilt Sietsma 1 , Ad A. van Well 5 , S. Erik Offerman 1
Affiliation  

In-situ Neutron Diffraction and Small-Angle Neutron Scattering (SANS) are employed for the first time simultaneously in order to reveal the interaction between the austenite to ferrite phase transformation and the precipitation kinetics during isothermal annealing at 650 and at 700 °C in three steels with different vanadium (V) and carbon (C) concentrations. Austenite-to-ferrite phase transformation is observed in all three steels at both temperatures. The phase transformation is completed during a 10 h annealing treatment in all cases. The phase transformation is faster at 650 than at 700 °C for all alloys. Additions of vanadium and carbon to the steel composition cause a retardation of the phase transformation. The effect of each element is explained through its contribution to the Gibbs free energy dissipation. The austenite-to-ferrite phase transformation is found to initiate the vanadium carbide precipitation. Larger and fewer precipitates are detected at 700 than at 650 °C in all three steels, and a larger number density of precipitates is detected in the steel with higher concentrations of vanadium and carbon. After 10 h of annealing, the precipitated phase does not reach the equilibrium fraction as calculated by ThermoCalc. The external magnetic field applied during the experiments, necessary for the SANS measurements, causes a delay in the onset and time evolution of the austenite-to-ferrite phase transformation and consequently on the precipitation kinetics.



中文翻译:

通过原位、同步中子衍射和 SANS 研究钒微合金钢的相变和析出动力学

首次同时采用原位中子衍射和小角中子散射 (SANS) 以揭示奥氏体到铁素体相变与 650 和 700 °C 等温退火过程中三个过程中析出动力学之间的相互作用。含不同钒 ( V ) 和碳 ( C ) 的钢) 浓度。在两种温度下,在所有三种钢中都观察到奥氏体到铁素体的相变。在所有情况下,相变都在 10 小时的退火处理期间完成。所有合金在 650°C 时的相变比在 700°C 时更快。向钢成分中添加钒和碳会导致相变延迟。每个元素的影响通过其对吉布斯自由能耗散的贡献来解释。发现奥氏体到铁素体相变引发碳化钒沉淀。与 650 °C 相比,所有三种钢在 700°C 时检测到的沉淀物数量越来越少,并且在钒和碳浓度较高的钢中检测到的沉淀物数量密度更大。退火 10 小时后,沉淀相未达到 ThermoCalc 计算的平衡分数。SANS 测量所必需的实验期间施加的外部磁场会导致奥氏体到铁素体相变的开始和时间演变延迟,从而导致沉淀动力学延迟。

更新日期:2021-09-27
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