Functionally graded stainless steels with tailored grain boundary serration
Functionally graded stainless steels with tailored grain boundary serration
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DOI：
10.1016/j.scriptamat.2023.115714
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发表时间：
2023
影响因子：
6
通讯作者：
Y. Nie;Y.T. Chang;M. Charpagne
中科院分区：
文献类型：
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作者：
Y. Nie;Y.T. Chang;M. Charpagne
我们展示了在定向能量沉积增材制造过程中，通过在飞行中合金化粉末混合物来空间控制功能梯度不锈钢中晶界锯齿程度的可能性。晶界锯齿是多晶微结构中的一个有吸引力的特征，因为它赋予对裂纹扩展和热腐蚀的上级抵抗性。在微观结构尺度上的定量测量加上热力学计算，使我们能够提出一种机制来解释晶界锯齿的起源。由Cr/Ni比控制的在凝固期间瞬时δ铁素体的形成及其随后在冷却期间的溶解导致残余铁素体颗粒的形成，残余铁素体颗粒通过Smith-Zener钉扎现象阻碍固态奥氏体晶粒的生长。这一发现为增材制造过程中的原位晶界工程开辟了新的前景。
We demonstrate the possibility of spatially controlling the degree of grain boundary serration in functionally graded stainless steels, by alloying powder mixtures on-the-fly during directed energy deposition additive manufacturing. Grain boundary serration is an attractive feature in polycrystalline microstructures, as it confers superior resistance to crack propagation and hot corrosion. Quantitative measurements at the microstructure scale coupled with thermodynamic calculations allow us to propose a mechanism to explain the origin of grain boundary serration. The formation of transient δ ferrite during solidification and its subsequent dissolution during cooling, governed by the Cr/Ni ratio, leads to the formation of remnant ferrite particles that hinder the growth of austenite grains in the solid state via a Smith-Zener pinning phenomenon. This finding opens new perspectives for grain boundary engineering, in-situ during additive manufacturing.