Evidence of austenite by-passing in a stainless steel obtained from laser melting additive manufacturing
Evidence of austenite by-passing in a stainless steel obtained from laser melting additive manufacturing
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DOI：
10.1016/j.addma.2018.11.004
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发表时间：
2019-01-01
影响因子：
11
通讯作者：
Bosch, Cedric
中科院分区：
文献类型：
--
作者：
Alnajjar, Michella;Christien, Frederic;Bosch, Cedric
对氩气氛中采用选择性激光熔化（SLM）工艺制备的AISI 17-4 PH不锈钢进行了显微组织表征。通常，这种钢表现出马氏体结构，具有小部分的δ铁素体。然而，X射线衍射和电子背散射衍射（EBSD）的综合结果证明，SLM-ed 17-4 PH钢具有完全铁素体显微组织，更具体地说是δ铁素体。显微组织由沿着成型方向伸长的粗铁素体晶粒组成，具有明显的凝固晶体学织构。这些结果与整个SLM过程中经历的高冷却和加热速率相关，该过程抑制奥氏体形成并在许多热循环期间产生该相的“旁路”现象。此外，能量色散X射线光谱（EDS）的测量显示，没有任何树枝状结构的元素的均匀分布。极高的冷却动力学诱导无扩散固化，导致均匀的元素组成。还发现，铁素体SLM化的材料可以通过在1050摄氏度下再结晶化然后淬火而再次转变为马氏体。
Microstructural characterization was carried out on AISI 17-4 PH stainless steel fabricated by selective laser melting (SLM) in an argon environment. Conventionally, this steel exhibits a martensitic structure with a small fraction of delta ferrite. However, the combined findings of x-ray diffraction and electron backscatter diffraction (EBSD) proved that SLM-ed 17-4 PH steel has a fully ferritic microstructure, more specifically delta ferrite. The microstructure consists of coarse ferritic grains elongated along the build direction, with a pronounced solidification crystallographic texture. These results were associated to the high cooling and heating rates experienced throughout the SLM process that suppressed the austenite formation and produced a "by-passing" phenomenon of this phase during the numerous thermal cycles. Furthermore, the energy-dispersive X-ray spectroscopy (EDS) measurements revealed a uniform distribution of elements without any dendritic structure. The extremely high cooling kinetics induced a diffusionless solidification, resulting in a homogeneous elemental composition. It was also found that the ferritic SLM-ed material can be transformed to martensite again by re-austenitization at 1050 degrees C followed by quenching.