Evidence that the liquid structure affects the nucleation of the primary metastable L12-Al3Zr in additive manufacturing

• Published in: Scripta materialia Vol. 226; p. 115212
• Main Authors: Buttard, Maxence, Martin, Guilhem, Harrison, Patrick, Rauch, Edgar F., Chéhab, Béchir, Jarry, Philippe, Blandin, Jean-Jacques, Donnadieu, Patricia
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.03.2023; Elsevier
• Subjects: Additive manufacturing; Al alloys; Engineering Sciences; ISRO; Materials; Nucleation; Primary phase; Primary phase; Nucleation; Additive manufacturing; Al alloys; ISRO; Additive manufacturing Nucleation Al alloys ISRO Primary phase
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/j.scriptamat.2022.115212

The strategy aiming at promoting the precipitation of the primary metastable L12-Al3X phase is the most widely used to refine grain size in Al alloys designed for additive manufacturing. It is generally admitted that Al grains nucleate onto the primary L12-Al3X precipitates by epitaxy resulting in a cube-cube orientation relationship. Here we report TEM observations showing clusters of precipitates of this primary L12-Al3X phase. Using Automated Crystallographic Orientation Mapping in the TEM, we show that such clusters consist of various orientations. Analysis of those clusters reveals that some orientations share common 5-fold rotational symmetry axes suggesting that they have nucleated from an icosahedral template. We conclude that Icosahedral Short Range Order (ISRO) in the liquid can play a role in the nucleation of the primary metastable L12-Al3Zr phase through the ISRO-mediated nucleation mechanism. [Display omitted]