{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T01:15:25Z","timestamp":1777943725424,"version":"3.51.4"},"reference-count":39,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2025,3,28]],"date-time":"2025-03-28T00:00:00Z","timestamp":1743120000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Shenzhen Science and Technology Program","award":["JSGG20220831092800001"],"award-info":[{"award-number":["JSGG20220831092800001"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Solidification experiments in two opposite directions were conducted to investigate the buoyancy effect on freckle formation during directional solidification in single-crystal superalloy castings. During conventional upward solidification with the superalloy CMSX-4, severe freckles were observed in castings of various geometries. By reversing the solidification direction from upward to downward, freckle-free castings could be obtained. To visually verify the effect of the solidification direction, an in situ observation experiment by varying the solidification direction was performed using a Ga-In alloy. In the upward solidification process, strong solutal convection was visually observed due to the decrease in the density of the interdendritic liquid. Conversely, a stable condition without visible flow was established during downward solidification, due to the stable state of the top-light, bottom-heavy liquid system. A new Rayleigh-number model was successfully applied to characterize the freckle features in superalloy cluster castings. When the solidification direction was reversed from upward to downward, the driving force for solutal convection was suppressed, leading to the complete elimination of freckle formation in single-crystal superalloy castings.<\/jats:p>","DOI":"10.3390\/ma18071534","type":"journal-article","created":{"date-parts":[[2025,3,28]],"date-time":"2025-03-28T13:36:49Z","timestamp":1743169009000},"page":"1534","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Effect of Solidification Direction on the Freckle Formation in Single-Crystal Superalloy Castings"],"prefix":"10.3390","volume":"18","author":[{"given":"Dexin","family":"Ma","sequence":"first","affiliation":[{"name":"State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China"},{"name":"Wedge Central South Research Institute, Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hongyuan","family":"Sun","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China"},{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yunxing","family":"Zhao","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China"},{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Weitai","family":"Xu","sequence":"additional","affiliation":[{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zaiwang","family":"Huang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bowen","family":"Cheng","sequence":"additional","affiliation":[{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0749-7430","authenticated-orcid":false,"given":"Yang","family":"Liu","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Manufacturing System Engineering, Xi\u2019an Jiaotong University, Xi\u2019an 710049, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fu","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Manufacturing System Engineering, Xi\u2019an Jiaotong University, Xi\u2019an 710049, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qiang","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Manufacturing System Engineering, Xi\u2019an Jiaotong University, Xi\u2019an 710049, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lv","family":"Li","sequence":"additional","affiliation":[{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yangpi","family":"Deng","sequence":"additional","affiliation":[{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fuze","family":"Xu","sequence":"additional","affiliation":[{"name":"Shenzhen Wedge Aviation Technology Co., Ltd., Shenzhen 518045, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2489-1971","authenticated-orcid":false,"given":"Haijie","family":"Zhang","sequence":"additional","affiliation":[{"name":"Chair for Simulation and Modelling of Metallurgy Processes, Department of Metallurgy, University of Leoben, 8700 Leoben, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0321-412X","authenticated-orcid":false,"given":"Menghuai","family":"Wu","sequence":"additional","affiliation":[{"name":"Chair for Simulation and Modelling of Metallurgy Processes, Department of Metallurgy, University of Leoben, 8700 Leoben, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,3,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Meetham, G.W. 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