کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1583780 1514897 2007 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Suppression of crystallization during high velocity impact quenching of alumina droplets: Observations and characterization
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد دانش مواد (عمومی)
پیش نمایش صفحه اول مقاله
Suppression of crystallization during high velocity impact quenching of alumina droplets: Observations and characterization
چکیده انگلیسی

Droplets of alumina were deposited and quenched onto various smooth substrates using the high-velocity oxy-fuel (HVOF) thermal spray process. The microstructure of single splats was examined using optical microscopy, atomic force microscopy (AFM), focused ion beam assisted scanning electron microscopy (FIB-SEM), and transmission electron microscopy (TEM). It was found that the high impact velocity inherent in HVOF formed splats that were in intimate contact with the substrate, leading to a high solidification rate up to 1010 K/s. The solidified alumina splats exhibited a smooth surface devoid of “mud-crack” networks of surface micro-cracking, commonly observed in ceramic plasma sprayed systems. Microstructural examinations of the smooth areas of the splat revealed an amorphous microstructure as confirmed by selected area electron diffraction. In local areas of poor contact between the splat and substrate, a polycrystalline microstructure was discernible and a metastable γ-Al2O3 phase was detected. Second layer splats, that landed on top of a first layer splat and experienced slower cooling rate, were found to have surface cracking, and revealed principally a γ-Al2O3 nano-crystalline structure. The observation of amorphous alumina is explained by the suppression of a first order liquid-to-solid phase transformation, due to a high solidification rate that we estimate.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Materials Science and Engineering: A - Volume 456, Issues 1–2, 15 May 2007, Pages 35–42
نویسندگان
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