Cr. Ho et B. Cantor, HETEROGENEOUS NUCLEATION OF SOLIDIFICATION OF SI IN AL-SI AND AL-SI-PALLOYS, Acta metallurgica et materialia, 43(8), 1995, pp. 3231-3246
Citations number
17
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
Heterogeneous nucleation of solidification in melt spun Al-Si and Al-S
i-P has been studied using differential scanning calorimetry, and tran
smission, scanning transmission and high resolution electron microscop
ies. The microstructures of the heat treated melt spun alloys all cons
ist of an Al matrix, Al-Si eutectic distributed along the Al grain bou
ndaries, and Si embedded in the Al matrix. The Si microstructure depen
ds on the level of P: coarse faceted Si particles are nucleated by AlP
particles in Al-Si containing 2 ppm P and Al-Si-P containing 35 ppm P
whereas eutectic droplets of fine Si particles are nucleated by the s
urrounding Al matrix at a high undercooling in Al-Si containing 0.25 p
pm P. The Si nucleation onset temperature remains approximately consta
nt while the peak and end temperatures both decrease with increasing c
ooling rate, in agreement with classical nucleation theory. Kinetic an
alysis, using the spherical cap model gives contact angles of 10 degre
es, 43 degrees and 10 degrees for Si nucleation in low and high purity
Al-Si and Al-Si-P respectively.