TY - JOUR
T1 - Transition from hypereutectic to hypoeutectic for rapid solidification in an undercooled Co-B alloy
AU - He, Yixuan
AU - Li, Jinshan
AU - Wang, Jun
AU - Beaugnon, Eric
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/10/1
Y1 - 2018/10/1
N2 - Phase selection, a common and important phenomenon in rapid solidification, determines the solidification sequence and the mechanical/physical properties. In this work, a Co-20 at%B hypereutectic alloy was undercooled by the melt fluxing technique and the microstructure was characterized by the back-scattering diffraction technique. A transition from hypereutectic to hypoeutectic was found at a critical undercooling of ΔT = 119 K. When ΔT < 119 K, a primary directional dendritic β-Co3B phase surrounded by the regular α-Co + β-Co3B lamellar eutectics was found. When ΔT > 119 K, the above hypereutectic microstructure changes into hypoeutectic structure with the α-Co phase as the primary phase. According to dendrite growth model, the transition from hypereutectic to hypoeutectic can be ascribed to the higher growth velocity of the α-Co phase than the β-Co3B phase, i.e., the growth-controlled mechanism. The current work shows also that there is a coupled zone skewed to the β-Co3B phase in the Co-B alloys system.
AB - Phase selection, a common and important phenomenon in rapid solidification, determines the solidification sequence and the mechanical/physical properties. In this work, a Co-20 at%B hypereutectic alloy was undercooled by the melt fluxing technique and the microstructure was characterized by the back-scattering diffraction technique. A transition from hypereutectic to hypoeutectic was found at a critical undercooling of ΔT = 119 K. When ΔT < 119 K, a primary directional dendritic β-Co3B phase surrounded by the regular α-Co + β-Co3B lamellar eutectics was found. When ΔT > 119 K, the above hypereutectic microstructure changes into hypoeutectic structure with the α-Co phase as the primary phase. According to dendrite growth model, the transition from hypereutectic to hypoeutectic can be ascribed to the higher growth velocity of the α-Co phase than the β-Co3B phase, i.e., the growth-controlled mechanism. The current work shows also that there is a coupled zone skewed to the β-Co3B phase in the Co-B alloys system.
KW - A1. Eutectics
KW - A1. Solidification
KW - A2. Growth from melt
KW - B1. Alloys
UR - http://www.scopus.com/inward/record.url?scp=85051146808&partnerID=8YFLogxK
U2 - 10.1016/j.jcrysgro.2018.07.032
DO - 10.1016/j.jcrysgro.2018.07.032
M3 - 文章
AN - SCOPUS:85051146808
SN - 0022-0248
VL - 499
SP - 98
EP - 105
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
ER -