Effects of Growth Rates and Compositions on Dendrite Arm Spacings in Directionally Solidified Al-Zn Alloys


ACER E., Cadirli E. , Erol H., KAYA H. , GÜNDÜZ M.

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ss.5911-5923, 2017 (SCI İndekslerine Giren Dergi) identifier identifier

  • Basım Tarihi: 2017
  • Doi Numarası: 10.1007/s11661-017-4337-x
  • Dergi Adı: METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
  • Sayfa Sayıları: ss.5911-5923

Özet

Dendritic spacing can affect microsegregation profiles and also the formation of secondary phases within interdendritic regions, which influences the mechanical properties of cast structures. To understand dendritic spacings, it is important to understand the effects of growth rate and composition on primary dendrite arm spacing (lambda(1)) and secondary dendrite arm spacing (lambda(2)). In this study, aluminum alloys with concentrations of (1, 3, and 5 wt pct) Zn were directionally solidified upwards using a Bridgman-type directional solidification apparatus under a constant temperature gradient (10.3 K/mm), resulting in a wide range of growth rates (8.3-165.0 mu m/s). Microstructural parameters, lambda(1) and lambda(2) were measured and expressed as functions of growth rate and composition using a linear regression analysis method. The values of lambda(1) and lambda(2) decreased with increasing growth rates. However, the values of lambda(1) increased with increasing concentration of Zn in the Al-Zn alloy, but the values of lambda(2) decreased systematically with an increased Zn concentration. In addition, a transition from a cellular to a dendritic structure was observed at a relatively low growth rate (16.5 mu m/s) in this study of binary alloys. The experimental results were compared with predictive theoretical models as well as experimental works for dendritic spacing. (C) The Minerals, Metals & Materials Society and ASM International 2017