Numerický model krystalizace čistého hliníku

A Numerical Model of the Crystallization of Pure Aluminium

článek ve sborníku ve WoS nebo Scopus

en

The character of primary crystallization was investigated on a simple cylindrical sample, crystallizing in a cast-iron mould pre-heated to various temperatures. The experimental research comprised the measurement of temperatures using thermocouples, the evaluation of the experimentally acquired temperature gradients G, and the shift rate of the phase transition interface R. Furthermore, it comprised the determination of the so-called critical values Gcr and Rcr, which are reached by the crystallizing metal in the transition interface where the columnar crystals transform into the equiaxed. The numerical model had been developed to expand the limited experimental capabilities of the evaluation of G and R to every point of the longitudinal section, based on the investigation of the 3D transient temperature field within the system comprising the casting, the mould and ambient. Furthermore, the authors have discovered a new criterion (called the 'temperature-delay' criterion), which predicts the macro-structure. This criterion can not only determine the position of the transition interface between both crystallizations, but also the time in which one transforms into the other.

Tento příspěvek se zabývá studiem povahy primární krystalizace jednoduchého válcovitého vzorku, který krystalizuje v litinové formě předehřáté na různé teploty. Experimenty zahrnují měření teplot termočlánkem, zhodnocení gradientů teploty G a hodnotu posunu mezifázového rozhraní R. Navíc obsahuje kritické hodnoty Gcr a Rcr, kterých bylo dosaženo při krystalizaci kovu při přeměně ze sloupcovitých krystalů na rovnoosé. Byl navržen numerický model, který rozšiřuje omezené experimentální možnosti hodnocení G a R ke každému bodu v podélné oblasti, založený na 3D modelu přechodového teplotního pole formy a jejího okolí. Dále autoři vyvinuli nové kritérium (zvané teplotně zpožděné – posun), které predikuje makrostrukturu.

The character of primary crystallization was investigated on a simple cylindrical sample, crystallizing in a cast-iron mould pre-heated to various temperatures. The experimental research comprised the measurement of temperatures using thermocouples, the evaluation of the experimentally acquired temperature gradients G, and the shift rate of the phase transition interface R. Furthermore, it comprised the determination of the so-called critical values Gcr and Rcr, which are reached by the crystallizing metal in the transition interface where the columnar crystals transform into the equiaxed. The numerical model had been developed to expand the limited experimental capabilities of the evaluation of G and R to every point of the longitudinal section, based on the investigation of the 3D transient temperature field within the system comprising the casting, the mould and ambient. Furthermore, the authors have discovered a new criterion (called the 'temperature-delay' criterion), which predicts the macro-structure. This criterion can not only determine the position of the transition interface between both crystallizations, but also the time in which one transforms into the other.

crystallization, temperature field, numerical model, macro-structure

2006

01.05.2006

Tanger Ostrava,

Tanger Ostrava, Keltičkova 62, 710 00 Ostrava

80-86840-18-2

Metal 2006

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