Growth of Solidification Grain of Aluminum Alloy Near a Mold

Hisao Esaka; Yoshimasa Kataoka; Kei Shinozuka

doi:10.4028/www.scientific.net/MSF.828-829.69

Paper Titles

Direct-Chill Casting of AA7449 Aerospace Alloy under Electromagnetic and Ultrasonic Combined Fields
p.48

Effect of Al-5Ti-1B Grain Refiner Addition on the Formation of Intermetallic Compounds in Al-Mg-Si-Mn-Fe Alloys
p.53

Effect of Solidified Structure on Hot Tearing in Al-Cu Alloy
p.58

Form Accuracy of Optical Mould Inserts Made from Rapidly Solidified Aluminium Alloys
p.62

Growth of Solidification Grain of Aluminum Alloy Near a Mold
p.69

Influence of Supercooling on the Formation of Primary Phase during Solidification
p.73

Magnesium Melt Protection
p.78

Melt Refining Technology of Highly-Contaminated Magnesium Alloy Scraps via a Sequential Refining Process
p.82

Microstructure and Texture Development during Melt Conditioned Twin Roll Casting and Downstream Processing in an AZ31 Magnesium Alloy
p.87

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Growth of Solidification Grain of Aluminum Alloy Near a Mold

Abstract:

Surface quality as well as internal quality of cast products of aluminum alloys are strongly affected by the process of initial solidification. Control of solidified structure in this region is therefore quite important. In order to understand the growth of solidified grain, crystallographic characterization has been performed using EBSD (Electron Backscattered Diffraction) in this study. Al-6 mass%Si alloy was cast at 750°C on the chill plate. Longitudinal cross section of solidified shell was analyzed. In the region of initial solidification, many small crystals nucleated on the mold surface. The crystallographic orientations of these grains were random. It is normally found that an unfavorable grain was eliminated by a favorable grain. However, occasionally, we have found that an unfavorable grain enlarged its size. In this case, dendrite, the growth direction of which was far from the heat flow direction, gradually changed its crystallographic orientation from unfavorable one to favorable one. The grain enlarged its size by multiplication of dendrite arms. Crystallographic orientation of dendrite changed little by little when it branched. This kind of phenomena may take place in unsteady condition, such as initial solidification region.