Microstructure and fatigue characteristics of direct chill cast and electromagnetic cast 2024 Al alloy ingots |
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Authors: | Sug Won Kim Hai Hao |
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Affiliation: | (1) School of New Materials Engineering, RCIT, Engineering Research Institute, the Chonbuk National University, 561-756 Chonbuk, South Korea;(2) Research Institute of Advanced Materials Development (RIAMD), the Chonbuk National University, 561-756 Chonbuk, South Korea |
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Abstract: | The distinct advantages of the electromagnetic casting (EMC) process consist in the presence of stirring motions in the melt,
which lead to significant grain size reduction in solidified ingot. Furthermore, surface and subsurface qualities are improved
due to the absence of ingot mold. However, it is impossible to achieve the aforementioned advantages in conventional direct
chill casting (DCC). In order to contrast the before and after heat treatments of the microstructural and mechanical characteristics
of EMC and DCC 2024 aluminium alloys, optical microscopy, scanning electron microscopy, transmission electron microscopy (TEM),
X-ray diffractions (XRD), differential scanning calorimetry (DSC), etc. were carried out. Compared with the DCC ingot, the EMC ingot has better mechanical properties not only in the ascast condition
but also in the as-aged condition. The DSC curves show that the EMC specimens have high enthalpy, i.e., the thermal kinetic
energy to form precipitates during the aging treatment process. Despite heat treatments applied to the DCC ingot, it fails
to attain the same mechanical properties as the EMC ingot. Moreover, considering the expernsive scalping operation for DCC
ingots, the EMC technique, which offers a lower manufacturing cost, is one of the best manufacturing methods used in obtaining
the ingots of wrought aluminum alloys. |
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