| The microstructure of rapidly solidified Al-Cr alloys was investigated by scanning transmission electron microscopy (STEM), X-ray diffraction and micro-Victors hardness test. The temperature mariation during rapid solidification was studied to interpret the results. From the thermal analysis, the relationship between the cooling rate and the dendritic cell size was found to correspond to a previous theory which was obtained from an extrapolation of the measurements at slow cooling rate. The relatinship between the growth rate and the dendritic ceil size, however, was shown to be lower than those of general Al alloys, because the rate of the primary phase formation was suppressed by the increased fooling rate. By detailed composition measurements, the possible solubilily range of the complete supersaturation was found to be 3.43 wt% Cr. Above this concentration, the microstructure changed to a cellular structure by recoalescence in the last stage of solidification. |
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