Abstract:The microstructural evolution and growth mechanism of the melt spun Al-In monotectic alloy were studied. During the rapid solidification of Al-17.5%In, a cellular structure→equiaxed structure transition occurs through the ribbon thickness. The as-solidified microstructures are characterized by a homogeneous distribution of nanometer sized indium particles embedded within the matrix. However, with increasing distance from the chilled surface, the average particle size increases. In the underside of the ribbon, some particle arrays are perpendicular to the growth front. Next, all of the indium particles distribute randomly within the matrix. In the upside of the ribbon, some bigger indium particles distribute along the equiaxed grain boundaries. The diameter distributions of indium particles within Al matrix are bimodal. Compared with the massive partitionless solidification, the liquid separation process is the prevailing process during the nonequilibrium solidification. The cooling rate, the interface energies (γ_S1/L1,γ_S1/L2 and γ_L1/L2) and the growth mechanism all have effects on the microstructure.

Key words: Al-In immiscible alloy;  rapid solidification; microstructure