Microstructures of rapidly solidified Al-In immiscible alloys

Homogeneous Al-In immiscible alloys were fabricated by melt spinning rapid solidification technique and their microstructures were investigated. The as-solidified microstructures are characterized by a homogeneous distribution of very fine In particles embedded within Al matrix. The In particle size increases with increasing distance from the chilled surface along the thickness direction of Al-In ribbons. Under the same wheel speed (same cooling rate), the In particles' average size increases with rising contents of In. Under the same composition, the In particles' average size decreases with increasing wheel speed; Brownian collision and the convection in the puddle are the major factors influencing the coarsening process of the second phase droplets during melt spinning process. The size distribution of In particles within Al matrix is bimodal, the bigger particles are formed during cooling through the region of liquid immiscibility while the smaller particles are formed during monotectic reaction.