Abstract
A submicron-grained Al-12wt% Si alloy with a uniform distribution of fine silicon particles was produced by a layer-deposition process and subsequent hot working. The grain structure was characterized by high angle grain boundaries with a random spectrum of orientation. The average sizes of both grain and silicon particle were about 0.4 μm in the as-rolled state. The grain refinement came from the dynamic recrystallization on silicon particles. The grains did not show significant growth in annealing even at 493 °C for 24 hours, whereas silicon particles grew at a remarkable rate. The coarsening phenomenon of silicon particles at elevated temperatures was studied systematically by annealing the specimens at 372 °C, 433 °C, 472 °C and 493 °C respectively for different periods. Results showed that the volume of a silicon particle increased linearly with annealing time. The activation energy for coarsening was calculated by Arrhenius equation to be 54 kcal/mole which is almost triple the activation energy for silicon diffusion in aluminum matrix. Because of the high energy value, the coarsening should not be diffusion-controlled but interface-controlled. In addition, the size distribution profile of silicon particles in aluminum matrix after annealing also accounts for the interface-controlled kinetics. © 1994.