The control of grain size and distribution of particles in a (6061 alloy)(m)/(Al2O3)(p) composite by solutionizing treatment

The grain growth during an isothermal treatment at a solutionizing temperature of 540 degrees C has been studied in a composite containing 6061 aluminum alloy matrix with Al2O3 particles. The grain growth law is generally applicable to the composites containing 0.10, 0.15, and 0.20 volume fraction of the Al2O3 particles (VFAP). It has been observed that the grain growth process involves the disintegration of the agglomerated particles first and then particles coalesce at longer solutionizing times in the composite containing 0.20 VFAP. The process of coalescence has not been observed up to a heating time of 20 hours at this temperature in the composites containing 0.10 and 0.15 VFAP. The transmission electron microscopy (TEM) study indicates the generation of a large number of dislocations in both the matrix and the area adjacent to the particles. The dislocation densities at these two locations in the composites increase with an increase in VFAP and the particle size. The microhardness measurements confirm the microstructural observations, and the hardness values for the composite and the matrix appear to be more sensitive to the particle distribution and the particle size compared to the grain size.