MICROSTRUCTURE AND PROPERTIES OF SPRAY-DEPOSITED 2014-VOL PCT SIC PARTICULATE-REINFORCED METAL-MATRIX COMPOSITE(15)

A metal matrix composite (MMC) of 2014 aluminum alloy reinforced with 15 vol pct SiC particulate was produced by the spray-forming-depositio n process. The as-deposited preform revealed a high density and a homo geneous reinforcement distribution. Reactive products were not found o n interfaces between the reinforcement and the matrix. Compared to the control alloy, the composite showed accelerated aging after solutioni zing at 502 degrees C, while aging was retarded after solutionizing at 475 degrees C, Analysis indicated that the activation energy was almo st the same for the aging process after different solutionizing treatm ents. This suggested that while the thermal barrier for the aging proc ess was the same, other factors affecting the aging process should be considered. For example, the effective concentration of the precipitat e forming elements possibly decreased after incompletely solutionizing at 475 degrees C. After heat treatment, the composite showed a tensil e strength similar to the control alloy. The wear resistance of the co mposite improved considerably. The aging behavior of the composite was also studied using the nanoindentation technique. Steep gradient dist ribution of elastic modulus and hardness around the reinforcement SiC particulate was observed. Theoretical analysis showed that this could be attributed to the gradient distribution of precipitates, resulting from a gradient distribution of dislocation density around the SiC par ticulates caused by residual thermal misfit stresses.