Effects of reinforcement with potassium hexatitanate short fiber on machinability of aluminum alloy

Abstract

The effects of reinforcement with the potassium hexatitanate short fiber on the machinability of the alloy under various cutting conditions were investigated. JIS-AC8A alloy was used as the matrix metal, and two kinds of potassium hexatitanate short fibers were used as the reinforcements. The composites were fabricated by squeeze casting. The machinability of the composites was compared with that of the composites reinforced with various reinforcements such as potassium titanate whisker and aluminum borate whisker. The reinforcements were randomly arranged in the alloy matrix, and no agglomeration of the reinforcements or porosity was observed, indicating that the melt infiltration into the reinforcement preform was perfectly accomplished. The cutting force and feed force of the alloy was reduced by the reinforcement. These force values when the potassium hexatitanate short fiber-reinforced composite was machined was smaller than that when the composites with other reinforcements were machined. The roughness of the machined surface of the alloy drastically decreased by the reinforcement under every cutting condition, and the surface roughness of composites was close to the theoretical roughness. The difference in roughness values between the composites was small. From the surface roughness values, the observation of the chip formation in the cutting process and the observation of machined surface, we have concluded that the reinforcements in the composite suppress the formation of the built-up edge during the cutting process. The machined surfaces and chip forms indicated that the reinforcements in the composite facilitated the shear deformation of the chips because the fibers were easily sheared by the cutting. The tool life when the potassium hexatitanate short fiber-reinforced composite was machined was significantly longer than that of aluminum borate whisker-reinforced composite.

Keywords

• metal matrix composite
• aluminum
• potassium titanate fiber
• whisker
• squeeze casting
• microstructure
• machinability
• cutting resistance
• surface roughness
• tool wear