Effect of cryomilling on matrix/reinforcement interfaces and properties of Al-TiB2 composites

Abstract

The present study reports the effects of cryomilling on the microstructural and mechanical properties of pressurelessly sintered Al-xTiB(2) (x=5, 10, or 15 wt%) composites. Composite powders milled under cryogenic conditions in the presence of liquid nitrogen were compacted in a hydraulic press, and the compacts were pressurelessly sintered at 650 degrees C for 5 h under Ar/H-2 gas. The effects of cryomilling time (10 or 20 min) and TiB2 content (5, 10, or 15 wt%) on the microstructures, densities, and mechanical properties (wear characteristics, hardness, elastic modulus, indentation response) of the sintered products were investigated. Because the milling process was under cryogenic conditions, the formation of intermetallic phases between the matrix and reinforcement particles, such as Al3Ti, was not observed at the interfaces of the sintered Al-TiB2 composites, even when 15 wt% TiB2 was used. Cryomilling for 10 min followed by pressureless sintering of Al matrix composites reinforced with 5-15 wt% TiB2 particles resulted in bulk samples with relative densities of 97.38-98.43%, hardness values of 0.75-1.35 GPa, wear volume losses of 0.276-1.265 mm(3), and elastic moduli of 283-433.7 GPa.