The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.
The compressive deformation behavior of as-quenched 7005 aluminum alloy was investigated at the temperature ranging from 250 °C to 450 °C and strain rate ranging from 0.0005 s-1 to 0.5 s^-1 on Gleeble-1500 thermal-simulation machine. Experimental results show that the flow stress of as-quenched 7005 alloy is affected by both deformation temperature and strain rate, which can be represented by a Zener-Hollomon parameter in an exponent-type equation. By comparing the calculated flow stress and the measured flow stress, the results show that the calculated flow stress agrees well with the experimental result. Based on a dynamic material model, the processing maps were constructed for the strains of 0.1, 0.3 and 0.5. The maps and microstructural examination revealed that the optimum hot working domain is 270-340 °C, 0.05-0.5 s^-1 with the reasonable dynamic recrystallization. The instability domain exhibits adiabatic shear bands and flow localization, which should be avoided during hot working in order to obtain satisfactory properties.
