The effects of stored energy on wear resistance of friction stir processed pure Ti

The friction stir processed pure Ti was annealed at 550 °C with various annealing times. Dry sliding wear tests on friction stir processed and as-annealed pure Ti were performed at room temperature. Friction coefficient and wear rate of the alloys were measured. The results showed that the friction stir processed pure Ti with high hardness revealed lower wear resistance than as-annealed samples. The stored energy of the samples before and after annealing treatment were calculated. The relationship between work hardening and wear resistance of pure Ti was discussed. The run-in period increased as the stored energy in the pure Ti decreased. The fine-grained pure Ti with 400 kJ/m3 low angle grain boundaries stored energy exhibited the lowest wear rate. The wear mechanism of fine-grained pure Ti changed from fatigue wear and abrasive wear to adhesive wear after annealing treatment. Keywords: Titanium alloy, Friction stir processing, Annealing, Stored energy, Wear resistanc

Localised corrosion in AA 2099-T83 aluminium-lithium alloy:the role of grain orientation

AbstractThe mechanism for localised corrosion in AA 2099-T83 alloy during immersion in 3.5% NaCl solution is investigated. It is found that localised corrosion tends to occur in the grain with relatively large Schmid factor. The localised corrosion is related to selective dissolution of T1 (Al2CuLi) phase that preferentially precipitates at grain/subgrain boundaries and dislocations within grain interiors. A model is proposed to explain the development of the localised corrosion in the alloy by taking into account heterogeneous plastic deformation during cold working and preferential precipitation of T1 phase at crystallographic defects within deformed grains