This paper presents an overview of the corrosion behavior of titanium (Ti) alloys in both acidic and saline solutions. The solutions covered in this review are essentially the typical electrolytes encountered by Ti alloys when applied under service conditions. Although Ti alloys are generally known to be corrosion resistant, this review identifies strong reducing acids and fluoride-containing solutions as electrolytes that corrode Ti and its alloys. The pathways that the knowledge of the corrosion behavior of Ti alloys have followed from the 1950s to date are captured in this review. Based on this, the different factors influencing the corrosion behavior of Ti alloys are highlighted and the different research concepts for improving the corrosion resistance of Ti alloys in both solutions are discussed. The limitations of these research concepts are mentioned and the directions for future research are proposed.

The influence of annealing on the microstructure, mechanical and sliding wear characteristics of Ni-based alloys produced by spark plasma sintering (SPS) was investigated. As-sintered alloys had a lamellar-like microstructure consisting of (γ')-FeNi3 and γ-(NiFe) phases, with the γ' precipitates interconnected by narrow channels of γ phases at the interfaces. Lower Co contents (i.e. 30, 35 wt%) led to the formations of poorly bonded coarse γ precipitate islands. Annealed Ni-5Fe-45Co alloy exhibited the most excellent wear performance with the lowest coefficients of friction (0.142±0.05) and wear rate (0.3±0.02×10−4 mm3/Nm). Annealing resulted in alloys with good strength-ductility combinations due to appreciable γ' precipitation enhancement.

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