The influence of Ultrasonic Shot Peening (USP) was investigated on microstructure, hardness and corrosion behavior of a nitrogen stabilised stainless steel without nickel in simulated body fluid (SBF). Specimens of 11.5 mm diameter and 4.5 mm thickness were subjected to USP with 2 and 3 mm diameter shots of hard steel, for time periods of 30, 60, and 120 seconds, separately. The hardness and roughness of the surface were found to increase from the USP treatment. The microstructure of the specimens in the Un-USP and different USP treated conditions was examined using optical microscope, SEM and TEM. There was a drastic reduction in the size of initial grains of 36-micron size to fine grains of 15 nm in surface region from the USP treatment. There is progressive change in microstructure, from multidirectional slip to single direction and finally diaappear, from USP treated surface towards interior, up to certain depth, depending on the shot diameter and duration of USP. Corrosion resistance of the specimens in different USP treated conditions was studied in SBF and was found to increase from USP with shots of 3 mm diameter for 30 seconds and with shots of 2 mm diameter for 60 seconds. There was decrease in corrosion resistance from longer duration of USP treatment due to localised surface damage.

Magnesium-containing multi-principal element alloys (MPEAs) are promising for lightweight applications due to their low density, high specific strength, and biocompatibility. This study examines two Mg-Ti-Zn alloy compositions, equal molar MgTiZn (TZ) and Mg₄TiZn (4TZ), synthesized via ball milling followed by spark plasma sintering, focusing on their microstructures and corrosion behaviors. X-ray diffraction and transmission electron microscopy revealed the formation of intermetallic phases, including Ti₂Zn and Mg₂₁Zn₂₅ in TZ, while 4TZ exhibited a predominantly Mg-rich phase. Potentiodynamic polarization and immersion tests in 0.1 M NaCl solution showed that both alloys had good corrosion resistance, with values of 3.65 ± 0.65 µA/cm² for TZ and 4.58 ± 1.64 µA/cm² for 4TZ. This was attributed to the formation of a TiO₂-rich surface film in the TZ, as confirmed by X-ray photoelectron spectroscopy (XPS), which contributed to enhanced passivation and lower corrosion current density. Both alloys displayed high hardness, 5.5 ± 1.0 GPa for TZ and 5.1 ± 0.9 GPa for 4TZ, and high stiffness, with Young’s modulus values of 98.2 ± 11.2 GPa for TZ and 100.8 ± 9.6 GPa for 4TZ. These findings highlight the potential of incorporating Ti and Zn via mechanical alloying to improve the corrosion resistance of Mg-containing MPEAs and Mg-based alloys.