Enhancing Properties of TiZrHfNbTa Alloy by Surface Layers Nanostructuring Using Cryogenic Ultrasonic Impact Treatment

A multicomponent Ti28 Zr29 Hf28 Nb5 Ta10 alloy was subjected to ultrasonic impact treatment (UIT) carried out in the air (at room temperature) and in liquid nitrogen (at cryogenic temperature). X-ray diffraction (XRD) analysis shows that the UIT-induced severe plastic deformation did not change the single-bcc structure but results in a significant increase of dislocation density, grain refinement (the XRD-assessed grain size decreases down to ~25 nm after cryo-UIT), and formation of compressive residual stresses. Indentation tests show that the surface nanostructuring leads to the ~30% increase in the instrumental hardness of the cryo-UIT processed specimen (HIT ~5.4 GPa) and to a slight increase in elastic modulus (E ~90.5 GPa). The UIT processes also led to an increase in the corrosion potential and a decrease in the corrosion current density indicating the enhanced corrosion resistance in 0.9 NaCl physiological solution. The nanostructured surface was shown to experience uniform dissolution and quicker formation of the protective oxide layer.