Application of ultrasonic nanocrystal surface modification (UNSM) technique for surface strengthening of titanium and titanium alloys: a mini review

Abstract Titanium and titanium alloys have been restricted in tribology-related field, because of their disadvantages, such as low surface hardness, high friction coefficient and poor wear resistance. Various surface modification techniques have been applied to improve their deficiencies. As a new technology of severe surface plastic deformation, ultrasonic nanocrystal surface modification (UNSM) technique has been widely used to realize the surface treatment of various materials, and also has attracted wide attention in many engineering fields. This review begins with a brief introductionof the basic concept and the modification mechanism of the UNSM technique. The specific applications of the UNSM technique for improving the tribological and fatigue properties of titanium and its alloys were reviewed and summarized.