Influence of Fine Particle Peening Treatment on Various Characteristics of Ti–Ni Shape Memory Alloys

Author:  Koichiro Nambu, Noboru Egami
Source:  ICSP-13
Doc ID:  2017113
Year of Publication:  2017
Abstract:  
Introduction: Ti–Ni shape-memory alloy (SMA) is an alloy exhibiting a shape-memory effect and a super-elastic effect because of the occurrence of martensitic and rhombohedral phases. SMAs are widely used in small actuators and drive elements of robots. In recent years, several studies have been conducted on the biocompatibility of SMAs and their use in medical devices. Accordingly, it is necessary to understand the change in the characteristics associated with the accumulation of fatigue damage in SMAs employed in high-cycle applications. So far, studies have been conducted on rotational bendingfatigue characteristics and compression-fatigue characteristics of SMAs [1–7]. However, when used for medical devices and the like, an allergy is induced because of the dissolution of Ni ions contained in SMAs. Hence, the surface is modified via particular treatments to improve the corrosion resistance and biocompatibility. In conventional studies, it has been reported that an amorphous structure is formed near the surface when treated with strong processing techniques such as the shot-peening treatment and fine-particle peening (FPP) treatment [8–10]. Furthermore,elution of Ni ions from the amorphous structure can be suppressed [11, 12]. However, studies on evaluating the fatigue property of SMAs using surface-modification treatments have not been conducted. In this study, the effects of the FPP treatment on the shape memory effect and fatigue strength characteristics of an SMA, which has been effective in improving the fatigue strength in steel materials [13–16], were investigated.