Damping characteristics of shape memory alloys on their inherent and intrinsic internal friction

Abstract

In this chapter, damping characteristics of the inherent and intrinsic internal friction (IFPT + IFI) peaks for Ti50Ni50, Ti50Ni50-xCux, Ti50Ni50-xFex, Ni2MnGa, Ni-Mn-Ti, and Cu-Al-Ni shape memory alloys (SMAs) are reviewed. Ti50Ni50 SMA exhibits obvious (IFPT + IFI) peaks with tan d above 0.02 during martensitic transformations, but they only exist in a narrow and low temperature range. Ti50Ni50-xCux (x ≥ 10) SMAs show higher (IFPT + IFI) peaks than Ti50Ni50 SMA because B19 martensite in Ti50Ni50-xCux SMAs is originated by substituting Ni with Cu atoms while R-phase in Ti50Ni50 SMA is caused by the introduction of abundant defects/dislocations. Ti50Ni48Fe2 and Ti50Ni47Fe3 SMAs also exhibit higher (IFPT + IFI) peaks than Ti50Ni50 SMA because R-phase formation is due to the substitution of Ni by Fe atoms rather than induced by introduced dislocations. However, the martensitic transformation temperatures of Ti50Ni50-xFex SMAs are suppressed to lower temperatures simultaneously by the addition of Fe atoms. Ni- Mn-Ti and Ni-Mn-Ga magnetic SMAs both exhibit relatively high martensitic transformation temperatures. Unfortunately, the undesirable brittle nature of Ni- Mn-Ti and Ni-Mn-Ga SMAs critically limits their workability and high-damping applications. Cu-Al-Ni SMAs exhibit acceptable martensitic transformation temperatures and good workability; however, their (IFPT + IFI) peaks are relatively low. Among these various types of SMAs, Ti50Ni40Cu10 SMA is more suitable for high-damping applications because it possesses the advantages of high (IFPT + IFI) peaks, adequate workability, and an acceptable martensitic transformation temperature near room temperature.