Amplitude Dependent Internal Friction of CuAlMn Shape Memory Alloys

Abstract

The strain amplitude dependent internal friction at room temperature and the transition temperatures of CuAlMn-shape memory alloys with Al contents from 8.9 wt.% to 12.7 wt.% and Mn contents from 4.7 wt.% to 9.3 wt.% were investigated. The investigated strain range was 10-6 - 10-3. Rods of various compositions were die cast and machined to single clamped damping bars. Their transition temperatures and amplitude dependent damping was determined in as cast and homogenized state. The damping in the investigated shape memory alloys was found to be generally much higher than in metals without martensitic transition. In as cast state some alloys exceeded the damping of a Sonoston type alloy measured in comparison for strains higher than 3 x 10-5. The influence of grain size on damping was investigated by additional sand casting and the use of Boron for grain refinement. It was found that only the material with the biggest grains had a noticeable higher damping over the whole measured strain range. Homogenization heat treatment can still extremely increase the damping of CuAlMn alloys. After homogenization this extremely high damping decreases slowly to medium values in the order of as cast alloys.

A Numerical Method to Model Non-linear Damping Behaviour of Martensitic Shape Memory Alloys

“…Metals alloys, as well as severe high damping alloys, show elliptical hysteresis cycles with linear damping, including viscous damping, hysteretic damping, and linear rate depending damping, while the hysteresis cycles show a more sophisticated shape with a nonlinear damping (Figure 1) [16]. In case of SMA materials, frequency and amplitude dependencies of damping dependencies have been reported in many studies [12,17]. The intrinsic amplitude-dependent damping is associated to two different phenomena: pseudo-elasticity and the dissipation of energy in the martensitic state (Figure 2).…”

Impact of Alloy Composition and Thermal Stabilization on Martensitic Phase Transformation Structures in CuAlMn Shape Memory Alloys

“…Higher ratio of e/a results in high amounts of various cast related defects like heat cracks or cavities as seen at Figure 1. The samples were prepared by induction melting Ductility can be preserved by an increase of the quenching medium temperature above the phase transformation temperature 6 . The material will be kept at boiling temperature for 3 minutes.…”

“…The austenitic β-phase arranged to the lower order system β 1 (L21; Cu2AlMn) and martensitic phase stabilization of (unstable) β´3 (18R) to (stable) γ´3 (2H) ratio can be adjusted by quenching and the amount of aluminium (Al) and manganese (Mn) 3,4,5 . In 6,7 heat treatments above 1073 K and quenching are considered to improve the damping capacity. Small quenching rates and also low temperature ageing pins (by point defects) the system by increasing the amount of γ´3 which leads to reduced SME, damping capacity and increased martensite start (M S ) temperatures 8 .…”

Dynamic characteristics of Mn-Cu high damping alloy subjected to impact load

“…The Mn-Cu high damping alloy is a typical twin-type damping alloy and its main elements are Mn, Cu, Al, Fe, and Ni. Commercially available Mn-Cu based damping alloys include Sonoston, 1 Incramute, 2 ABPOPA, 3 and M2052 (Mn-20Cu-5Ni-2Fe). 4 Among them, the M2052 alloy is characterized by high damping characteristics, high strength (comparable to structural steel), high ductility, and fine processing performance, and therefore, offers the best performance.…”