Damping Characteristics of Cu-Zn-Al Shape Memory Alloys

Abstract

A Cu-19.03Zn-13.14AI at % shape memory alloy has been investigated using: a) I.F. and Young's modulus measurements in the KHz range; b) tension-compression cycling at 0.5 Hz; c) calorimetric measurements. From a) and b) the damping characteristics of the alloy have been determined, whereas from c) the friction work during beta-martensite transformation has been calculated as 10 J/mol. .-IntroductionIt is well known that CuZnAl alloys show high damping features in the rnartensitic transition region and in the rnartensitic state at temperatures lower than Mf (1-4). The damping properties are frequency and strain-amplitude dependent (1,5), they are affected by the microstructure as well. It is generally accepted that in the martensitic state the elastic energy dissipation arises from the stress assisted motion of interfaces between variants, while the nature of the frictional forces acting on the interfaces are not yet known. At the martensitic transition an internal friction (I.F.) maximum usually occurs, which is associated to stressassisted motion of p-martensite interfaces, that is to martensite formation and reversion. The appearance of this maximum is sensitive to the thermal hystory of the material and to the cooling and heating rates. At the martensitic transition usually a decrease is observed in the Young's modulus, which is larger than expected from the anelasticity theory. On approaching the reversion temperature As from the low temperature side, a gradual non linear decrease is displayed by the Young's modulus; such a decrease starts far below As. The nature of such softening is not yet known. Several calorimetric studies have been performed to get a better understanding of the various phenomena linked to the martensitic transition, however only recently the complexity of such experiments has been realized. Thus the deduction of the free enthalpy associated with the transition requires a rather sophisticated analysis of the data, involving separation of the various contributions to the free energy, one of which has to do with energy dissipated as irreversible work associated to the frictional motion of the interfaces (6,7).ln order to to gain more insight on the nature of the energy dissipative motion of the interfaces, an investigation was undertaken, which combined I.F.measurements, mechanical cycling and calorimetric observations in one CuZnAl alloy. 2.-Experimental .-Alloy preparationThe atomic composition of the alloy used in the present experiments was 67.83 Cu, 19.03 Zn, and 13.14 Al. This composition was selected to minimize possible variations in DO3 order parameter in tho temperature range of our tests (233 -313 K). After melting, the Article published online by EDP Sciences and available at http://dx

Characterization and Evaluation of Shape Memory Effect of Cu-Zn-Al Shape Memory Alloy

“…In Cu-based and NiTi SMAs these damping properties have been observed partially. Especially Cu-Zn-Al shows superior damping property compared to other Cubased SMAs [18][19] based on whether they are in martensite phase or austenite phase [20]. Cu-Zn-Albased SMAs, on the other hand, are the subject of this study due to their low production cost and greater strain recovery when compared to other Cu-based SMAs [21].…”

Influence of porosity and hBN content on the damping capacity of metal matrix composites

“…There are well-known non-ferrous HDMs such as Mg [11,12], Mn-Cu [13,14], Cu-Zn-Al [15,16], and Ni-Ti [17,18]-based alloys, which have been somehow successfully applied on engineering solutions. Still, most of these materials remain rather expensive and with relatively low mechanical strength, consequently finding only a few limited applications [19].…”