Thermal Memory Degradation in a Cu-Zn-Al Shape Memory Alloy During Thermal Cycling with Free Air Cooling

Abstract

A fragment of a Cu-15Zn-6Al (mass%) shape memory alloy (SMA), in hot rolled-water quenched condition, was subjected to thermal cycling performed by means of a differential scanning calorimetry (DSC) device. Each cycle comprised controlled heating, isothermal maintaining, and free air-cooling, repeated three times, up to maximum temperatures increased by every 10 K, between 450 and 490 K, aiming to reproduce actual functioning conditions of a SM electrical actuator with uncontrolled cooling. Both the endothermic peaks, associated with thermally induced reversion of martensite to austenite, and their derivatives were analyzed in terms of critical transformation temperatures and specific enthalpy absorptions and in terms of transformation rates, respectively, with the aim of revealing their variational tendencies with increasing heating temperature to the maximum. The progressive decay of reverse martensitic transformation was associated with the reciprocal blocking of differentially oriented populations of stabilized lath-martensite needles, observed by scanning electron microscopy.

Thermal Stabilization of NiTiCuV Shape Memory Alloys: Observations During Elastocaloric Training

“…However, an increased interest in the elastocaloric effect is noticeable as well [18][19][20][21][22].…”

Comparative topographic study of surface micro‐relief of primary martensite plates in shape memory alloys with different crystalline structures

“…From previous studies performed on quenched specimens of these alloys, with average grain size of 100 -150610 -6 m, the critical temperature for the start of martensite reversion to parent phase during heating was determined by dynamic mechanical Faculty of Materials Science & Engineering, The "Gheorghe Asachi", Technikal University of lasi, Bd.D. Mangeron 61A, 700050 Iasi, Romania analyzer as A s = 522 K, for Fe-base SMA and by differential scanning calorimetry as A s = 393 K, for Cu-base SMA [12,13]. Since the critical temperature for the start of martensite formation during cooling (M s ) was higher than room temperature (RT) at Fe-Mn-Si-Cr-Ni SMAs with similar chemical composition [14] and it was determined as M s = 381 K at the Cu-15 Zn-6 Al SMA [13], it follows that both alloys under study are martensitic at RT [13,14].…”

Comparative Studies of Work-developing Capacity of Shape Memory Alloys (SMA) and Polymers

“…The former used specimens lighter than 50 mg, cut with a BUEHLER low speed saw and analysed by means of a 2920 Modulated DSC TA INSTRUMENTS unit, with measuring accuracies of ± 0.1 K for temperature and ± 1 W/kg for heat flow, equipped with professional software. The specimens were heated and cooled with 10 K/min, under He + Ar protective atmosphere [14].…”