Initial stages of γ2 precipitation in an aged Cu-Al-Ni shape memory alloy

Zárubová, N.; Gemperle, A.; Novák, V.

doi:10.1016/s0921-5093(96)10520-7

Cited by 48 publications

(25 citation statements)

References 26 publications

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“…The transition curves of the forward and reverse transitions for the Cu-Al-Ni-xTi (x = 0.4, 0.7 and 1.0 mass%) aged at different times and temperatures are illustrated in It was found that with an increase in aging time and temperature, the transition temperatures shift toward high temperatures, which is in agreement with other researchers [20][21][22][23][24]. This shifting is mainly attributed to the type and morphology of the martensitic phase, as well as the presence of the precipitates [25,26].…”

Section: Dsc Analysissupporting

confidence: 88%

X-phase precipitation in aging of Cu–Al–Ni–xTi shape memory alloys and its influence on phase transition behavior

Saud

Hamzah

Abubakar

et al. 2015

J Therm Anal Calorim

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The present work aims to investigate the aging treatment effects on the microstructure, transition characteristics, and mechanical properties of Cu-Al-Ni-xTi shape memory alloys. The aging treatment of the homogenized and modified alloys of Cu-Al-Ni-xTi results in variations of the martensite morphology, volume fraction, and precipitate size. These variations in the features of precipitates have an obvious effect on transition behavior and mechanical properties. The transition temperatures are increased slightly with an increase in the aging time and temperatures; such increase is mainly attributed to changes in the c 0 1 and b 0 1 morphology and distribution, along with the precipitates. The thermodynamic parameters (DH and DS) tend to decrease with an increase in the aging time and temperatures. Moreover, the brittleness, low strength, and poor processability of Cu-Al-Ni alloys greatly limit their application. We attempted to improve the mechanical properties without losing the thermoelastic properties through the additions of Ti and appropriate aging treatments. The highest tensile strength and strain of 640 MPa and 4.3 % were obtained in alloy of Cu-Al-Ni-0.7 mass% Ti aged at 250°C for 24 h and 100°C for 48 h, respectively. The shape memory behavior of the alloys was studied using a specially designed machine. The strain recovery by shape memory effect of the alloys increases with an increase in the aging tomes and temperature, where the highest recovery (100 %) is obtained with the alloy of Cu-Al-Ni-0.7 mass% Ti after being aged at 250°C for 24 h.

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Section: Dsc Analysissupporting

confidence: 88%

X-phase precipitation in aging of Cu–Al–Ni–xTi shape memory alloys and its influence on phase transition behavior

Saud

Hamzah

Abubakar

et al. 2015

J Therm Anal Calorim

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“…Many discussions have already been focused on the origin of the transformation temperature increase [2][3][4][5][6] and the present results clearly show that the main modifications are not induced by the 72 precipitation. On the other hand, the sharp rise of As and Ms, similarly observed in the two samples, could be ascribed to the recovery of the second neighbouring order in the austenite phase [6][7].…”

Section: Discussionsupporting

confidence: 64%

“…As shown in figure 1, after an annealing of only 20 minutes, small precipitates have formed in some domains of the austenite. The cuboi'dal shape of these precipitates is characteristic of the gamma 2 phase (Q19AI4); usually they are observed in CuAINi alloys only for annealing above 200 °C [3][4][5]. In addition, the diffraction pattern taken ESOMAT 2000 from an array of precipitates shows that the diffraction spots of the precipitates are located at nxg/3 in one <110> direction of the bcc matrix (figure 1).…”

Section: Polycrystalmentioning

confidence: 99%

“…Ageing phenomena observed in CuAINi austenite are commonly described in three more or less independent stages associated with reordering process and precipitation of stable phases [2]. In the first one, typically for an annealing below 200 °C, some authors have observed short range ordering, but the transformation temperatures are not significantly changed [3][4]. The second stage is also associated with ordering phenomena but the gamma 2 (J2 -Cu 9 Al 4 ) or other rich aluminium phase precipitation could also occur and the transformation temperatures are increased.…”

Section: Introductionmentioning

confidence: 99%

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TEM study of the austenitic phase of high Ms CuAlNi alloys

et al. 2001

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Abstract. CuAINi shape memory alloys, with Ms close to 130 °C (in the as-quenched state) have been studied on single crystalline and polycrystalline samples. The specimens have been quenched after heat treatment at 850 °C. The structural study discussed in the present paper has been performed using electrical resistivity and TEM (Transmission Electron Microscopy) analysis. The electron diffraction patterns show that the austenite of the two as-quenched samples is a disordered and body-centred cubic structure. Then, after one annealing at 165 °C performed in the TEM, the polycrystalline austenite reorders in a facecentred cubic structure (L2 r type), while the single crystalline austenite (annealed at 172 °C) stays in the disordered state. Nevertheless, during the heating of the single crystal sample above Ap, ordered precipitates appear in the parent phase along the former martensite-martensite interface traces. In addition, precipitates of the Cu 9 AL, (y 2 ) phase are evidenced in the two samples after annealings below 172 °C. These observations, the structural difference between the single-and the polycrystalline austenite and the low temperature precipitation of the Y2 phase, are quite original and have to be discussed by taking into consideration previous investigations performed on similar alloys.

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“…Produljenje opada nakon što su tvrdoća i čvrstoća dosegnule maksimalnu vrijednost. 55 Zarubova et al 56 ispitivali su utjecaj starenja na martenzitnu transformaciju slitine CuAlNi s w(Cu) = 14,3 % i w(Ni) = 4,1 %. Promjena temperatura faznih transformacija slitine u ovisnosti o temperaturi starenja prikazana je na slici 8.…”

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Slitine s prisjetljivosti oblika (II. dio): podjela, proizvodnja i primjena

2014

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Slitine s prisjetljivosti oblika (II. dio): podjela, proizvodnja i primjena Slitine s prisjetljivosti oblika funkcionalni su "pametni" materijali s jedinstvenim svojstvom prisjetljivosti oblika. Prisjetljivost oblika karakteristična je sposobnost materijala koja je posljedica martenzitne fazne transformacije, a karakterizira je vraćanje slitine u oblik koji je imala prije deformacije. U radu su detaljno objašnjene slitine s prisjetljivosti oblika s gledišta njihove podjele, proizvodnje i primjene. U industrijskoj primjeni najčešće se upotrebljavaju slitine na bazi nikla i titanija, te slitine na bazi bakra. Slitine na bazi željeza i plemenitih metala još uvijek nemaju značajniju industrijsku primjenu. Slitine s prisjetljivosti oblika uglavnom se proizvode postupcima indukcijskog taljenja, brzog očvršćivanja (primjerice melt spinning) i kontinuiranog lijevanja.

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Initial stages of γ2 precipitation in an aged Cu-Al-Ni shape memory alloy

Cited by 48 publications

References 26 publications

X-phase precipitation in aging of Cu–Al–Ni–xTi shape memory alloys and its influence on phase transition behavior

X-phase precipitation in aging of Cu–Al–Ni–xTi shape memory alloys and its influence on phase transition behavior

TEM study of the austenitic phase of high Ms CuAlNi alloys

Slitine s prisjetljivosti oblika (II. dio): podjela, proizvodnja i primjena

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