Motion of dislocations and interfaces during deformation of martensitic Cu–Al–Ni crystals

doi:10.1016/S1359-6454(99)00374-2

Acta Materialia

Volume 48, Issue 5, 14 March 2000, Pages 1141-1151

https://doi.org/10.1016/S1359-6454(99)00374-2 Get rights and content

Abstract

Investigations of the ultrasonic strain amplitude-dependent internal friction (ADIF) and of the influence of ultrasonic vibrations on the macroplastic strain (the acoustoplastic effect) have been performed in situ during deformation of quenched Cu–Al–Ni single crystals in the β′₁ martensitic phase. The effect of the macroscopic plastic strain rate on the ADIF and acoustoplastic effect as well as the kinetics of the acoustoplastic effect has been studied. The results of in situ ADIF measurements are compared with data on the ADIF temperature dependence. Observed regularities are attributed to differences in the mechanisms of the macroplastic deformation of the martensitic phase, related to the motion of intervariant interfaces, and of the reversible anelastic strain, which, at ultrasonic frequencies and moderate strain amplitudes, is largely due to the oscillatory motion of the partial dislocations. The conclusion has been drawn that the dynamics of partial dislocations at temperatures of 210–300 K is to a great extent determined by their interaction with atmospheres of mobile pinners with saturated density. Simultaneous measurements of the ADIF and acoustoplastic effect allows the conclusion that, for high oscillatory strain amplitudes, the breakthrough of partial dislocations beyond the mobile atmospheres of pinners initiates the step-like accumulation of the macroplastic strain due to the motion of intervariant boundaries.

Introduction

It is well known that the β′₁ martensitic phase undergoes macroscopic plastic deformation under quasistatic stress by growth of favourably oriented martensitic variants through displacement of intervariant boundaries [1]. The internal friction (IF) during thermoelastic martensitic transformation and in the martensitic phase has also been traditionally attributed to the oscillatory motion of interphase/intervariant boundaries, see for example the review in Ref. [2]. On the other hand, dislocation mechanisms of the strain amplitude dependence of the IF in the β′₁ martensite were also suggested for the range of moderate strain amplitudes 3, 4, 5, 6, 7, 8. The acoustic waves giving rise to the dislocation strain amplitude-dependent internal friction (ADIF) are known to influence the process of macroscopic plastic deformation causing the so-called acoustoplastic effect (APE). The APE appears as an acceleration of creep [9] or as a decrease in flow stress during active deformation [10] when an oscillatory component is superimposed on a static mechanical load. The APE originates from the additional irreversible plastic strain in contrast to the strain amplitude-dependent anelasticity, which is due to the reversible anelastic strain. Therefore, simultaneous measurements of the ADIF and the APE may allow one to control (via the oscillatory strain amplitude) and register separately both the reversible anelastic and irreversible plastic strain (related to the ADIF and the APE, respectively). In view of the different mechanisms, suggested for the macroplastic and reversible microplastic deformation of the β′₁ martensite, simultaneous investigations of the APE and the ADIF are of considerable interest. An important point during in situ measurements of the IF is the distinction between transient and structural IF. The transient IF component is coupled with the macroscopic plastic strain rate and, as a consequence, with the irreversible motion of interfaces. If the IF is measured at sufficiently high ultrasonic frequencies, it reflects only the oscillatory motion of defects so that the transient IF component, which is inversely proportional to the frequency of oscillations, can be neglected.

Thus, measurements of the ADIF and APE at ultrasonic frequencies are an essential condition for observation separately of reversible anelastic and irreversible macroplastic strain.

The APE is widely investigated for dislocation mechanisms of plastic deformation, but it is virtually not studied in relation to different deformation modes in alloys undergoing a thermoelastic martensitic transformation. Recently, the acousto-pseudoelastic effect was found [11], i.e. the effect of ultrasonic oscillations on the pseudoelastic deformation caused by the reversible thermoelastic transformation under stress (so-called transformation pseudoelasticity [1]). In the present work the ADIF and the APE have been investigated for a frequency of vibrations of about 100 kHz during quasistatic deformation of quenched Cu–Al–Ni crystals in the β′₁ martensitic phase. The Cu–Al–Ni system is the most appropriate for such an investigation since the ordinary dislocation plasticity is strongly suppressed in these crystals in contrast to, for example, NiTi alloys.

Section snippets

Experimental details

Single crystals of Cu–13.2 wt% Al–4.0 wt% Ni were purchased from Orimi Steel, St. Petersburg, Russia. The transformation temperatures $M_{s} =371 K$ , $M_{f} =350 K$ , $A_{s} =363 K$ , $A_{f} =379 K$ were determined by DSC. Samples of about $1×2.5 mm^{2}$ cross-section and three half-wavelengths of ultrasound (46.7 mm) in length were spark cut from rods with [100] β-phase orientation. They were quenched into water after betatizing at 1173 K for 900 s. The samples had polyvariant β′₁ martensitic structure.

A computer-controlled set-up

Results

Figure 1 shows the load–sag curve registered during three-point bending of a sample. The maximum stress in the surface layer is derived from the applied load, assuming elastic bending of the sample. Points A–G correspond to the measurements of the strain amplitude dependence of the IF and APE. The cross-head movement rate during measurements of the strain amplitude dependence was set to 10⁻⁵ (points A–E), 3×10⁻⁵ (point F) and 10⁻⁴ mm/s (point G). The drops of the deforming load in points A–G are

Interaction of moving dislocations with atmospheres of mobile pinning points

According to Refs 6, 7, 8, the structural ADIF and reversible anelastic strain of the β′₁ martensitic phase of Cu–Al–Ni single crystals at moderate strain amplitudes (ε₀<2×10⁻⁴) and ultrasonic frequencies are due to the hysteretic motion of an ordered network of partial dislocations inside the martensitic variants. The two-stage increase of the ADIF with the rise of ε₀, observed at room temperature for quenched Cu–Al–Ni crystals 5, 6, was explained by the transition from the dislocation motion

Conclusions

An effect of ultrasonic oscillations (frequency of about 100 kHz) on the martensitic plasticity of the polyvariant crystals has been put in evidence: the superposition of the ultrasonic oscillations on a quasistatic stress gives rise to an additional plastic strain.

The present results strongly support the concept of atmospheres of mobile point defects, controlling the mobility of partial dislocations in the quenched β′₁ Cu–Al–Ni martensite. Simultaneous measurements of the strain

Acknowledgements

The partial support of the work through INTAS project No. 96-2142 is gratefully acknowledged. The authors appreciate the fruitful discussions with Dr R. Gotthardt.

References (21)

S. Kustov et al.
Acta mater.
(1998)
K.V. Sapozhnikov et al.
Scripta mater.
(1996)
R. Pohlman et al.
Ultrasonics
(1966)
J. Stoiber et al.
Mater. Sci. Engng
(1993)
J.W. Christian
Metall. Trans.
(1982)
J. Van Humbeeck et al.
Z. Metallk.
(1995)
W. Dejonghe et al.
Metals Sci.
(1977)
S. Koshimizu et al.
J. Physique
(1982)
S.B. Kustov et al.
J. Physique IV, Suppl. J. Physique III
(1995)
S.B. Kustov et al.

There are more references available in the full text version of this article.

Cited by (41)

Power ultrasonics for additive and hybrid manufacturing
2023, Power Ultrasonics: Applications of High-Intensity Ultrasound, Second Edition
This chapter explores the ultrasonic additive manufacturing (UAM) process. This process is an advanced, solid-state, metal additive/subtractive hybrid manufacturing process. The process combines high-power ultrasonic welding and computer numerical control milling to fabricate solid metal components, layer by layer, from metal foils. The chapter discusses the process fundamentals and three key abilities of UAM: complicated geometries, dissimilar material bonding, and object embedment. Combining these three key abilities positions UAM as a unique and attractive method to create metal matrix–based freeform multifunctional structures for high-value engineering applications.
Internal friction in complex ferroelastic twin patterns
2022, Acta Materialia
Citation Excerpt :
Similarly, point defects, hydrogen and precipitates in TiNi alloys exhibit different effects on the IF due to their different pinning ability, whereby precipitates hinder twin interfaces motion [11,12]. Anelastic twin boundary dynamics in ferroelastic LaAlO3 in the depinned state [22] follows power-law statistics and similar effects were observed in shape memory alloys Ni-Fe-Ga-Co and Cu-Al-Ni [23–25]. Such power law dependencies are a fingerprint of avalanche movements which are observed by acoustic emission or heat flow experiments in ferroelastic materials and martensites [26–32].
We report the first attempt to study the internal friction (IF) of complex ferroelastic twin patterns by atomistic molecular dynamics simulations. At different stress amplitudes, linear and non-linear IF regimes are observed. They are separated by a pinning/depinning threshold. At external stresses below the pinning/depinning threshold, a low linear IF background is nearly independent of temperature and configuration of the twin patterns. With increasing stresses, twin boundary motions generate non-linear anelasticity where the stress dependent IF increases to a maximum and then decays. The IF is directly related to the motion of needle twins. The effects of vacancy pinning and thermal activation are studied. The IF maximum is reduced and shifted to higher stresses by extrinsic pinning effects. The IF maximum decreases further with increasing temperature from 8 × 10⁻⁶ T_c to 8 × 10⁻⁴ T_c where T_c is the ferroelastic transition temperature. The non-linear IF depends by power law on the strain with exponents near 2 below the IF maximum and -1 at strains higher than the maximum. Vacancies destroy the power law and break the scale invariance of the domain boundary movements. The overall picture obtained in this study is consistent with basic experimental observations.
Reply to comment on: “On the effect of room temperature ageing of Ni-rich Ni[sbnd]Ti alloys”
2016, Scripta Materialia
Previous observations of unusual strong room temperature (RT) ageing effect in Ni-rich NiTi alloys are confirmed. We draw attention to our interpretations of the uncovered effect suggested in our previous work, which imply the involvement of defect-assisted rather than long-range bulk diffusion. New experimental results are presented which allow us to select sweeping-up of quenched-in defects by interfaces moving during martensitic transformation as the key ingredient of strong RT ageing. We link the uncovered effect with other manifestations of low-temperature (down to 15–20 K) diffusion of quenched-in defects in both twinned and faulted martensites, assisted by linear/planar structural elements of martensitic structures.
Strong heating rate-dependent deterioration of shape memory effect in up/step quenched Cu-based alloys: A ductile Cu-Al-Mn alloy as an example
2016, Acta Materialia
Citation Excerpt :
Shape memory alloys (SMAs) have commercial potential for practical applications due to their unique shape memory effect (SME) and super-elasticity [1]. Among them, Cu-based SMAs, such as Cu-Zn-Al [2–4] and CuAlNi alloys [5–8], are of special interest due to their low cost as compared to the expensive TiNi-based SMAs. However, because of the highly ordered parent phase, Cu-based SMAs are too brittle to be cold processed [9].
It is generally believed that an up/step-quenching treatment can suppress the deterioration of shape memory effect (SME) due to the martensitic stabilization. However, recent studies have indicated that the SME in an up-quenched ductile CuAlMn alloy dropped drastically as lowering the recovery heating rate. To understand whether the above strong heating rate-dependent deterioration in the SME can be ascribed to the martensitic stabilization, we carefully investigated the microstructural differences in an up-quenched Cu-17.0Al-10.5Mn (at.%) alloy after deformation and then heating at different rates. The effect of up-quenching time on the SME deterioration induced by lower heating rates was also studied. The results showed that the martensitic stabilization is responsible for strong heating rate-dependent deterioration in the SME in the up-quenched CuAlMn alloy, and whether a certain up-quenching treatment can suppress its occurrence is strongly dependent on the recovery heating rate. Available data clearly showed that this dependence also exists in other up/step-quenched Cu-based alloys. The migration, cluster and even collapse of thermodynamically non-equilibrium quenched-in vacancies at the martensite interfaces result in this dependence. The martensite interfaces pinned by the collapsed vacancies cannot be de-pinned through thermal activation.
Power ultrasonics for additive manufacturing and consolidating of materials
2015, Power Ultrasonics: Applications of High-Intensity Ultrasound
This chapter explores the ultrasonic additive manufacturing (UAM) advanced solid-state metal additive/subtractive manufacturing process that combines ultrasonic welding and computer numerical control milling to fabricate solid metal components, layer-by-layer, from metal foils. The chapter will discuss the three key abilities of UAM: complicated geometries, dissimilar material bonding, and object embedment. The combination of these three key abilities places UAM as a most attractive method with which to create metal matrix-based freeform smart structures for high-value engineering applications.
Inherent internal friction of Ti<inf>50</inf>Ni<inf>50-</inf><inf>x</inf>Cu<inf>x</inf> shape memory alloys measured under isothermal conditions
2014, Journal of Alloys and Compounds
Ti₅₀Ni₅₀₋_xCu_x (x ⩾ 10) SMAs with (IF_PT + IF_I)_B2→B19 and/or (IF_PT + IF_I)_B19→B19′ peaks exhibited higher damping capacities than the Ti₅₀Ni₄₅Cu₅ SMA did with only a (IF_PT + IF_I)_B2→B19′ peak, because the twinning shear values of the {0 1 1} compound twin and {1 1 1} Type I twin in B19 martensite are much lower than that of the 〈0 1 1〉 Type II twin in B19′ martensite. Compared with other Ti₅₀Ni₄₀₋_xCu_x SMAs with higher Cu contents, the Ti₅₀Ni₄₀Cu₁₀ SMA was more suitable for high-damping applications because it had the advantages of both an acceptable inherent internal friction and adequate workability. The Ti₅₀Ni₄₀Cu₁₀ SMA showed the highest inherent internal friction of tan δ > 0.03 at room temperature, and is thus a potential high-damping material for use at a steady temperature.

View all citing articles on Scopus

View full text

Motion of dislocations and interfaces during deformation of martensitic Cu–Al–Ni crystals

Abstract

Introduction

Section snippets

Experimental details

Results

Interaction of moving dislocations with atmospheres of mobile pinning points

Conclusions

Acknowledgements

Acta mater.

Scripta mater.

Ultrasonics

Mater. Sci. Engng

Metall. Trans.

Z. Metallk.

Metals Sci.

J. Physique

J. Physique IV, Suppl. J. Physique III