Change of Acoustic Emission Characteristics during Temperature Induced Transition from Twinning to Dislocation Slip under Compression in Polycrystalline Sn

Abstract

In this study, acoustic emission (AE) measurements on polycrystalline tin as a function of temperature at different driving rates under compression were carried out. It is shown that there is a definite difference between the acoustic emission characteristics belonging to twinning (low temperatures) as well as to dislocation slip (high temperatures). The stress averaged values of the exponents of the energy probability density functions decreased from = 1.45 ± 0.05 (−60 °C) to = 1.20 ± 0.15 (50 °C) at a driving rate of , and the total acoustic energy decreased by three orders of magnitude with increasing temperature. In addition, the exponent γ in the scaling relation SAE~DAEγ (SAE is the area and DAEis the duration) also shows similar temperature dependence (changing from γ = 1.78 ± 0.08 to γ = 1.35 ± 0.05), illustrating that the avalanche statistics belong to two different microscopic deformation mechanisms. The power law scaling relations were also analyzed, taking into account that the detected signal is always the convolution of the source signal and the transfer function of the system. It was obtained that approximate values of the power exponents can be obtained from the parts of the above functions, belonging to large values of parameters. At short duration times, the attenuation effect of the AE detection system dominates the time dependence, from which the characteristic attenuation time, τa, was determined as τa≅ 70 μs.

Denouement of the Energy-Amplitude and Size-Amplitude Enigma for Acoustic-Emission Investigations of Materials

“…For alloy B, the curved first part reflects the transfer effects. It is possible to estimate the acoustic-wave-attenuation time (see, e.g., Equation (6) and Figure 8 in [28]) from this part, and ≅ 20 μS was obtained. Thus, points below about 200 μS can be left out from the fit, since for these > 0.01.…”

“…the scaling prefactor, s i , depends explicitly on the duration of the avalanche, and this can be different for different mechanisms/different avalanche profiles (the index i serves to distinguish between groups of signals belonging to different avalanche profiles). It was also emphasized in [28] that, in general, the universality of avalanches contradicts expectations for identifying different underlying physical processes, so it is difficult to specify experimentally measurable parameters that are characteristic for different avalanche profiles. In fact, our formalism would provide a solution for this problem in the following way.…”

Clustering Characterization of Acoustic Emission Signals Belonging to Twinning and Dislocation Slip during Plastic Deformation of Polycrystalline Sn

“…The dominant deformation mechanism in a given material depends on various parameters, such as the rate of the deformation [ 23 ] and the temperature [ 24 , 25 , 26 ], or on the crystallographic direction of the deformation [ 27 ]. For tin, at low temperatures, the deformation takes place with twinning at low deformation rates, which turns into the collective motion of dislocations at higher temperatures [ 26 ]. Due to the intermittent character of the deformation process, we can detect acoustic emission signals.…”

“…Due to the intermittent character of the deformation process, we can detect acoustic emission signals. It was shown [ 26 ], that by changing the temperature, and consequently, changing the deformation mechanism, the characteristics of the detected acoustic emission signal also change. With increasing temperature, the number of avalanches, as well as a set of exponents of different avalanche parameters (energy, size) decreased significantly.…”

“…In this study, in order to study the AE signals in more detail, in accordance with the results of [ 26 ], we carry out acoustic emission measurement during the deformation of polycrystalline tin samples at two characteristic temperatures belonging to twinning as well as dislocation slip. The recorded signals will be processed with the means of the ASK method to explore their differences in the spectral properties, and to see what other noise sources are active besides the dominant deformation mechanisms.…”