In this work grain growth associated with isochronous annealing in polycrystalline pure copper is studied using nonlinear ultrasonic method. In isochronous annealing, holding time is constant but annealing temperatures vary. It is observed that, grain growth due to isochronous annealing significantly influences the ultrasonic nonlinearity parameter, β. A decrease in nonlinearity parameter with increase in grain size is noticed. Further, micro-hardness measurements as well as metallographic results are presented to underscore the utility of the nonlinear ultrasonic method in gauging the progress of annealing. As the time and effort involved in this method is less, with suitable calibration, this method may be gainfully employed for determination of grain size on annealing. © 2015, Society for Experimental Mechanics.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Parag Ravindran

R. S. Mini

Annealing

Grain size and shape

Heat treatment

microstructure

Wave propagation

Annealing temperatures

Experimental investigations

ISOCHRONOUS ANNEALING

MICROHARDNESS MEASUREMENT

NON-LINEAR ULTRASONIC

NON-LINEARITY PARAMETER

Twin boundaries

ULTRASONIC NONLINEARITIES

Grain growth

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Experimental Mechanics

A multi-frequency nonlinear ultrasonic measurement is used to characterize grain size variations and distributions unambiguously. The ultrasonic nonlinearity parameter varies linearly with grain size in the Rayleigh scattering regime but deviates from linear behavior at the Rayleigh-to-stochastic transition zone. Frequency dependence of this parameter is found to be a reliable tool for rapid screening of materials where grain size varies widely. © 2019, The Minerals, Metals & Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

A Novel Multi-frequency Nonlinear Ultrasonic Approach for the Characterization of Annealed Polycrystalline Microstructure

Sensitivity of nonlinear ultrasonic method towards isothermal annealing in pure copper is investigated in this study. It was reported that, recovery, recrystallization and grain growth associated with annealing has profound influence on nonlinearity parameter. Presence of precipitates and secondary phase particles, and its effect on nonlinearity parameter was considered by many authors. However, in this study, focus is on the influence of grain-growth on nonlinearity parameter. Variation of non-linearity parameter, β, with different holding durations were analyzed. All the samples were annealed at a temperature above its recrystallization temperature. Further, metallography studies as well as hardness measurements were performed to understand the relationship between microstructural changes and ultrasonic nonlinearity parameter. © 2014 AIP Publishing LLC.

AIP Conference Proceedings

Characterization of annealing in polycrystalline copper using harmonic generation technique

Present study endeavors to establish the physical basis of an unprecedented trend in scatter, observed in nonlinear ultrasonic (NLU) parameter, associated with varying degree of crystallographic orientation change across crystallites in a polycrystalline material. It is shown that this scatter arises due to anisotropy in harmonics generation as a result of orientation change of slip systems in polycrystals with respect to the wave propagation direction. A near α titanium alloy has been taken as a model alloy to demonstrate this effect of crystallographic orientation change vis-à-vis change in the orientation of slip systems. Scale of crystal orientation change is shown to have a strong correlation with the degree of scatter in NLU measurements. Further, the study establishes the dominating effect of the scale of crystalline orientation change on harmonics generation as compared to variation in other microstructural parameters such as dislocation density, interface structure etc. Frequency distribution analysis of the scatter indicates that the distribution depends on the colony size which exhibits a linear correlation with standard deviation value. The dislocation string vibration model has been extended for harmonics generation in polycrystalline aggregates to explain the trend in the scatter during measurement of NLU parameter in the material. © 2012 American Institute of Physics.

Fulltext

Journal of Applied Physics

Scatter in nonlinear ultrasonic measurements due to crystallographic orientation change induced anisotropy in harmonics generation

This paper describes a new nonlinear ultrasonic (NLU) technique for creep damage characterization. Traditionally, nonlinear material response is evaluated at high amplitude levels. The present paper evaluates the nonlinear response of samples at much lower amplitude levels than used in any previous study of nonlinear material behavior. The newly observed nonlinear behavior occurs when dislocations are constrained between two quiescent lattice planes as defined by Cantrell. Three parameters are used to characterize the low amplitude nonlinear response during the progression of creep damage in 99.98% pure copper specimens studied here; these are parameters that characterize (a) the static displacement, (b) the second harmonic and (c) the third harmonic components of the ultrasonic through-transmitted signal. Various features of the received NLU amplitude vs. input amplitude to the ultrasonic transducer were observed to correlate well with micro-void concentrations caused by creep damage. © 2010 Elsevier Inc. All rights reserved.

Materials Characterization

Creep damage characterization using a low amplitude nonlinear ultrasonic technique

This paper describes the use of non-linear ultrasonic techniques for the characterization of material degradation in 99.98% pure copper due to high-temperature creep. Flat dog-bone-shaped specimens were subjected to constant load creep testing at different stress and temperature levels. Creep damage progression was monitored by conducting continuous and interrupted mode creep tests. In the case of continuous loading non-linear ultrasonic (NLU) measurements were conducted after fracture at different locations along the gage length of the sample. For interrupted tests the NLU measurements were conducted on different creep life fractions, through periodic interruption of the creep test. In all cases a through transmission NLU measurement technique was employed. Three different non-linear measurements, namely static displacement, second harmonic and third harmonic, were taken and their responses compared. The NLU measurements were found to be significantly sensitive to the extent of creep damage (∼200-2500% of base level), while the linear ultrasonic measurements, representing the change in longitudinal velocities, were only in the range 10-30% for a comparable creep damage level. NLU measurements carried out on fractured samples suggest that the NLU response was locally high at locations where the creep damage was concentrated, compared with other locations, even within the gage length of the specimen. This was confirmed using micrograph observations. Of the three non-linear measurements, the third harmonic data was most sensitive to creep damage. © 2009 Acta Materialia Inc.

Acta Materialia

Creep damage characterization using non-linear ultrasonic techniques

Systematic nonlinear ultrasonic (NLU) studies using longitudinal and guided surface acoustic waves (SAW) were conducted on AA7175-T735 aluminum alloy specimens that were plastically deformed to varying levels of residual strain. The variation of nonlinear ultrasonic (NLU) parameter (A2 / A12) as a function of residual plastic deformation, suggests an increase in NLU parameter at a slow rate up to a certain level of deformation and thereafter there is a significant increase in NLU parameter with further increase in the strain level. X-ray diffraction methods to characterize line broadening and etch pit dislocation distribution studies suggest that the smaller rate of increase in NLU parameter could be due to the increase in the dislocation density and higher rate of increase could be caused by formation of cellular dislocation pattern. Thus, our study shows that it is possible to study the two stage dislocation dynamics observed during residual plastic deformation of Al alloy 7175-T7351 using nonlinear ultrasonic technique. © 2009 Elsevier B.V. All rights reserved.

Materials Science and Engineering A

Observation of two stage dislocation dynamics from nonlinear ultrasonic response during the plastic deformation of AA7175-T7351 aluminum alloy

An Experimental Investigation on the Influence of Annealed Microstructure on Wave Propagation

Journal	Data powered by TypesetExperimental Mechanics
Publisher	Data powered by TypesetSpringer New York LLC
ISSN	00144851
Open Access	No