Electrical and mechanical characterization of two-phase alloys by means of scanning probe microscopy in dynamic impedance spectroscopy mode Anna Arutunow ⇑ , Mateusz Tomasz Tobiszewski, Kazimierz Darowicki Department of Electrochemistry, Corrosion and Materials Engineering, Gdan ´sk University of Technology, Narutowicza 11/12, 80-233 Gdan ´sk, Poland article info Article history: Received 26 June 2014 Received in revised form 4 August 2014 Accepted 26 August 2014 Available online 16 September 2014 Keywords: Nanocontact Impedance Nanoimpedance AFM SPM DIS abstract Dynamic impedance spectroscopy, evaluated for measuring non-stationary systems, was used in combi- nation with scanning probe microscope. Using this approach, localized impedance measurements in the AFM contact mode could be carried out. Additionally, impedance–force curves were made at each phase of investigated materials to illustrate the relation between impedance and the force applied to a probe. Therefore, correlation of electrical and mechanical properties with particular phases of investigated two- phase alloys was made possible. The materials used in this study were spheroidal graphite cast iron and 2205 duplex stainless steel, both materials with clearly defined phases having significantly different properties. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction A.C. impedance techniques are commonly used in many research areas. Generally they are employed to characterize mac- roscopic surfaces or bulk properties of different materials. Thus, obtained results are averaged over the area or volume of an exam- ined sample. In order to register localized impedance spectra on different grains, phases and inclusions on the surface, important developments have been made. Two main approaches are avail- able: a micro-cell technique [1–5] and scanning probe microscopy (SPM) [6–9]. The micro-cell technique is well-established and used for in-situ examinations of metals in electrolyte. On the other hand, impedance measurements performed by means of scanning probe microscopy are mainly ex-situ evaluations. Therefore, impedance measured with micro-cell is of electrochemical kind, whereas SPM-based impedance is of electrical type. The time required to register the full impedance spectrum is relatively long, since in both techniques impedance spectra are made point by point [10–15]. If the localized impedance measure- ments are required, single frequency is utilized in order to mini- mize the time of scanning [9,16,7]. The probe moves across the surface while the time at each point needs to be relatively short. Unfortunately, the single frequency measurement is less informa- tive than the one, where full impedance spectrum is obtained. To make a compromise between full spectra and single frequency measurements, dynamic impedance spectroscopy (DIS) technique was proposed and applied to atomic force microscopy [17]. In DIS technique, the voltage perturbation signal consists of several frequencies, which are generated simultaneously. The response signal is registered and decomposed to individual components with Short Time Fourier Transformation (STFT). Details of dynamic impedance spectroscopy methodology, which originally applied to electrochemical phenomena, are described in a series of publica- tions [18–21]. Due to the advantage of performing analysis under non-stationary conditions, DIS has already prove its worth in a variety of electrochemical and corrosion studies [22–26]. Evolution of the scanning probe microscopy (SPM) techniques, including atomic force microscopy (AFM), made it possible to investigate certain aspects of materials characterization, which had been troublesome earlier [27–31]. Further scientific develop- ment allow to combine the AFM with the localized impedance spectroscopy measurements [32–36]. Thus, it was possible to investigate electrochemical and corrosion phenomena in detail [37,38]. The aim of this work involves differentiation between mechan- ical and electrical properties of two-phase alloys with significantly various particular phases by means of dynamic impedance spec- troscopy in the AFM contact mode. Therefore, it was possible to http://dx.doi.org/10.1016/j.jallcom.2014.08.214 0925-8388/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +48 58 3486396; fax: +48 58 3471092. E-mail address: anna.arutunow@pg.gda.pl (A. Arutunow). Journal of Alloys and Compounds 619 (2015) 172–176 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom