Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

Abstract

SummaryThe distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k * are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

Atomic force acoustic microscopy reveals the influence of substrate stiffness and topography on cell behavior

“…The deflections of the cantilever represent the morphological information, and the vibrations of the cantilever correspond to the acoustic signals. By employing a suitable mechanical model to describe the vibrations of the cantilever, the contact stiffness of the tip–sample interaction can be estimated [27–28]. For one-phase homogeneous materials, the detected vibrations will remain relatively uniform, while for inhomogeneous materials, the vibrational amplitude depends on the elastic properties and the AFAM image will reflect the stiffness changes [29].…”

Elasticity mapping of precipitates in nickel-base superalloys using atomic force acoustic microscopy

“…(2) can be eliminated provided that the measurements are carried out on a reference sample, for example, a single crystals or an amorphous material [44]. In case of polycrystalline materials, it has been successfully demonstrated that the matrix of polycrystalline materials can be used as a reference to determine the indentation modulus [36,38,39].…”

“…In the past two decades, AFAM has been extensively used to study elastic properties of metallic glasses [33], polymers [34], clay minerals [35], nickelbase superalloys [36,37], titanium alloys [38,39], composite materials [40], cement paste [41], single crystals [42], thin films [43], Pyrex glasses [43], etc. Even though numerous studies have been reported on elastic properties of various materials, very few experimental data are available on the elastic properties of precipitates present in structural alloys.…”

Advanced atomic force microscopy techniques III

“…Furthermore, physico-mechanical properties of intestinal cells were elucidated by force curve measurements by Eva Roblegg and co-workers [ 20 ]. The local elastic stiffness and damping of individual phases in a titanium alloys was measured by using atomic force acoustic microscopy (AFAM) and mapping of contact-resonance spectra [ 21 ]. Another alloy, namely a Pt containing metallic glass, was characterized by AFM indentation in UHV to quantitatively determine the hardness and deformation mechanisms by Arnaud Caron and Roland Bennewitz [ 22 ].…”