This work investigates the response of amorphous ribbons to shot peening using glass particles. XRD studies were carried out on treated and untreated ribbons and the change in peak positions were estimated. Elastic strains in the ribbon were calculated using peak shifts. Change in curvatures and thicknesses were measured. Several peening pressures were investigated and the change in mechanical properties including elastic modulus and strength were measured before and after peening. 13.2 Materials and Methods Amorphous Fe45Ni45Mo7B3 ribbons of 29 μm thickness and 50.8 mm width were used in this study. Owing to surface chilling in manufacture of the ribbon, one side of the ribbon had a reflective surface and the other a matte surface. Ribbon samples were peened on both sides by holding them on plates made of 50.8 mm wide Aluminum 2024, secured on a stainless steel template. The reflective side was treated first in all of the samples followed by treatment of matte side. Peening was performed in an enclosure1 equipped with a reclaimer and a dust bag. Glass beads of the type BT-8 were used as the impact media (0.15–0.2 mm in diameter). Several pressures were used for treating the ribbons from a 114 mm nozzle distance. With a significant curvature observed, the ribbon’s response for a pressure of 0.48 MPa (70 psi) is of interest in this study. Untreated and peened ribbons were etched using a 3 % Nital solution to observe a change in curvature. X-ray diffraction (XRD) measurements were also conducted on ribbon samples. All were treated using the two conditions shown in Fig. 13.1a: (1) untreated, (2) on the curvature (denoted as “peened”) after peening. X-ray diffraction2 was performed with Cu-Kα radiation at tube parameters of 40 kV/40 mA. The detector distance to the center of diffraction was kept at 30 cm, which covers approximately the area of 20 in 2θ and 20 in χ with 0.02 resolution. A motorized five axis (X, Y, Z (translation), χ (tilt), φ (rotation)) stage was used to move the measurement spot to the instrument center within 12.5 μm position accuracy. Sample positioning was controlled by a video-laser positioning system before each exposure to ensure diffraction patterns come from the impact treated regions of the ribbon. Samples for tension testing were prepared from peened samples of 50.4 mm width. A total of four samples were prepared for bulk tension tests, with each sample 12.5 mm wide. Tension tests were performed using a hydraulic driven Instron UTM. ASTM E345—93(2008) “Standard Test Methods of Tension Testing of Metallic Foil” was followed. Aluminum tabs were glued to the ribbon test specimen ends to avoid slipping from the grips. Applied strain was computed using a Laser Extensometer3 along with a data-logger suitable for recording compliance free strain measurements. Micrographs on the ribbon surface and thickness measurements were taken using a field emission scanning electron microscope (FESEM)4 equipped with a back scatter detector and EDAX system. The mass of the ribbon to 0.01 g accuracy was measured before and after peening. Aluminum plate Stainless Steel 316 plate Tape holding down the ribbon Peened area Amorphous Fe45Ni45Mo7B3ribbon Peened areas a b Fig. 13.1 Schematic of the Peening set-up. (a) Condition used for observing multiple curvatures, (b) Condition used to evaluate effect of peening on mechanical properties using tension testing 1Zero INEX 3048R. 2Bruker D8 Discover XRD2 micro-diffractometer equipped with the General Area Diffraction Detection System (GADDS) and Hi-Star 2D area detector. 3Model LE-05. 4Hitachi S4800-high resolution. 100 B. Jayakumar et al.
RkJQdWJsaXNoZXIy MTMzNzEzMQ==