Friction-wear behavior of shot peened aluminium 7075-T651 alloy

20-26The present study reports the friction-wear behavior of un-peened and shot peened aluminium 7075-T651 alloy against aluminium 7075-T651 alloy in dry sliding condition. Shot peening was done using CI steel ball (40-45 HRC) with 0.6 mm diameter. Phase Structure, hardness, compressive residual stress, surface morphology and surface features are characterized using X-ray diffractometer (XRD), Vickers hardness tester, noncontact-surface profile meter and scanning electron microscope (SEM). Sliding wear test were conducted against aluminium 7075-T651 alloy in dry sliding condition at room temperature using a pin on disc apparatus. A 25% increase in the hardness was seen for shot peened aluminium 7075-T651 alloy. Shot peened aluminium 7075-T651 alloy has induced maximum compressive residual stress of -188 MPa. No new phases were formed for the shot peened aluminium 7075-T651 alloy, however, the shift in the plane is observed. There was also a drastically increase in surface roughness in spite of the peening process. Adhesive wear was the dominant wear mechanism for the un-peened specimen, whereas, it was reduced for the shot peened surfaces

Assessment on the impact of FSP process parameters on microstructural, mechanical and wear behaviour of FSPed AA6082

Abstract The present research work demonstrates the effect of friction stir process (FSP) and its process parameters (rotation speed and travel speed) on the microstructure evaluation, microhardness and wear behaviour of FSPed AA6082. The microstructure characterization of the processed samples was examined using the Optical Microscope (OM). Dry sliding wear test was carried out by varying the sliding velocity (0.5, 0.75 and 1.0 m s−1) and applied load (5, 10 and 15N) using the pin on disc apparatus. Wear mechanisms experienced by the FSPed AA6082 were mapped, and the optimal FSP and wear parameters have been determined using Taguchi analysis. The results showed that there is a significant improvement in the microhardness (92 HV 0.3) and wear resistance for RS 1250 rpm &amp; TS 40 mm min−1 due to the grain strengthening mechanism and microstructure modification. Formation of oxide layer played a crucial role on the wear resistance of the FSPed AA6082 and its significance has been discussed elaborately using the Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS).</jats:p

Detection of magnetic dipole lines of Fe xii in the ultraviolet spectrum of the dwarf star ε Eri

We report observations of the dwarf star e Eri (K2V) made with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. The high sensitivity of the STIS instrument has allowed us to detect the magnetic dipole transitions of Fe XII at 1242.00 and 1349 38 Å for the first time in a star other than the Sun. The width of the stronger line at 1242.00 Å has also been measured; such measurements are not possible for the permitted lines of Fe XII in the extreme-ultraviolet. To within the accuracy of the measurements the N v and the Fe XII lines occur at their rest wavelengths. Electron densities and linewidths have been measured from other transition region lines. Together, these can be used to investigate the non-thermal energy flux in the lower and upper transition regions, which is useful in constraining possible heating processes. The Fe XII lines are also present in archival STIS spectra of other G/K-type dwarfs