Sandeep Sahu

This study investigates the microstructure, mechanical properties, and corrosion behavior of AlSi10Mg alloy fabricated via laser powder bed fusion (LPBF) and subsequently processed through high-pressure torsion (HPT), a severe plastic deformation (SPD) technique. HPT was conducted at various levels of strain, including quarter, half, one, five, and ten turns, all under a consistent pressure of 6 GPa at room temperature. Mechanical properties were assessed through microhardness and nano-indentation tests. Corrosion behavior was evaluated using open-circuit potential (OCP), potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS) electrochemical tests in a 3.5 wt% NaCl solution with 3.62 mg/L dissolved oxygen and a pH of 7 at 27 °C. Microstructure analysis revealed a progressive refinement of melt pools and cellular structures formed during LPBF as the number of HPT turns increased. This resulted in the elimination of porosity and an increase in the microhardness and nano-hardness of the alloy. Transmission electron microscopy (TEM) observations displayed the presence of uniformly distributed nanometer-sized grains after ten turns. Mechanical properties showed marked improvement, with microhardness increasing by approximately 50% and nano-hardness showing similar enhancement. Corrosion test analysis indicated that the corrosion resistance of the alloy did not show a significant improvement after HPT processing, except after five turns of HPT, where the corrosion resistance was indeed enhanced. This non-monotonic trend is attributed to microstructural inhomogeneity and the redistribution of eutectic Si and Mg ₂ Si phases, which impact the formation and stability of protective oxide films. The findings highlight that while HPT effectively refines the microstructure of LPBF-fabricated AlSi10Mg alloy and enhances mechanical properties, its effect on corrosion behavior is more complex and composition-dependent.

In this study, friction stir processing (FSP) is proposed for the treatment of AZ61 alloy, and an artificial neural network is built to predict and compare the experimental wear results. The effects of different processing parameters, including spindle speed (800–1200 rpm), traveling speed (5–15 mm min⁻¹), and depth of press (0.8–1.2 mm) on the microstructural evolution, mechanical properties, and wear behavior are investigated. Microstructural analysis reveals a grain size of 14 ± 2 μm for the FSP1 sample, with observed shifting of x-ray diffraction (XRD) peaks, indicative of texture development. Increasing spindle and traveling speeds increase the surface roughness, as observed by average roughness (Ra) values of 68.4 nm for a rotational speed of 800 rpm, traveling speed of 5 mm min⁻¹, and shoulder depth of 0.8 mm (FSP1) and 116.3 nm for rotational speed of 1200 rpm, traveling speed of 15 mm min⁻¹, and shoulder depth of 1 mm (FSP9). Microhardness values increase to 113.36 Hv for FSP1 and 79. 51 Hv for FSP9 compared to 65.92 Hv for the base material (BM) sample. The decrement in hardness from FSP1 to FSP9 can be attributed to increased heat input, resulting in coarse microstructure. Wear results show that FSP1 exhibits the lowest weight loss (0.003 g) and coefficient of friction (COF) (0.28) compared to other FSP conditions and BM samples (weight loss of 0.022 g and COF of 0.68). This work demonstrates the efficacy of friction stir processing in enhancing the wear resistance of magnesium alloys.

The tensile properties of an ultrafine-grained Al–9%Si–3%Cu alloy deposited by the laser powder bed fusion process have been investigated in this work. The additively manufactured (AM) alloy was subjected to high-pressure torsion processing at room temperature successfully at different number of turns in HPT and then inspected through hot tensile testing at 298 and 573 K using strain rates ranging from 10^–1 to 10^–4 s⁻¹. The processed alloy showed extensive refinement and high dislocation density that was associated with considerable strength at ambient temperature. The as-deposited and processed samples of the alloy exhibited significantly higher tensile strength and elongation under hot deformation conditions compared with their cast counterpart alloys. The room temperature-HPT processing presented ultrafine α-Al and well-distributed nanosized eutectic Si particles which significantly improved the tensile behaviour and thermal stability of the processed microstructures. The formation of fibrous structures has enhanced the flow behaviour and cavitation resistance at the elevated testing temperature. The current work indicates the impact of room temperature-HPT processing on the mechanical performance of the controllable AM-deposited alloy to meet industrial needs without further heat treatments or alloying additions.

Marine conditions are highly contentious for most materials manifested by the decayed condition of old ships and wrecks (made up of steel/wood). This work investigates the mechanical and corrosion behavior of aluminum-based composites reinforced with 3, 6, and 9 wt% of hybrid reinforcements (SiC, graphite, and ZrO ₂ ). It was observed that 3 wt% reinforcement composite had the optimum mechanical properties along with minimum corrosion rate. This composition had the least void contents, and its micro-hardness increased by 27.5% (42.6 VHN) in comparison to that of the unreinforced Al (33.3 VHN). Impact strength of the composite increased by 27.2% for 6 wt% hybrid reinforcement (247.1 J) and then started decreasing, whereas tensile strength of the composite increased by 8% for 9 wt% hybrid reinforcement (124.0 MPa) with respect to that of pure Al. The flexural strength of the pure Al reduced with the addition of hard reinforcing particles. The corrosion behavior of the composite was analyzed in 3.5% NaCl solution (simulating the seawater condition) at room temperature with the help of Tafel polarization curve and scanning electron microscopy (SEM) micrographs. It revealed that the 3% reinforced composite had the minimum corrosion current density (0.4 μ A) and corrosion rate (0.23 mpy) compared to those of pure Al. The surface morphology of corrosion tested samples indicated the pitting corrosion mechanism.