Abstract This study investigates laser-assisted metal–plastic (LAMP) joining of polyamide 6 (PA6) to AISI 1018 low-carbon steel using a 1 kW fibre laser system. The individual and interaction effects of four key process parameters, laser power, scanning speed, defocus distance, and number of scans, on joint quality are examined using a central composite design of the response surface method. An empirical model is developed to correlate lap-shear strength with these parameters and validated through analysis of variance and additional experiments, confirming predictive reliability. Careful control of process conditions ensures balanced heat input and laser interaction time, enabling enhanced interfacial adhesion while limiting polymer degradation and thereby improving joint performance. A maximum lap-shear strength of 45.86 N mm −1 for the AISI 1018/PA6 joint, about 66 % of the tensile strength of 2 mm-thick PA6, is achieved using 900 W laser power, 35 mm s −1 scanning speed, 40 mm defocus distance, and two scan passes. Post-shear analysis reveals PA6 residues and elongated fibrils on the steel surface, confirming strong interfacial adhesion and load transfer. Failure modes exhibit both adhesive and cohesive characteristics, influenced by process parameters. These findings confirm LAMP joining as a reliable method for fabricating durable AISI 1018/PA6 hybrids with adequate joint strength.
Abstract Polylactic acid (PLA) is a promising biodegradable polymer for green engineering applications but suffers from inherent brittleness, moisture sensitivity, and flammability. Mechanical strength, water absorption, and flammability were evaluated in this study for neat PLA, 1 wt.% carbon nanotube-reinforced PLA (PLA/CNT), and PLA/CNT composites with 3, 6, and 9 wt.% Delonix regia ash (DRA), all produced using fused deposition modeling (FDM). Compared to neat PLA (40 ± 4 MPa), PLA/CNT recorded a 17.5 % enhancement in tensile strength (47 ± 3 MPa), whereas the DRA-filled composite with 6 wt.% DRA attained a 40 % enhancement (56 ± 2 MPa). Flexural strength also improved from 70 ± 2 MPa for PLA to 80 ± 3 MPa (+14.3 %) with CNT and 94 ± 1 MPa (+34.3 %) with 6 wt.% DRA. Water uptake reduced from 33 ± 1.3 % (PLA) to 22 ± 0.9 % (PLA/CNT) and 17 ± 0.5 % at 6 wt.% DRA. Flammability analysis yielded ignition delay times of 6.41 ± 0.31 s (PLA), 8.42 ± 0.22 s (PLA/CNT), and 10.27 ± 0.28 s (6 wt.% DRA), with corresponding flame spread rates of 59, 48, and 39 mm min −1 . Thermogravimetric analysis also verified improved thermal stability, with degradation onset shifting from ∼325 °C (PLA) to ∼335 °C (6 wt.% DRA) and char yields ranging from 1.8 % to 7.5 %. Scanning electron microscopy fracture surfaces of the 6 wt.% DRA composite showed significant crack deflection and particle pull-out, which is characteristic of strong interfacial bonding. In general, the hybrid PLA/CNT–DRA system with 6 wt.% DRA provides the best balance of mechanical, moisture resistance, flame retardancy, and thermal performance for high-performance green structural applications.
Optically transparent l-alanine doped potassium thiocyanate crystal of dimension 7 & times; 3 & times; 3 mm3 was grown by the slow evaporation solution technique. To confirm the cell parameters and the peak shifts of the reflecting planes, X-ray diffraction technique was used. The amalgamation of potassium thiocyanate in l-alanine has been qualitatively examined by Fourier transform infrared investigation. The UV - Visible absorption spectrum of samples was recorded in the range from 200 nm to 1,000 nm. The doped potassium thiocyanate crystal was found to have an enhanced optical framework compared to pure l-alanine with a cutoff wavelength of 238 nm and the Urbach energy was also calculated. The mechanical behaviour l-alanine potassium thiocyanate crystal was investigated using a Vicker's micro-hardness analyser and hardness parameters were estimated. The thermal stability of the grown crystal as revealed by thermogravimetric and differential thermal analysis was found to be 269 degrees C. The dielectric behaviour of the sample was studied, along with second harmonic generation efficiency measurement through the powder Kurtz method.
High-strength low-alloy steels were tempered followed by warm rolling at the same temperature (tempforming). The strengthening by tempforming significantly improved the low-cycle fatigue resistance with total number of reversals to failure below about 105. In contrast, the high-cycle fatigue resistance was less affected by tempforming strengthening, which gradually reduced due to dynamic recovery during fatigue tests.
Magnesium (Mg) alloys are promising candidates for biodegradable orthopedic implants due to their mechanical compatibility and biocompatibility; however, rapid corrosion and hydrogen gas evolution in physiological environments limit their clinical application. This study presents a green, biocompatible coating strategy using a polymer-herbal composite of polyvinyl alcohol and neem (Azadirachta indica) extract, deposited on AZ31 Mg alloy via electrophoretic deposition. Electrochemical analyses, including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, demonstrated enhanced corrosion resistance for the 5 % polyvinyl alcohol-neem coating, with increased charge transfer resistance and improved surface stability. Contact angle measurements (n = 6) indicated slightly higher hydrophilicity for the 2 % coating; however, the difference was not statistically significant (p > 0.05), suggesting comparable wettability. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed uniform, crack-free coatings with successful composite deposition. No antibacterial activity was observed, likely due to limited release of bioactive compounds from the polymer matrix. Overall, the coating effectively modifies corrosion behavior and surface properties, indicating potential for controlled degradation and improved performance of Mg-based biodegradable implants.
