This paper aims to improve the mechanical properties and fatigue life of AISI/SAE 4140 alloy steel connecting rods (CRs). Conventional CRs are typically manufactured through open die forging/hammering, blocking, and hot forging processes. In the present work, a modification to the process route has been proposed such that the open die forging/hammering was completely replaced with a multistep asymmetrical reducer rolling technique. Four rolling passes were introduced to achieve the desired preform shape and size. The effect of each rolling pass on grain size, mechanical properties, and fatigue life was investigated. Samples from each multistep rolling, blocking, and forging stage were subjected to impact, hardness, tensile, and fatigue testing. Metallography using optical and scanning electron microscopes was also conducted to reveal metallurgical changes. Fatigue testing and fractography were performed using the R.R. Moore Rotating-Beam Fatigue testing machine and scanning electron microscope, respectively, to evaluate the fatigue life and the fracture behavior of both the conventional and multistep rolled forged CRs. It was observed that, unlike the conventional forging process, multistep asymmetrical rolling gradually reduces grain size as the rolling progresses and improves yield, tensile, and impact strengths, hardness, and ductility. In comparison to conventional forging, multistep rolling led to an almost 33% and 29% increase in yield and tensile strengths, respectively. Moreover, the fatigue life of multistep rolled CR increased by more than five times compared to conventional CR.

Commercially pure titanium (Ti) is widely used in bio-implants due to its high corrosion resistance. However, Ti exhibits marginally low mechanical and tribological properties, which limit its applications in some orthopedic implants. In this work, the Ti samples were subjected to ultrasonic surface mechanical attrition treatment (SMAT) for various durations to improve their surface properties such as hardness, strength and surface energy. SMAT-induced grain refinement was analyzed using optical, scanning electron and atomic force microscopy techniques. A Vickers hardness test was performed to determine the through-thickness hardness. Mechanical testing was carried out to measure the yield strength, ultimate tensile strength and ductility of the specimens. Corrosion tests were performed on a Gamry Potentiostat. The surface energy of SMAT-modified samples was calculated using the Owens–Wendt method. It was observed that SMAT reduced the average grain size from 50 μm to as low as 100 nm. The grain refinement and the corresponding grain boundary density led to a significant improvement in mechanical properties and biocompatibility in terms of increased hardness, yield and tensile strengths, surface energy, corrosion rate and hydrophilicity.

Natural soil (NS)-based geopolymers (GPs) have shown promise as environmentally friendly construction materials. The production of ordinary Portland cement is known to release significant amounts of greenhouse gas (CO₂) into the atmosphere. The main objective of this work is to synthesize a geopolymer (GP) from an uncommon aluminosilicate-based NS and a sodium silicate (SS) activating solution that would not only minimize the emission of harmful gases, but also offer improved mechanical strength. Samples of different compositions were produced by varying the wt.% of NS from 50% to 80% and adding a balancing amount of SS solution. The drying and curing of the samples were carried out in an electric oven at specific temperatures. The degree of geopolymerization in the samples was measured by Fourier transform infrared spectroscopy, and microstructural analysis was performed using a scanning electron microscope. Mechanical tests were conducted to evaluate the range of compressive strength values of the prepared GP samples. A minimum compressive strength of 10.93 MPa at a maximum porosity of 37.56% was observed in a sample with an NS to SS ratio of 1:1; while a ratio of 3:1 led to the maximum compressive strength of 26.39 MPa and the minimum porosity of 24.60%. The maximum strength (26.39 MPa) was found to be more than the reported strength values for similar systems. Moreover, an improvement in strength by a factor of three has been observed relative to previously developed NS-based GPs. It may be inferred from the findings that for the given NS, with almost 90% aluminosilicate content, the extent of geopolymerization increases significantly with its increasing proportions, yielding better mechanical strength.

Lead-based piezoelectric materials cause many environmental problems, regardless of their exceptional performance. To overcome this issue, a lead-free piezoelectric composite material was developed by incorporating different percentages of carbon fiber (CF) into the ceramic matrix of Bismuth Sodium Titanate (BNT) by employing the microwave sintering technique. The aim of this study was also to evaluate the impact of microwave sintering on the microstructure and the electrical behavior of the carbon-fiber-reinforced Bi_0.5Na_0.5TiO₃ composite (BNT-CF). A uniform distribution of the CF and increased densification of the BNT-CF was achieved, leading to improved piezoelectric properties. X-ray diffraction (XRD) showed the formation of a phase-pure crystalline perovskite structure consisting of CF and BNT. A Field Emission Scanning electron microscope (FESEM) revealed that utilizing microwave sintering at lower temperatures and shorter dwell times results in a superior densification of the BNT-CF. Raman Spectroscopy confirmed the perovskite structure of the BNT-CF and the presence of a Morphotropic Phase Boundary (MPB). An analysis of nanohardness indicated that the hardness of the BNT-CF increases with the increasing amount of CF. It is also revealed that the electrical conductivity of the BNT-CF at a low frequency is significantly influenced by the amount of CF and the temperature. Moreover, an increase in the carbon fiber concentration resulted in a decrease in dielectric properties. Finally, a lead-free piezoelectric BNT-CF showing dense and uniform microstructure was developed by the microwave sintering process. The promising properties of the BNT-CF make it attractive for many industrial applications.