Search Results (3,779)

This review examines hydrogen embrittlement (HE) in precipitation-hardenable aluminum alloys, focusing on the role of precipitates as hydrogen traps. It covers hydrogen entry mechanisms, the effects of microstructural features such as dislocations and grain boundaries, and secondary phase evolution during heat treatment. The interaction between hydrogen and precipitates, including the role of coherent and incoherent interfaces, is analyzed in view of the impact on HE susceptibility. Various techniques used to assess the interaction between hydrogen and aluminum alloys are also compared. The goal is to summarize the state-of-the-art understanding of the microstructural factors influencing the resistance of aluminum alloys to HE. Full article

In the project work, CES EDUPACK material selection software and Arc melter 500 arc remelting equipment were used to select good-performance materials and produce a sample. First, aluminum alloys were considered due to their low weight; alloys Al7075, Al6082, and EN AW 6022 in different states were examined for maximum hardness and electrical conductivity, and then the Cu–Cr–Zr alloy was analyzed. The test results showed that for the EN AW 6082 alloy, the specimens heat-treated at 480 °C for 2 h + 175 °C for 2 h following the ECAP (equal channel angular pressing) A route or C route technique gave the best hardness–electrical conductivity pair. In the case of the EN AW 7075 alloy, the artificially aged sample after 4× ECAP forming showed the maximum values. In the case of EN AW 6022, which according to the Ashby chart may be the best alloy for the value pair sought, this alloy was fabricated, resulting in only as-cast samples being analyzed. Of the Cu alloys, the Cu–0.49–0.21Zr alloy after heat treatment at 450 °C for 1 h gives the most favorable hardness–conductivity. Full article

SS 316L, a low-carbon 316 Stainless Steel, has been used to manufacture swivel mechanisms for paraplegic patients, but its weight is relatively high compared to a few materials in its range of properties. Aluminum alloy 6061 and Titanium alloy (Ti6Al4V) offer lightweight and incredible strength-to-weight ratio, hence their use for medical, aerospace, and automotive applications. This study, therefore, seeks a replacement for SS 316L. A 3D model of a swivel mechanism was developed to compare the performance of the swivel mechanism made with SS 316L, AA 6061, and Ti6Al4V. The kinematic analysis of the mechanism based on a range of weights: 1kN, 1.1 kN, 1.2 kN, 1.3 kN, 1.4 kN, and 1.5 kN was carried out to generate the inputs for the simulation. The 3D model was made with SolidWorks, and the results of the kinematic analysis were used to define the simulation parameters for the mechanism. Two scenarios generated depicted the full collapse of the mechanism and the full extension. The results showed that AA 6061 and Ti6Al4V outperformed SS 316L with higher yield strength and factor of safety. Therefore, swivel plates made with AA 6061 and Ti6Al4V have higher yield strength than those made with SS 316L, adding to the advantage that they have a higher strength-to-weight ratio. From this analysis and known knowledge of the cost of these materials, the optimal replacement considering cost with yield strength is AA 6061. However, Ti6Al4V is a better alternative for the strength-to-weight ratio for SS 316L. Full article

Gleeble thermomechanical simulators are widely utilized tools for the investigation of high-temperature deformation behavior in materials. However, temperature gradients that develop within the specimen during Gleeble compression tests have the potential to result in non-uniform deformation, which may subsequently impact the accuracy of the measured mechanical properties. This study presents an experimental and numerical investigation of the temperature fields in 2017-T4 aluminum alloy specimens prior to Gleeble compression tests at temperatures ranging from $300 °\mathrm{C} \mathrm{to} 500 °\mathrm{C}$ utilizing uniform temperature distribution (ISO-T) tungsten carbide anvils. The use of multiple thermocouples, welded to both the specimen and anvils, offers valuable insights into the temperature gradients and their evolutions. A coupled thermal–electrical finite-element model was developed in Abaqus for the purpose of simulating the resistive heating process. A user amplitude subroutine (UAMP) is implemented to regulate the heating based on a proportional–integral–derivative (PID) algorithm that modulates the current density to follow the specified temperature profile. The numerical results demonstrate that the temperature gradients within the specimen at the end of the heating process, reaching a temperature of $400 °\mathrm{C}$, are minimal, with values below $1.9 °\mathrm{C}$. This is in accordance with the experimental observations. The addition of graphite foils between the specimen and anvils has been shown to effectively reduce the gradients. The use of the measured anvil temperature as a boundary condition, rather than a constant value of $20 °\mathrm{C}$, has been demonstrated to improve the agreement between the simulated and experimental cooling curves. The modeling approach provides a framework for quantifying temperature gradients in Gleeble compression specimens and for assessing their impact on the measured constitutive response of materials at elevated temperatures. Full article

Press-hardened steels (PHS), as an alternative to traditional steels and aluminum alloys, combine great mechanical performance with low manufacturing costs. PHS are martensitic steels with ultimate tensile strength (UTS) up to 2000 MPa. These steels are commonly coated with zinc-based coatings (PHS GI) consisting of multiple Zn–Fe phases to enhance corrosion resistance. However, similar to all high-strength steels, PHS are known for their elevated susceptibility to hydrogen embrittlement (HE). Absorption of atomic hydrogen into the steel lattice can lead to a transition from a ductile to a brittle fracture mechanism and decrease the stress necessary for fracture initiation. This review examines the microstructure of PHS GI with a focus on how the manufacturing process influences key parameters of the coating. The material’s susceptibility to HE is discussed in the following sections, along with the potential for hydrogen introduction through corrosion in atmospheric environments. The relationship between the content of hydrogen and its effects on fracture behavior is discussed, along with the corrosion behavior of PHS GI. The potential areas for future research and development of PHS GI with increased HE resistance are proposed. Full article

In this study, the vitrification of asbestos-cement waste (ACW) and glass cullet from cathode-ray tubes (CRTs) was performed. The resulting product of vitrification from the abovementioned waste was used as the reinforcing phase in a composite with the AA7075 alloy matrix. The composite was made by means of the FSP (friction stir processing) method. The main aim of this work was to determine whether the product of the vitrification can be utilized as the reinforcing phase in the composite. The tests show that introducing the vitrification product into the composite matrix increases both the hardness of the material and its wear resistance. The composite was characterized by a 39% higher hardness and 30.4% higher wear resistance compared to the initial AA7075 alloy. The changes in the properties were caused by strong refinement of the grains, but primarily by the presence of the hard particles of the reinforcing phase in the composite matrix. This research demonstrates that vitrified material, thanks to its properties, can constitute a full-value reinforcing material that can ultimately replace more expensive engineering materials in composites. Full article

The surface quality of parts processed by laser additive manufacturing, especially laser-based directed energy deposition (LDED), makes it difficult to meet actual use requirements. In addition, defects generated during the long-term additive manufacturing process need to be removed in time. Therefore, laser additive and subtractive manufacturing is of great significance for additive manufacturing. The main difference between laser additive-subtractive manufacturing and pure subtraction is that a cooling temperature is required due to the laser process. Therefore, this work studies the temperature variation regularity during LDED and the milling processes, as well as the surface roughness, cross-sectional microstructure, and tool wear under different cooling temperatures for milling. The results show that there is a “turning point temperature” in LDED, and the value of the turning point temperature gradually increases with heat accumulation, which affects the initial temperature of the subtractive manufacturing. When subtracting, a high initial temperature improves surface quality and reduces tool wear, but an excessively high temperature will cause the aluminum alloy to adhere to the tool. Then, the smear metal is difficult to effectively remove, deteriorates the milling quality, and aggravates tool wear. It is found that the higher the cooling temperature generated, the wider the thermally insulated shear band. The insulated shear band may affect the quality of the additive and subtractive manufacturing. Finally, it is determined that the milling temperature of aluminum alloy in this work condition is about 100 °C. Full article

A series of chemical elements from the chemical composition of the packs of liquid food products migrate inside them or they combine with other chemical elements existing in the food, resulting in chemical compounds that worsen the quality of the food. In the present paper, layers of food stainless steel were deposited using thermal arc spraying on an aluminum alloy substrate to stop the migration of aluminum ions inside liquid food products. The physical-chemical and mechanical properties of the protection system: stainless steel layer used in the food industry (suggestively called: food-grade stainless steel)—aluminum substrate were investigated, and then the organoleptic properties of the food liquids that came into contact with the deposit were evaluated. It was found that food-gradestainless steel deposits have low porosity (3.8%) and relatively high adhesion and hardness, which allows complete isolation of the substrate material. The investigations carried out on the properties of food liquids that come into contact with the stainless steel deposit revealed the fact that it perfectly seals the aluminum start. The food-grade stainless steel coating (80T) was much better and safer for preserving dairy products maintaining a constant acidity up to 17 degrees Thorner, wines (with an average acidity of 3.5–4 degrees), juices (with natural pigments), and oils (with a good absorbance level correlated with clarity). This aspect suggests that the created system can be successfully used to manufacture containers for the transport of liquid products. Full article

Friction drilling is a non-conventional process that generates heat through the interaction between a rotating tool and a workpiece, forming a hole with a bushing. In this study, the effect of the preheating temperature, rotational speed, and feed rate on the induced temperature during the friction drilling of A356 aluminum alloy was investigated. This study aimed to analyze the influence of friction-drilling parameters on the thermal conditions in the induced bushing, where it focused on the relationship between preheating and the resulting heat generation. The analysis of variance (ANOVA) approach was carried out to optimize the friction-drilling parameters that contributed most to the induced temperature during the friction-drilling processing. Experiments were conducted at various preheating temperatures (100 °C, 150 °C, 200 °C), rotational speeds (2000 rpm, 3000 rpm, 4000 rpm), and feed rates (40 mm/min, 60 mm/min, 80 mm/min). The induced temperature during the process was recorded using an infrared camera, where the observed temperatures ranged from a minimum of 154.4 °C (at 2000 rpm, 60 mm/min, and 100 °C preheating) to a maximum of 366.8 °C (at 4000 rpm, 40 mm/min, and 200 °C preheating). The results show that preheating increased the peak temperature generated in the bushing during friction drilling, especially at lower rotational speeds. The rotational speed rise led to an increase in the induced temperature. However, the increase in the feed rate resulted in a decrease in the observed temperature. The findings provide insights into optimizing friction-drilling parameters for enhanced thermal management in A356 aluminum alloy. Full article

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS₂ composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS₂ coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10⁻⁶ mm/Nm. The MAO/MoS₂ coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS₂ enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries. Full article

This study fabricated (Al₆₃Cu₂₅Fe₁₂)₉₉Ce₁ quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the matrix and reinforcement was clear and intact. Chemical diffusion between the I-phase and aluminum matrix during sintering led to the formation of Al₇Cu₂Fe, AlFe, and AlCu phases, which, with their uniform and fine distribution, significantly enhanced the alloy’s overall properties. Regarding compactness, it first increased and then decreased with different holding times, reaching a maximum of about 98.89% at 490 °C for 30 min. Mechanical property analysis showed that compressive strength initially rose and then fell with increasing sintering temperature. After 30 min at 490 °C, the reinforcement particles and matrix were tightly combined and evenly distributed, with a maximum compressive strength of around 790 MPa. Additionally, the diffusion dynamics of the transition layer were simulated. The reaction rate of the reaction layer increased with hot-pressing temperature and decreased with holding time. Selecting a lower temperature and appropriate holding time can control the reaction layer thickness to obtain composites with excellent properties. This research innovatively contributes to the preparation and property study of such composites, providing a basis for their further application. Full article

Recent studies have proposed a simple formula, which is based on Elber’s original approach to account for R-ratio effects, for determining the crack closure-free ΔK_eff versus da/dN curve from the measured R-ratio-dependent ΔK versus da/dN curves. This approach, which is termed “Simple Scaling,” has been shown to collapse the various R-ratio-dependent curves onto a single curve. Indeed, this approach has been verified for a number of tests on metals, polymers, and a medium-entropy alloy. However, it has not yet been used to help assess/determine the closure-free ΔK_eff versus da/dN curve. The current paper addresses this shortcoming and illustrates how to use this methodology to assess the ΔK_eff versus da/dN curves given in the open literature for tests on a number of steels, aluminum alloys, STOA Ti-6Al-4V, a magnesium alloy, and Rene 95. As such, it would appear to be a useful tool for assessing fatigue crack growth. Full article

The present study examines the tribological behavior of an EN AW-4006 aluminum alloy subjected to two innovative hard anodizing processes involving the sealing of anodic oxide pores with Ag⁺ ions and tested in lubricated conditions. Four plant-based lubricants with different concentrations of fatty acids were considered. Wear tests were conducted using a ball-on-disk tribometer, employing a constant frequency oscillatory motion at 2 Hz and a maximum linear speed of 0.1 m/s. The investigation explores the influence of applied loads (5 N, 10 N, and 15 N) on the resulting coefficient of friction. Through a Design of Experiments methodology, the most influential factors affecting the coefficient of friction are identified. The results indicate that hard anodizing processes and applied load affect the coefficient of friction during wear testing as the main factor of influence. High values of the Unsaturation Number led to a high coefficient of friction at 5 N. Wavy-shaped profile tracks were detected at 10 and 15 N, leading to high specific wear rate values and the failure of the anodized layer. Full article

Metal matrix composites (MMCs) reinforced with Copper Oxide (CuO) and Aluminum (Al) 6061 (Al6061) alloys are being studied to determine their mechanical, physical, and dry sliding wear properties. The liquid metallurgical stir casting method with ultrasonication was employed for fabricating Al6061-CuO microparticle-reinforced composite specimens by incorporating 2–6 weight percent (wt.%) CuO particles into the matrix. Physical, mechanical, and dry sliding wear properties were investigated in Al6061-CuO MMCs, adopting ASTM standards. The experimental results show that adding CuO to an Al6061 alloy increases its density by 7.54%, hardness by 45.78%, and tensile strength by 35.02%, reducing percentage elongation by 40.03%. Dry wear measurements on a pin-on-disc apparatus show that Al6061-CuO MMCs outperform the Al6061 alloy in wear resistance. Al6061-CuO MMCs’ strength has been predicted using many strengthening mechanism models and its elastic modulus through several models. The strengthening of Al6061-CuO MMCs is predominantly influenced by thermal mismatch, more so than by Hall–Petch, Orowan strengthening, and load transfer mechanisms. As the CuO content in the composite increases, the strengthening effects due to dislocation interactions between the matrix and reinforcement particles, the coefficient of thermal expansion (CTE) difference, grain refinement, and load transfer consistently improve. The Al6061-CuO MMCs were also examined using an optical microscope (OM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) before and after fracture and wear tests. The investigation shows that an Al6061-CuO composite material with increased CuO reinforcement showed higher mechanical and tribological characteristics. Full article

Serrated flow effects are visible on a metal surface even after coating. Thus, they are undesirable to manufacturers and product users. To meet the expectations of the industry, research on the conditions for serrated flow occurrence in 5019 aluminum alloy was carried out and the results were collected in the current paper. Thus, the influence of the alloy initial microstructure due to different tempers as well as plastic deformation conditions, i.e., strain rate and temperature, on the alloy stress–strain behavior was determined. Two tempers were considered: the as-fabricated F-temper and the W-temper (i.e., quenched in water after annealing at 500 °C). The synergic influence of these tempers and their tensile test conditions on the serration behavior of the stress–strain curves, i.e., the stress drop and reloading time, were also determined and categorized. Structural and X-ray diffraction studies rationalized the stress–strain characteristics according to dynamic strain aging models with positron annihilation lifetime spectroscopy providing insight into the role of lattice defects (i.e., dislocations and vacancies). The map of the serrated flow domain allowed us to obtain the activation energy of the onset of the Portevin–Le Chatelier effect equal to 56 kJ/mol. It is close to the activation energy for the pipe diffusion mechanism, obtained by applying the model formulated originally for Type B stress serration. Full article