Papers by Keyword: Aluminum Alloy

Abstract: Ultra-fine-grained (UFG) Al alloys have excellent mechanical properties such as high tensile strength without remarkable loss of elongation. Severe plastic deformation (SPD) process is an effective method for obtaining UFG microstructure. SPD-processed Al alloys has extremely high strength than the extrapolated from Hall-Petch relationship due to their microstructure with residual excess strain after dynamic recrystallization. Especially, on account of Al alloys have high stacking fault energy, the dislocation rearrangement in the dynamically recrystallized grain is difficult to form high angle grain boundary. As a result, there are substantial dislocation wall and low-angle grain boundary after SPD processing. These dislocations remain in the grain after recrystallization and partially form low-angle grain boundaries and subgrain boundaries. Consequently, the strength increases from Hall-Petch relationship, which is the degree of extra-hardening, was measured up to 200 MPa in as-SPD processed Al-3%Mg alloy. The authors previously reported that the low-angle grain boundaries distributed in the microstructure after the repetitive equal-channel angular extrusion processing. The strength difference calculated by Bailey-Hirsch equations was not in accord with measured extra-hardened strength. In this study, the effect of grain boundary distributions on the extra-hardening was investigated by changing SPD-processing and subsequent annealing conditions.

Abstract: This study investigates the degradation of adhesion between aluminum alloy and epoxy resin under high-temperature and high-humidity conditions. As next-generation power modules increasingly demand enhanced reliability, understanding the factors that affect metal/resin adhesion has become crucial. In this work, fourier transform infrared spectroscopy and adhesion strength testing were employed to evaluate the chemical and mechanical changes occurring at the interface during accelerated aging. FT-IR analysis revealed that the peak intensity of the carbonyl C=O peak in the epoxy resin decreased with aging time, while the aromatic C=C peak remained largely unchanged. The degree of moisture absorption, calculated from the ratio of these peak intensities, increased with the progress of aging. In addition, moisture uptake was found to weaken hydrogen bonding at the A1050/epoxy resin interface, and this effect was more pronounced in specimens with thinner resin layers. Adhesion strength tests showed a significant reduction in adhesive strength with prolonged exposure to high humidity and temperature. Fracture surface observations further indicated a shift in failure mode from cohesive to interfacial with aging. These results suggest that moisture-induced chemical changes at the interface contribute to the degradation of adhesion.

Abstract: Microstructural evolution during D.C. casting and subsequent homogenization of non-heat-treatable aluminium alloys involves complex phenomena, including micro-segregation of alloying elements and intermetallic phase selection during solidification as well as phase transformations of both primary (constituents - intergranular) and secondary (dispersoids - intragranular) intermetallic phases. In this study, we simulated the microstructural evolution of AA3003 using a CALPHAD-based modelling framework implemented in ThermoCalc®. The framework integrates a Scheil-Gulliver solidification model coupled with a 1-D micro-segregation alleviation and diffusional phase transformation model (DICTRA®) and a Kampmann-Wagner Numerical (KWN) model for dispersoid precipitation (TC-PRISMA®). According to this approach, the development of a robust computational methodology is aimed at accurately predicting the influence of homogenization cycles on dispersoid precipitation, which in turn affects recrystallization behaviour via the well-known Smith-Zener drag phenomenon. Additionally, these CALPHAD-based simulations facilitate the assessment of impurity content effects on dispersoid precipitation, considering the increasing use of scrap in the fabrication of non-heat-treatable aluminium alloys. Furthermore, they provide precise estimates of Smith-Zener pinning forces as inputs for downstream mesoscale full-field process models, contributing to a holistic through-process modelling approach.

Abstract: In the present work artificial neural networks (ANN) models have been implemented and trained as surrogate models to replicate two physics-based microstructure models for Al-alloys, i.e. the ALFLOW model, which predicts the sub-structure evolution and associated flow stress during plastic deformation and the softening model ALSOFT, which predicts the softening behavior after hot/cold deformation, in view of the combined effect of recovery and recrystallization. Input for both ANN models was limited to variables such as strain, strain rate, time, temperature and solute concentration, and the flow stress as the output. Accuracy and efficiency were tested for different ANN architectures. It is demonstrated that fully connected feed-forward neural network architectures with ∼3 hidden layers are suitable as surrogate models for both ALFLOW and ALSOFT, with a potential speed-up of ∼100x for ALFLOW and ∼10x for ALSOFT.

Abstract: A melt drag twin-roll caster (MDTRC) was designed to convert vertical burrs at strip edges to horizontal burrs. A prototype MDTRC was assembled and tested. The forming roll is inclined frontward relative to the top of the solidification roll. Aluminum alloy strips were cast at a higher roll speed and lower roll load than what can be achieved with the conventional twin-roll caster for aluminum alloys. A semisolid layer which exists on the solidifying layer by a lower roll was formed and solidified using an upper roll. In this study, the formability of the semisolid layer and formation of horizontal burrs were investigated.

Abstract: Pre-precipitate (cluster) strengthening is an integral aspect in the design of novel aluminum alloys. To investigate the impact of clusters on the strength of different aluminum alloys, Monte Carlo methods and the modified embedded atom method potential function were employed to simulate dilute aluminum-rich solid solutions, and these ten elements (silicon, magnesium, manganese, titanium, zirconium, chromium, iron, lithium, copper and nickel) were added as solute elements. The yield strength was evaluated and then the relationships among cluster size, cluster number, yield strength, and alloy compositions were analyzed. Finally, in the binary aluminum alloys the introduction of zirconium produces the largest yield strength among these ten elements, on the opposite side, the yield strength of Fe added alloy is the lowest. In most ternary aluminum alloys, after Mg, Zr and Li were added, the yield strength was increased compared to the results of the binary alloy, and the yield strength of Al-Li-Zr alloys is the largest in all ternary alloys. For multi-component aluminum alloy, the increase in type and number of elements resulted in fewer clusters, larger cluster size, and higher yield strength.

Abstract: In Al-Si alloy roll casting, the thickness of the foil and strip decreases as Si content decreases below 2 mass%, contrary to the expectation that the latent heat decreases as Si content decreases. This phenomenon was investigated experimentally using a melt spinning single roll caster, melt drag single roll caster, and vertical type high-speed twin roll cater. The results demonstrate that the peeling of the solidification layer influences the thickness of the foil and strip. The relationship between casting conditions and adhesion of the solidification layers was also investigated.

Abstract: This study focuses on the simulation and experimental validation of orbital laser welding for aluminum alloy tubes. The trials were conducted on the TRU LASER ROBOT 5020 system by TRUMPF, which features a 30 kg robotic arm, a diode-pumped disk laser with a beam quality of 8 mm*mrad, and a minimum output power of 4000W on the workpiece. Aluminium 6082 Tubes were mounted on a fixture attached to an integrated rotary table, and a series of tests were performed with varying levels of edge preparation accuracy and different laser beam parameters such as power and head linear speed. The simulation was carried out using Ansys Mechanical witch ACT toolkit heat source model. The thermocouple mesurments and metallographic tests was a key parameter used to validate the simulation results. The temperature distribution during welding was compared with simulation results to adjust the thermal properties of the material within the simulation model. The combined simulation and experimental analysis provide a framework for optimizing the laser welding process, enabling the reduction of costly experimental trials by simulating different parameter ranges.

Abstract: Aluminum alloy sheets are widely considered for manufacturing lightweight thin-walled structural components in the automotive and aerospace industries. However, the poor formability of the material at room temperature is still a technical challenge. Warm forming evolved as a promising technology where the sheet metal is deformed at elevated temperatures below the recrystallization temperature. Numerical modeling is vital in the modern scenario to better understand formability and to improve the designing of tooling for complex sheet components during warm forming. Hence, it is imperative to understand the accuracy of material models on formability predictions at elevated temperatures. This work presents the effect of three yield criteria, namely, von Mises, Hill-48, and Barlat-89, on the formability predictions of AA6082-O sheet at elevated temperature, say, 200 °C. Analytical necking-based Marciniak-Kuczynski forming limit diagrams (MK-FLD) at the elevated temperature were predicted by incorporating these yield models. The accuracy of predicted MK-FLDs was validated with experimental data. Furthermore, finite element (FE) modeling of limiting dome height (LDH) tests was performed using sample sizes that developed deformation modes towards biaxial, plane strain, and uniaxial modes. The effect of different yield models on the forming behavior was studied in terms of part depths and major surface strain distributions. The compatibility of yield criteria on accuracy in prediction was assessed by overlapping with the experimental data. It was demonstrated that Barlat-89 was best suited compared to Hill48 and von Mises yield models.

Abstract: Boring process, also referred to internal turning, is commonly used to machine critical features of landing gear components like struts, brackets, and main cylinders. Over the past years, extensive research efforts have addressed the stability of the process by developing instrumented boring bars and advanced monitoring techniques. However, although the surface integrity characteristics, particularly the residual stresses, are crucial for structural components, it hasn’t been considered and its evolution over the boring conditions still not well understood. Hence, the present paper proposes a comprehensive investigation on the effects of boring conditions on the surface integrity of the aluminum alloy 7175-T74 commonly used in landing gear components. A parametric analysis has shown that lower cutting forces and surface roughness can be achieved using a larger insert nose radius. It was also found that feed rate, cutting speed and depth of cut experienced strong interaction effects with the machining mode (dry/wet) regarding the resultant cutting force and surface roughness. Results have also shown that wet boring conditions generated compressive residual stresses. An optimal boring condition was obtained using Grey relational analysis (GRA) – Taguchi method. Further investigation is required to refine the obtained optimal machining condition by considering the GRA results and the parametric analysis outcomes.