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Abstract Additive friction stir deposition (AFSD) is a novel additive manufacturing technique that enables the fabrication of components in the solid state. Given the benefits of AFSD, understanding the behavior of various feedstock materials after undergoing the AFSD process is crucial for optimizing their performance in structural applications. This study aims to evaluate the effects of AFSD on an Al–Mg alloy, Al5086, comparing it to its initial H32 condition to assess the changes in mechanical properties, microstructure, corrosion resistance, microhardness, and electrical conductivity. Tensile testing showed a 23% reduction in yield strength for as-deposited samples, while ultimate tensile strength remained comparable to the feedstock. Ductility improved significantly, with elongation to failure increasing by 77%, attributed to grain refinement and dynamic recovery. Microhardness decreased by 16% in lower layers due to thermal exposure, but electrical conductivity remained stable, indicating minimal solute atom redistribution. The Nitric Acid Mass Loss Test (NAMLT) revealed a 245% increase in corrosion rate for the AFSD material, linked to the higher density of grain boundaries acting as pathways for corrosion. These findings highlight AFSD’s potential for improving ductility and formability. However, they underscore the need for optimization to reduce corrosion susceptibility and address mechanical strength trade-offs. Future work should focus on fine-tuning process parameters or implementing post-treatment methods to enhance corrosion and mechanical performance. 

Abstract Additive Friction stir deposition (AFSD) has been extensively utilized for processing Al alloys. The properties of the Al depositions under as-fabricated state, including mechanical strength and corrosion resistance, are typically inferior compared to the base material, especially for heat-treatable alloys. In this research, multilayers of Al7075 composites, reinforced by ceramic particles, were processed by AFSD to evaluate the effect of using feedstock materials containing reinforcing particles on the properties of the deposition. For comparison, a bare Al7075 part was also processed by AFSD under the same conditions. The results of mechanical testing revealed a significant reduction in the microhardness, tensile strength and compression stress of the bare alloy after deposition. However, the composite deposition exhibited only a slight decrease in the properties compared to its feedstock material. Additionally, the corrosion resistance of the composite enhanced after AFSD, in contrast to the bare alloy, where the corrosion resistance deteriorated. Microstructural analysis showed a uniform distribution of the reinforcing particles in the matrix for the deposition, closely resembling that of the feedstock composite. This, along with grain refinement and minimal change in precipitates, were the reasons for the minimum changes in mechanical properties, as well as the improvement in corrosion resistance. 

Abstract Four different experimental approaches for rapid estimation of fatigue limit (endurance limit) based on energy dissipation during cyclic loading are discussed. The presented approaches use energy dissipation and thermography and can reliably evaluate the fatigue limit of material by conducting the fatigue test on a single specimen. Results show that the released energy due to damage accumulation at the stress levels above the fatigue limit changes the trend of energy dissipation and that this trend can be used to predict the fatigue limit. Experimental results on CS 1018 and SS 304 specimens are presented to illustrate the utility of the proposed methods. 

Abstract Building S-N curves for materials traditionally involves conducting numerous fatigue tests, resulting in a time- consuming and expensive experimental procedure that can span several weeks. Thus, there is a need for a more efficient approach to extract the S-N curves. The primary purpose of this research is to propose a reliable approach in the framework of thermodynamics for the rapid prediction of fatigue failure at different stress levels. The proposed method aims to offer a simple and efficient means of extracting the S-N curve of a material. A method is introduced based on the principles of thermodynamics. It uses the fracture fatigue entropy (FFE) threshold to estimate the fatigue life by conducting a limited number of cycles at each stress level and measuring the temperature rise during the steady-state stage of fatigue. An extensive set of experimental results with carbon steel 1018 and SS 316 are conducted to illustrate the utility of the approach. Also, the efficacy of the approach in characterizing the fatigue in axial and bending loadings of SAE 1045 and SS304 specimens is presented. It successfully predicts fatigue life and creates the S-N curves. The effectiveness of the approach is evaluated successfully for different materials under different loading types. The results show that the temperature rise is an indicator of the severity of fatigue and can be used to predict life. 

Solid-state additive friction stir deposition (AFSD) is a thermomechanical-based additive manufacturing technique. For this study, AFSD was utilized to produce aluminum alloy 6061 (AA6061) blocks with varying layer thicknesses (1 mm, 2 mm, and 3 mm). The mechanical properties were assessed through uniaxial tensile tests and Vickers microhardness measurement, and statistical analysis was employed to investigate differences among data groups. The results revealed that the deposition layer thickness influences tensile properties in the building (Z) direction, while the properties in the X and Y directions showed minor differences across the three AFSD blocks. Furthermore, variations in tensile properties were observed depending on the sample orientation in the AFSD blocks and its depth-wise position in the part in the building direction. The microhardness values decreased non-linearly along the building direction, spread across the width of the part’s cross-section, and highlighted that the deposition layer thickness significantly affects this property. The 1 mm block exhibited lower average microhardness values than the 2 mm and 3 mm blocks. The temperature histories and dynamic heat treatment are influenced by the deposition layer thickness and depend on the location of the point being studied in the part, resulting in variations in the microstructure and mechanical properties along the building direction and across the part’s width.