Papers by Keyword: Mechanical Properties

Abstract: A cold roll-bonding (CRB) process is applied to fabricate a multi-layer Al sheet using AA5052 and AA6061 alloys. The rolling is performed for four-layer sheets in which AA5052 and AA6061 sheets are stacked alternately after surface treatments such as degreasing and wire brushing. The 4-layer sheets with a thickness of 8 mm were roll-bonded to 2 mm by rolling at total reduction of 75%. The as roll-bonded Al sheets are then processed by natural aging (T4) and artificial aging (T6) treatments. T4 and T6 treated specimens showed a typical recrystallization structure over all regions of AA5052 and AA6061. The average grain diameter of T4 and T6 specimens was about 15 μm, which is almost the same. In addition, the Al sheet showed a heterogeneous hardness distribution in thickness direction. After the aging treatments of T4 and T6, the strength rather decreased and the elongation increased. It is found that new multilayer Al sheets made of AA6061 and AA5052 alloys, exhibiting various mechanical properties can be fabricated through the CRB and subsequent aging treatments.

Abstract: Solid polymer electrolytes are recently investigated as alternatives to enhance the efficiency of lithium-ion batteries because of their inherent advantages. However, ionic transport through solid polymer electrolytes and mechanical properties of the electrolyte tend to be poorer compared with the liquid organic salt electrolytes. Granted, nanobased materials have attracted increased interest due to their ability to improve the properties of the electrolytes of lithium-ion batteries. This review is intended to highlight recent advances in utilizing nanomaterials in improving the electrochemical and mechanical characteristics of the solid electrolyte to enhance the performance of lithium-ion batteries. The synthetic techniques employed, as well as limitations of nanomaterials, are summarized. Recommendations for further development of novel functional nanomaterials for lithium-ion batteries are presented. Insight from this research will guide researchers in lithium battery technologies to make informed decisions, specifically when using nanobased materials.

Abstract: High-strength and recycling tolerable aluminum alloys make a significant contribution to weight reduction in modern lightweight construction. The advantages of aluminum alloys in terms of their low density combined with high strength can be significantly improved by the alloy composition. In contrast to the conventionally established process route, high-magnesium alloys can be produced using the twin-roll strip casting process. This allows additional process steps such as hot rolling and annealing to be drastically reduced in the economical production of near-net-shape strips, saving emissions and energy consumption. The strip casting process has already been applied to numerous aluminum alloys and enables their production, although the understanding of advanced alloys in this area is not yet fully understood because of its limited production in industry-related research due to the complexity of the process. However, transferring the high strength generated during rapid solidification into usable sheet performance remains challenging, especially at elevated Mg contents, where segregation, casting-related defects, and solute-affected recrystallization can limit ductility and processability. This study investigates the potential of a high-magnesium aluminum alloy produced by vertical strip casting. The properties of the alloy are correlated with the microstructural and mechanical characteristics and developed on the basis of an industrial reference alloy. For this purpose, an EN AW 5182 and an AlMg10 alloy were processed. The results show that high-magnesium alloys can be produced and processed using strip casting. In terms of the high-magnesium alloy, improved results can be achieved compared to the industrial EN AW 5182 alloy. Key findings: The strength of high-magnesium alloy is significantly above those of the EN-AW 5182 after strip casting enabling nearly 600 N/mm² tensile strength, but the final properties are below this potentially possible characteristic after strip casting, presumably due to non-ideal recrystallization and an insufficiently adapted process route including rolling and annealing parameters.

Abstract: The dendritic microstructure formed during solidification plays a critical role in determining the mechanical properties of aluminum castings. In particular, secondary dendrite arm spacing (SDAS) is strongly influenced by the cooling rate and is closely related to yield strength, ultimate tensile strength, and elongation. However, experimental validation of these relationships requires a consistent methodology for defining cooling rate and linking it to microstructural and mechanical measurements. In this study, an experimental framework was established to investigate the relationships among cooling rate, SDAS, and mechanical properties in aluminum castings. Casting blocks with different thicknesses were fabricated to obtain a wide range of cooling rates. Cooling curves were measured during solidification, and cooling rates were determined using the second derivatives of the cooling curves. SDAS measurements and tensile tests were conducted on specimens extracted from symmetric positions within the casting blocks to ensure equivalent thermal histories. The results showed that the cooling rate–SDAS relationship exhibited a linear trend on a logarithmic scale, consistent with previously reported correlations. Smaller SDAS values were associated with increased yield strength, ultimate tensile strength, and elongation. The agreement between the present results and literature data confirms the validity of the proposed experimental framework for correlating solidification conditions, microstructure, and mechanical properties of aluminum castings.

Abstract: The objective of the present research was to identify the mechanical properties of 3D-printed biocomposite parts and their variation with different natural fillers (olive wood and almond shell). The materials were produced by filament extrusion with 5% fiber content in the polylactic acid matrix, and the samples were fabricated using the Material Extrusion Additive Manufacturing process. 3D printed specimens underwent tensile and flexural tests to assess their mechanical properties. The results showed reductions of 5%-18% in the tensile modulus and 10%-38% in the tensile strength for olive wood-and almond shell-based PLA, respectively. The same trend was detected for the flexural properties, with a slight reduction of 2%-3% in the flexural modulus and 3%-5% in flexural strength.

Abstract: The utilisation of friction-induced solid-state recycling, methodically adapted to the CoNform process, facilitates the continuous production of semi-finished products. The material intended for recycling is conveyed continuously via a rotating wheel. The volume flow is influenced by fixed surfaces, deflections, and constrictions, thereby creating an asymmetrical flow profile. In order to effect a change in the mechanical properties of the semi-finished product, the material fed into the process can be modified. This enables the amalgamation of two alloys or the direct transition between them. The inhomogeneous flow conditions present within the tool give rise to the mixing of materials, thereby creating a graded multi-material zone. The multi-material zone was divided into different areas and traced back to the process conditions. Within the transitions, the connections between the alloys were examined, as well as the influence on the boundary layer. Material properties were determined for the individual areas and located along the length of the profile.

Abstract: Optimizing the performance and reliability of welding techniques for dissimilar aluminum (Al) to titanium (Ti) is a promising way to establish new applications in aerospace industry. Due to structural weight reduction, lightweight materials can help to minimize fuel consumption and save emissions. Solid-state welding technologies allow short joining cycles and metallurgical changes, residual stresses and severe intermetallic compound formation can be reduced by limited thermal exposure. Besides temperature and plastic deformation, intimate contact plays an important role for diffusion. In this work, AlMgSi alloys with systematic variations of Mg and Si alloying elements, were welded to Ti6Al4V (Ti64) by refill Friction Stir Spot Welding. The focus lays on the effect of Ti64 sheet surface roughness, varied by different surface preparations. Additionally, the influence of the plunge depth, the distance between the tool and the Ti64 sheet surface is analyzed. It was found that a reduced tool to interface spacing has a beneficial influence on joint integrity. Grinding trenches allowed better bonding compared to the pit-like surface structure generated by sandblasting, which led to an increase in mechanical lap-shear properties. Knurling the grinded surfaces resulted in high standard deviation, as most likely not the whole interface area was bonded. However, the partially outstanding properties showed that a beneficial effect can be expected due to mechanical interlocking mechanisms, when sufficient diffusion is ensured.

Abstract: High-entropy alloys (HEAs), owing to their exceptionally favourable strength–ductility balance, are regarded as promising candidates for applications in the energy, automotive, and aerospace industries. A defining characteristic of face-centered cubic (FCC) high-entropy alloys is their low stacking fault energy, which facilitates deformation via mechanical twinning and promotes the activation of transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) mechanisms. The present study focuses on the development of a heterostructured material composed of CoNiFeMn and (CoNiFeMn)₉₅Mo₅ alloys. Furthermore, the Erichsen cupping test was performed to assess the formability of the produced material and to evaluate its suitability for deep drawing applications.

Abstract: The growing use of extruded aluminum components in vehicle structures necessitates both strength and ductility to meet energy absorption requirements. In this study, a new compression calibration method for multi-chamber, hollow sections was developed with the aim of improving dimensional accuracy while enhancing the ductility of AA6061 extruded profiles. The influence of this method on mechanical properties was investigated through uniaxial tensile tests, three-point VDA bending tests, and axial crush tests. The uniaxial tensile test results revealed a reduction in the (logarithmic) strain at necking, while no significant changes were observed in yield and ultimate tensile strengths. On the other hand, the VDA tests showed a systematic increase in the normalized bending angle, indicating improved energy absorption characteristics. Visual inspection and the absorbed energy obtained by axial crush tests supported the findings in the VDA tests, indicating the compression calibration method enhances the crushability of extruded AA6061 profiles, although this improvement is not identified in standard tensile data. Overall, this work introduces a new, industrial calibration method for hollow extrusions that also enhances crushability.

Abstract: Functionally graded materials represent a promising strategy for locally optimizing component properties while reducing both economic and environmental costs. To date, no study has addressed the development of a compositional gradient between 316L stainless steel and Invar 36 using the Wire Arc Additive Manufacturing (WAAM) process, despite the strong potential of this material combination. Indeed, such a gradient would combine the very low coefficient of thermal expansion (CTE) of Invar 36 with the low cost and excellent chemical resistance of 316L stainless steel. A particularly relevant application for this type of gradient is the storage of hydrogen or liquefied natural gas, where tanks are subjected to severe thermal stresses due to cryogenic operating temperatures. In addition, these structures must withstand aggressive environments and hydrogen exposure, which can induce material embrittlement, while maintaining sufficient mechanical properties to ensure structural integrity during service. Designing an optimal gradient therefore requires a detailed understanding of how mechanical, thermal, and chemical properties evolve with chemical composition. This study provides a preliminary assessment of these evolutions. The results show that the addition of 15–25 wt.% Invar 36 to 316L leads to a reduction in microhardness and ultimate tensile strength (UTS), associated with the disappearance of ferritic and σ phases, while significantly enhancing ductility. At higher Invar 36 contents, microhardness increases and ductility decreases due to carbide formation. From a thermal standpoint, the CTE does not follow a linear trend: it remains high up to approximately 75 wt.% Invar 36 Nb, then decreases sharply as the ferromagnetic behavior characteristic of Invar becomes dominant. Corrosion resistance remains satisfactory for Invar 36 contents below 15 wt.%, whereas higher contents lead to reduced chemical performance due to chromium dilution. Overall, these findings establish clear criteria for selecting optimal compositions in the design of a 316L–Invar 36 compositional gradient. They provide an essential foundation for the development, via WAAM, of robust and high-performance functionally graded materials suitable for applications requiring high dimensional stability, good chemical resistance, and controlled costs.