In this study the influence of varying twin-roll casting (TRC) conditions on the microstructure, texture and mechanical properties of a Mg-6.8Y-2.5Zn-0.4Zr alloy (WZ73) was investigated. In particular the twin-roll cast speed and rolling gap were varied. Post twin-roll casting, the microstructure exhibits non-uniformity across the strip thickness and consists of a network-like arrangement of the long period stacking ordered (LPSO) phases and the α-Mg matrix. The α-Mg matrix is characterized by dobulites (flake-like structures). Various defects typical for twin-roll cast strips were observed, along with a notable impact of casting conditions on the precipitation, morphology, and phase composition of the LPSO phases. The twin-roll casting speed significantly influences the resultant microstructural features. Higher casting speeds reduce the average equivalent deformation degree, leading to an increase in the phase fraction of LPSO structures but a reduction in thickness. Additionally, higher TRC speeds result in decreased solidification times, promoting inhomogeneity and segregation defects. These changes also impact the distribution of precipitates and strip temperature at the roll gap exit, delaying solidification and influencing centerline segregation thickness. Kink bands and yttrium-rich precipitates were present in all samples, with LPSO phases precipitating along grain boundaries. No dynamic recrystallization was observed. Texture analysis revealed basal and non-basal slip activation, with lower intensities at higher TRC speeds. The yield strength (YTS) and tensile strength (UTS) behaved similar whilst the elongation remained unchanged by the TRC conditions.
In the production of ductile iron, it is essential to control the chemical composition of melting, as this directly affects mechanical properties and final microstructure of the fabricated parts. However, this may not be sufficient. Physical phenomena such as nucleation potential, eutectic solidification, and recalescence provide useful information for production of ductile iron. Thermal analysis is a tool that has emerged to meet this need. In this study, thermal sensor equipment is employed to capture real-time samples of the molten metal to analyze its cooling curve. This information is used to determine physical state of the material during the various subprocesses required to produce ductile iron parts. Nucleation potential is the most influential thermal analysis property in ductile iron production. Controlling it helps assess the effects of nodularization and inoculation. Additionally, it plays a key role in optimizing costs and product quality. The high recalescence and solidification variability indicate a predominantly hyper-eutectic behavior, suggesting that reducing inoculant use could improve quality by preventing shrinkage defects, primary graphite formation, and carbides while lowering costs.
Christoph Kaden, Kristina Kittner, Madlen Ullmann, Ulrich Prahl
Twin-roll casting (TRC) enables the production of near-net-shape semi-finished products in a single forming step, offering significant energy and cost savings compared to conventional rolling. While TRC has been successfully applied to flat magnesium alloy products, its application to long products, such as wires, remains a novel research focus. In this study, the microstructure, texture, and mechanical properties of TRC wires were investigated for the common wrought alloys AZ31 and AZ80, as well as the calcium-containing alloy ZAX210. Microstructural analysis was performed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Mechanical properties were evaluated through tensile testing at room temperature. The TRC wires exhibited a central segregation zone with a characteristic necklace-like grain structure composed of small and large grains. The addition of Ca in ZAX210 significantly reduced segregation. SEM analysis revealed fine and large network-like intermetallic phases, including Mg 17 Al 12, AlMn, and Ca 2 Mg 6 Zn 3. Texture analysis indicated a pole split or a shifted basal pole with low intensities. Tensile testing showed that the increased Al content in AZ80 led to lower mechanical properties compared to AZ31. Both alloys displayed low elongation at fracture due to pronounced central segregation and brittle intermetallic phases. In contrast, ZAX210 exhibited a finer and more homogeneous microstructure, resulting in the highest tensile strength and elongation at fracture. These findings suggest that the TRC process introduces characteristic microstructural features that influence mechanical properties. The observed improvements in ZAX210 highlight the potential of calcium additions to refine the microstructure and mitigate segregation effects.
Jonathon Bracci, Kevin Kaufmann, Jesse Schlatter, James Vecchio, Naixie Zhou, Sicong Jiang, Kenneth S. Vecchio, Justin Cheney
Metal-based additive manufacturing offers potential to disrupt the manufacturing process across multiple industries. However, the vast majority of modern alloys are incompatible with the complex thermal histories of additive manufacturing. For example, the high gamma prime forming nickel-based superalloys are of considerable commercial interest owing to their properties; however, their gamma prime content renders them non-weldable and prone to cracking during additive manufacturing. Computational materials modeling and big data analytics is becoming an increasingly valuable tool for developing new alloys for additive manufacturing. This work reports the use of such tools toward the design of a high gamma prime superalloy with reduced cracking susceptibility while maintaining similar hardness to CM247. Experimental fabrication and characterization of the candidate alloys is performed. Results show the candidate alloys have improved printability, up to 41x reduction in crack density (mm/mm 2) compared with CM247, and good agreement with the modeled predictions.
J. M. Jáquez-Muñoz, A. N. Castrejon, M. A. Lira-Martínez, E. Maldonado-Bandala, J. Cabral-Miramontes, M. Lara-Banda, F. Estupiñán-López, D. Nieves-Mendoza, C. Gaona-Tiburcio, F. Almeraya-Calderón
For years, the aeronautical industry has employed different types of materials to satisfy its high-performance requirements. Fiber-metal laminates are used due to their combination of lighter weight and the high mechanical properties of reinforced metal and carbon. We therefore made two different composites of laminate-metal and laminate-metal-laminate of carbon fiber-reinforced polymer and aluminum with an ALCLAD layer. The samples were characterized by salt fog (0, 48, and 96 h) at 5 wt% NaCl and electrochemical impedance spectroscopy (EIS) with an electrolyte of 3.5 wt% NaCl. All samples were studied by electron scanning microscopy (SEM). The results demonstrated that the samples of laminate-metal-laminate presented an adsorption process after 0 and 48 h of salt fog exposition; meanwhile, the samples of laminate-metal showed a capacitive behavior for all the samples; however, corrosion resistance decreased when the salt fog exposition time increased.
