Journal of Alloys and Metallurgical Systems最新文献

A combination of physical modeling, computational fluid dynamics modeling, and economics with plant trial studies was performed for quality improvement of Special Bar Quality (SBQ) and Oil Country Tubular Goods (OCTG) grade tundish steels. The present study consists of operating parameters like inert gas shrouding, non-isothermal conditions, and flow control devices (FCD) used on the billet product and slab quality. This work uses mathematical modeling using the fluid volume and discrete phase method (DPM) and the standard k-ε turbulence model validated with one-third scale physical water model experiments. A strong correlation between the physical model and computational simulation was found with rejection ratio and inclusion counts. Data about customer demands correlated with operating parameters for proper plant insights with an economic study to predict the cost-related issue. With the incorporation of FCD, the weight of the tundish skull was reduced by 6–10 M USD/year with a simulation studies expenditure of around 200 K. FCD also reduced the customer complaint index (CCI).

Isothermal compression tests were executed on an Al-Mg-Si-Zr-Mn alloy using a Gleeble-3800 thermo-mechanical simulator at temperatures from 400 to 550 °C and strain rates ranging from 1 to 0.001 s⁻¹. By analyzing the flow curves and characterizing the deformed microstructure, this study aimed to gain insights into the hot deformation behavior and hot workability. Utilizing the hyperbolic-sine sinusoidal model, a constitutive equation was derived, revealing an activation energy of hot deformation of 274 kJ/mol. The processing maps were constructed utilizing the dynamic material model, which highlighted the secure range of hot working conditions between 480 to 550 °C and 0.01–0.001 s⁻¹. The softening mechanism observed at relatively low deformation temperatures and high strain rates was primarily dynamic recovery, whereas the safe domain exhibited a combination of dynamically recovered (DRV) and recrystallized (DRX) grain structures. The results of the FEM simulation indicated a non-homogeneous distribution of stress and strain fields, with the highest effective values focused at the center of the sample. Furthermore, the FEM simulation unveiled a clear correlation between the evolution of DRV and DRX and the strain.

An investigation was carried out to assess the suitability of equiatomic ZrNbVTiAl high-entropy alloy (HEA) for biomedical applications. This included microstructural analysis, mechanical property evaluation and in–vivo testing in biological media to examine its cyto-compatibility. The alloy developed a dendritic structure on solidification through arc melting, with BCC –B2 type dendrites separated by inter-dendritic regions rich in Al and Zr. The evolved microstructure and composition matched well with those predicted by the phase field modelling. The HEA also showed a high yield strength (1045 MPa) and moderate elastic modulus (120 GPa) comparable to the commonly used biomedical alloy, Ti-6Al-4 V. Cell culture studies with U2OS Cells showed substantial attachment and growth of healthy osteoblasts to the HEA as well as negligible bio-corrosion after 45 days of exposure. Most importantly, the alloy showed a significantly high tendency of cell attachment than pure Ti and lower magnetic susceptibility (2.55 ×10⁻⁶ cm³/g) than Ti-6Al-4 V alloy indicating its suitability for biomedical applications.

Low cycle fatigue (LCF) and ratcheting experiments were carried out on annealed low-carbon steel at room temperature within a laboratory environment, utilising stress and strain control modes. The annealed low-carbon steel consistently demonstrates a cyclic softening response over its LCF lifespan, across all tested strain amplitudes. Notably, it was observed that ratcheting strain rises while ratcheting life declines with both rising mean stress and stress amplitude. Annealed low-carbon steel, being entirely ferritic and lacking precipitation or substitutional solid solution strengthening or hard phase strengthening, exhibits a restricted ability to withstand or alleviate the accumulation of ratcheting strain, particularly under very low mean stress conditions. In both LCF and ratcheting, significant substructure formation was detected. Nevertheless, there was no discernible difference in substructure formation between LCF and ratcheting when employing electron channelling contrast imaging techniques. The existing mean stress-based fatigue life prediction model has successfully forecasted ratcheting and LCF life within the 10²–10⁵ cycles range. A novel approach utilising modulus is introduced to characterise the cyclic hardening/softening behaviour of alloys in stress and strain-controlled experiments. The cyclic hardening model based on modulus effectively captures the responses observed in cyclic hardening/softening during LCF and ratcheting experiments.

This research explores the tribocorrosion behaviour of 60NiTi alloy, also known as NiTiNOL60, when exposed to a saline environment. Our investigation focuses on understanding the relationship between corrosion and wear rates and assessing surface damage and material degradation. To conduct our experiments, we employed a linear reciprocating ball-on-plate tribometer coupled with electrochemical polarisation using a three-electrode cell configuration to assess the combined effects of corrosion and sliding wear. Surface characterisation was carried out through scanning electron microscopy and energy dispersion spectroscopy, revealing the material to be a Ni-rich 60NiTi alloy, with surface oxidation evident in the electrolyte medium. Our electrochemical findings indicate the occurrence of localised corrosion in both cathodic and anodic regimes, with corrosion pit nucleation, cavities, and cracks being accelerated by reciprocating sliding and corrosion potential. These interactions exposed the material surface to various wear mechanisms, including abrasive, adhesive, oxidative, corrosive, and fatigue processes. This study underscores the significant influence of mechanical properties on the rate of material degradation due to corrosion, while also highlighting the substantial impact of prevailing electrochemical conditions on the rate of mechanical material removal. This paper offers valuable insights for designers working on load-bearing structures in saline environments.

The exceptional high-temperature mechanical properties of Ni-based superalloys are mainly stemmed from the L1₂ γ' phase, therefore it is crucial to discover Ni-based superalloys with high γ' solvus temperatures. Utilizing generative artificial intelligence, we have developed a framework to swiftly evaluate the γ' solvus temperature and tailor Ni-based superalloys, accelerating the process of discovering Ni-based superalloys. Physics-informed artificial neural network emerged as the optimal choice for reverse engineering, outperforming other models with an R² score of 0.917 and a mean absolute error of 15 K. In the reverse design process, 20,000 virtual alloy samples were generated based on divide-and-conquer variational autoencoder which divides the dataset into distinct clusters by K-means algorithm provides a structured representation of the alloy composition space, thereby facilitating a more nuanced understanding of its inherent complexities. In a specific alloy design example, 563 samples were identified through screening based on criteria like γ' solvus temperature, composition deviation index, price, and density. Thermodynamic calculations were used to further screen Ni-based superalloys with exceptional high-temperature properties. The showcase of BA alloy discovery through generative artificial intelligence demonstrates the potential of our research to steer the creation of novel compositions for Ni-based superalloys with outstanding high-temperature properties.

Porous Ti-xNb-13Zr alloys (x = 13, 24, 35 mass%) have been synthesised from TiO₂-Nb₂O₅-ZrO₂ oxide discs by molten salt electro-deoxidation at 1173 K. The aim has been to assess the dependence of the alloys’ phase composition, microstructure, chemical homogeneity, oxidation resistance and corrosion resistance on their Nb contents. Phase analysis revealed that Ti-xNb-13Zr alloys with 13 and 24 mass% Nb were α/β-alloys, whereas the alloy with the highest content of 35 mass% had exclusively the β-structure. The alloys displayed significant open porosities of 50–54 %; particle size increased with increase in Nb content from 13 to 24 mass% and then decreased with further increase to 35 mass%; and the distribution of Ti, Nb and Zr was uniform. Thermokinetic examination of the alloys in air showed that the oxidation was slowest for Ti‐24Nb‐13Zr which was due to its comparatively larger particles. Open circuit potential measurements in Hanks’ simulated body fluid solution and surface spectroscopic characterisation of a long-term immersed sample indicated the formation of a passive oxide film and a hydroxyapatite layer on the surface. Overall, the study has brought out that the Nb content of the alloys has a crucial influence on all of the above properties.

Non-contact direct reduction (NDR) is an alternative technique in iron and steelmaking. Direct reduced iron production (DRI) uses it. To further harness the metallurgical and operational capabilities of the process for its suitability as an alternative feed in the blast furnace process, there is a need to study the effect of the reduction parameters on the weight loss, crack propagation level, gas porosity, iron whisker growth, and morphological characteristics of the DRI. Thus, this paper attempts to utilize the NDR process using commercially acquired goethite-hematite ore in a carbon-monoxide atmosphere from wood charcoal under specified isothermal conditions, with a reduction temperature range from 570, 800, and 1000 °C. The effect of reduction parameters on weight loss, crack propagation, iron whisker growth, and morphological properties of the DRI was investigated using standardized reduction reaction practices under a nitrogen gas atmosphere with a flow rate of 120 mL. Mineralogical and morphological analyses of the direct reduced iron (DRI) and charcoal were performed using XRF and SEM/ED analysis. Proximate and ultimate analyses of the reductant were performed to ascertain their physical and chemical properties. The results show that reduction parameters tremendously influence the weight loss, crack propagation, gas porosity level, and metallurgical quality of the DRI. The reduction degree and swelling extent of the DRI also increase with crack propagation and iron whisker growth. Thus, the overall reduction mechanism still follows the usual stepwise chronological reduction order (Fe₂O₃ → Fe₃O₄ → FeO → Fe) regardless of temperature, with ash layer control being the reaction rate control. The NDR technique shows no carbon deposition in the DRI metal matrix. It indicates that this approach can serve as a viable alternative for DRI production in the ironmaking process.

Titanium alloy (Ti-6Al-4V) is widely used in additive manufacturing (AM) industry. However, as laser powder-bed fusion (PBF-L) additive manufacturing (AM) advances towards reliable production of titanium parts, a thorough understanding of the process-structure-properties (PSP) relationships remain to be fully understood. A study of the laser melting was paired with high-speed X-ray synchrotron imaging at the 32-ID beamline of the Advanced Photon Source at Argonne National Laboratory. Simultaneous melting and imaging was carried out on a Ti-6Al-4V powder layer held in a custom device designed to mimic single-track scans of the PBF-L process at different laser power levels, powder size distributions, and cover gas environments (Ar and He) on top of AM Ti-6Al-4V base metal. It was found that the thickness of the powder layer significantly affected the melt behavior: too much powder led to the formation of molten droplets that wetted the surface of the titanium, yet did not contribute to a uniform melting profile. Residual gas pores in the atomized powder were also observed to contribute to the pores observed in the melt pool, with the porosity of the powder (defined as volume of pores divided by total material volume) constant with powder size distribution (i.e., larger particles contained more entrapped gas, which increased final part porosity). When varying Ar or He through the same gas flow meter settings and nozzle, the difference in flow rates likely contributed more to the resultant porosity of the solidified material than did the thermal conductivity of the gasses, with He being the greater contributor to porosity. The microstructure of the heat affected zone contained ${\alpha }^{\prime }$, α, and an increased β phase fraction relative to the base material. The crystallographic texture of the melt pool region adopted that of the base metal.

In this study, cold drawing 310 S stainless steel was selected as the raw material and employed two heat treatment methods, isothermal treatment (900°C for 12 hours) and thermal cycling processes (900°C-1 h↹room temperature-1 min-12 cycles and 900°C-1 min↹room temperature-1 min-100 cycles), to investigate the effects of heat treatment on the microstructural characteristics and mechanical properties. The results indicate that after isothermal treatment (900°C for 12 hours), the microstructure of AISI 310 S stainless steel transforms into a single-phase equiaxed grain structure. The strength decreases while the ductility increases. After thermal cycling treatment, the grain size is refined, resulting in increased strength but decreased ductility. Through FIB (Focused Ion Beam), WDS (Wavelength Dispersive Spectroscopy), and EPMA (Electron Probe Microanalysis) analyses, it was revealed that in a high-temperature, long-term environment, silicon (Si) tends to diffuse to the surface and aggregate with carbon (C) and oxygen (O) to form eutectic SiCO phase. These eutectic SiCO phase, upon melting at high temperatures and subsequent solidification after the experiment, result in the formation of shrinkage cavities in subsurface. Therefore, leads to the deterioration of tensile properties. On the other hand, after thermal cycling tests (900°C-1 min↹room temperature-1 min-100 cycles), due to thermal expansion and contraction inducing shear-induced defects in the lattice, the material exhibits recrystallization behavior, resulting in grain refinement and an increase in tensile mechanical properties. Additionally, conducting tensile strain analysis on the specimens after thermal cycling (two strain levels: 16%, 32%), it was observed that tensile cracks continue to propagate and grow along the surface cracks generated during the original thermal cycling, confirming the failure mechanism of thermal cycling.