Journal of Alloys and Metallurgical Systems最新文献

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.

Due to strength and biodegradability, magnesium (Mg) and its alloys are potential biodegradable implant materials. However, pure Mg corrodes more rapidly in the physiological environment, causing rapid deterioration before bone repair. The discrepancy between bone healing and Mg implant deterioration encourages the development of new Mg alloys with other acceptable alloying elements to achieve the desired high corrosion resistance and mechanical properties. In this work, different concentrations of yttrium (Y), that is, Mg-4zn-0.2ca-xY, (x= 3,6,9,12% wt), are added to Mg-based alloys. The microstructure, mechanical characteristics, corrosion behavior, and biocompatibility of the alloys were carefully investigated. When Y concentrations are high, Mg alloys with Y change significantly. High Y concentrations in Mg alloys containing yttrium (Y) suppress intermetallic phases along grain boundaries and form chemically stable Y oxide layers on the surfaces, changing their microstructures and improving their corrosion resistance. Cytotoxicity analysis showed that human osteoblast cells were not significantly affected by the Y-containing Mg alloys. The benefits of using Y as an alloying element to simultaneously adjust Mg alloys with higher strength and slower deterioration are presented.

This study aims to investigate the dry sliding wear behaviour of AA-7075 based metal matrix composites developed by powder metallurgy route. AA-7075 metal matrix composites have been developed with 1–15 vol% micrometric yttrium oxide particulate reinforcement and 0.1–3 vol% nanometric yttrium oxide particulate reinforcement by sinter forging.The matrix and reinforcing powders were blended together to obtain a homogeneous composite powder mixture which was cold compacted and further sintered under pure nitrogen atmosphere. The sintered compacts were forged in a closed die to attain full density. The hot forged samples were further artificially age hardened to peak hardness. Wear behavior of AA-7075 and its composites at peak aged condition were investigated at various loads and sliding speeds. The coefficient of friction and wear rate were determined with respect to different volume fractions of micrometric and nanometric yttrium oxide additions to AA-7075 alloy matrix. The overall wear at a constant volume fraction was found to be lower for the compositions having nanometric Y₂O₃ as compared to micrometric Y₂O₃. Further the basic wear mechanism of pure aluminum 7075 alloy and reinforced composites consisted of adhesive wear with plastic deformation followed by abrasive wear (due to hard reinforcement particles).Material strengthening by precipitation hardening and reinforcement addition and the role of the forging operation and yttria reinforcements in the removal and uniform distribution of oxide layers present on the AA-7075 powder particles were accountable for the improvement in the wear resistance of the composites.

The AlSi10Mg alloy is one of the most studied alloys processed by the Powder Bed Fusion-Laser Beam (PBF-LB). Many already published works focus on post-process heat treatments to reduce residual stress or improve mechanical strength. Instead, the present study aims to identify direct artificial aging (AA) heat treatment able to optimize both aspects, thus enhancing the trade-off between strengthening and residual stress relief for the PBF-LB AlSi10Mg alloy produced using a no-heated platform. Higher temperatures (190–240 °C) than those typically used in AA heat treatment were selected based on thermal analysis to benefit both residual stress relief and precipitation of reinforcing phases from the supersaturated solid solution of the metastable as-built alloy. The effects of AA heat treatment on mechanical properties (i.e. hardness) and residual stress were evaluated by plotting aging curves and by XRD and Raman analyses and demonstrated that different trade-offs between strengthening and stress relief can be achieved by tuning heat treatment parameters (temperature and time). In particular, the exposure at the lowest temperature (190 °C) induced a partial decrease in residual stress and a slight increase in hardness. By increasing heat treatment temperature and soaking time, the relief was more significant, whilst the decrease in hardness was rather limited. The results are supported by the microstructural changes observed on the samples due to the different heat treatment conditions applied and show the feasibility of designing an AA heat treatment for the PBF-LB AlSi10Mg alloy capable of satisfying the mechanical response required by the final application.

This study investigated the interface microstructure that developed between 50In-50Pb (wt%) solder and copper (Cu) base material as a function of solid-state aging. The aging temperatures and times were in the range of 55°C – 170°C and 1 – 350 days, respectively. The analysis examined the intermetallic compound (IMC) layer compositions; the rate kinetics of IMC layer growth; and the role of the IMC layer on solder joint shear strength. The IMC layer transitioned from pseudo-equilibrium compositions towards an equilibrium composition of Cu₁₁In₉ (φ phase) with an increased degree of aging, illustrating the non-equilibrium nature of the interface. The rate kinetics for solid-state IMC formation exhibited a time exponent, n, of 0.47±0.09, which indicated a diffusion-controlled reaction. The relatively low, apparent activation energy, ΔH, of 23±4 kJ/mol implied an anomalously-fast diffusion mechanism. The shear stresses were 22±2 MPa and 19±1 MPa for the 0.190 mm and 0.380 mm joint clearances, respectively, representing the as-fabricated condition; the difference reflected the plane strain effect. The crack path remained in the In-Pb solder so that the In-Pb microstructure, not the thickness, composition, or morphology of the IMC layer, controlled shear strength for either joint clearance. The shear strength trends differed between joint clearances due to competing processes in the In-Pb solder. Precipitation and re-solutionization of Cu dissolved in the In-Pb solder controlled the effects of aging on the shear strength of the 0.190 mm joint clearance while traditional recovery and recrystallization mechanisms determined the aging response of the 0.380 mm solder joints.

The effect of austenitizing temperature (ranging from 850 to 1050 °C) and cooling rates on the phase transformations were investigated, particularly when a two cooling steps protocol was adopted. It was possible to observe that the heat treatment parameters play a major role on the martensitic transformation kinetics a possible occurrence of bainitic transformation. The results indicate that a microstructure composed by small austenite grains and the formation of bainite prior the athermal martensitic transformation significantly contribute to increase the martensitic transformation rate. The Koistinen-Marburger model was employed to analyze the non-isothermal kinetics, revealing an increase in the KM and k parameters due to an increase in austenite grain size and the presence of bainite in the microstructure. The results herein demonstrate that the optimization of the heat treatment parameters is crucial to the proper control of the phases that will be present in the microstructure of the alloy, as well as the volume fraction of martensite. Thus, the accurate control of the heat treatment process is a promising approach to enhance the properties of SAE 9254 spring steel, which finds extensive use in the automotive industry.