Metals and Materials International最新文献

The present study aims to investigate the influence of reinforcement filling strategy on particle distribution and mechanical properties of ZA27/TiH₂ composites fabricated through friction stir processing. For comparison, the base material and processed material without reinforcement were considered as reference materials. In this work, the parameter which was taken as a variable, was reinforcement filling strategy. The microstructures were analyzed using optical and scanning electron microscopes. Microhardness, tensile, and wear tests were also performed. Microstructure analysis showed the particle distribution in hole-filling methods is more uniform than groove-filling methods. Besides, among hole-filling methods, those which contained more holes with smaller diameters exhibited more homogenous particle distribution and fewer defects. Further characterization revealed that the mechanical properties of the linear pattern were higher than the zigzag pattern and even the base material, so the failure occurred in the base material. However, the mechanical properties of other composites such as hardness, strength, and elongation were found lower than reference materials due to the agglomeration of particles. The wear test results showed that the wear resistance of the unreinforced FSP sample decreased as compared to base material whereas improved by adding reinforcement particles into two linear rows of blind holes.

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This study focused on the fabrication and characterisation of TiO₂/Graphite reinforced Cu-based composite produced by powder metallurgy. The effects of varying amounts of TiO₂ combined with 2% (w/w) graphite on the wear and corrosion behavior of stoichiometric copper (Cu) were investigated using various characterization techniques. The phase analysis revealed that Cu was the main phase. At low doping ratios, graphite peaks were found in trace amounts, while rutile phases of TiO₂ were detected. The microstructure and phase properties of the produced matrix and fracture surfaces were examined by scanning electron microscopy. As a result of the measurements made with the Vickers hardness tester, it was observed that the TiO₂ additive improved the hardness of the composites. Corrosion tests in 3.5 wt% NaCl solution showed that the addition of TiO₂/Graphite to copper shifted the corrosion potential in the anodic (more noble) direction, while graphite alone shifted it in the cathodic (less noble) direction. However, graphite-reinforced Cu composites exhibited a better protective oxide film than those TiO₂/Graphite reinforced Cu-based composite, attributed to the uniform distribution of graphite throughout the material. Although TiO₂ or TiO₂/Graphite with graphite improved the corrosion potential, the corrosion current density was higher than that of unreinforced Cu due to the formation of micro-galvanic cells within the composite. Additionally, the high amount of TiO₂ added positively influenced the corrosion resistance. Using graphite's ability to make the composite self-lubricate when used with metals or ceramics, adding graphite to TiO₂ particles at all volume ratios significantly increased the wear resistance of the composite.

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An electroplasticity method for tailoring the flow stress during the thermal deformation of Aermet100 ultra-high strength steel by adjusting the frequency of electropulsing is proposed. This study rigorously controls the electron wind force and Joule heating effect to establish the origin of the electroplastic effect from the perspective of dislocation vibration for the first time. By strictly controlling the electron wind force and Joule heating effect, the origin of the electroplastic effect is verified for the first time from the perspective of dislocation vibration. The results show that the electropulsing frequency of 50 Hz has the lowest flow stress. Moreover, the flow stress of the specimens was nonlinear dependent on the increment in the electropulsing frequency, that it rose first followed by a decline. The electropulsing frequency threshold that can result in the transition in flow stress is 500 Hz. It is attributed to the proximity of the dislocation vibration frequency of Aermet100 steel at high-temperature conditions to the pulsed current frequency, leading to an increase in dislocation amplitude. Furthermore, a pulsed current frequency of 1000 Hz is found to have the highest recrystallization nucleation rate and recrystallized content. It is the threshold for the transformation of grain refinement strengthening. This investigation sheds new insight into the regulation of flow stress and microstructure in Aermet100 ultra-high strength steel using electroplasticity effect.

Double-stage hot deformation tests were implemented to systematically reveal the flow characteristics and microstructure evolution of Ti55511 alloy with fully β phase. The double-stage hot deformation parameters cover wide ranges of strain rates (0.001 s^–1–0.1 s^–1), temperatures (1163–1223 K), first-stage strains (0.3–0.9) and inter-stage holding times (0–120 s). Experimental results show that the reloading yield stress significantly is lower than the yield stress in first-stage (stage-I) deformation. The main softening mechanisms, static recrystallization (SRX) and metadynamic recrystallization (mDRX), contribute to a decrease in the reloading yield stress in the second-stage (stage-II) deformation. When the inter-stage holding time exceeds 60 s, the abnormal grain growth occurs, leading to an increased average grain size. A visco-plastic self-consistent (VPSC) model incorporating double-stage deformation parameters is presented. The model accurately reproduces the microstructure evolution during the double-stage hot deformation. However, its computational efficiency is limited. Therefore, by integrating experimental data with VPSC output, a novel model combining a particle swarm optimization (PSO) algorithm with a long short-term memory (LSTM) network (PSO-LSTM) is introduced to predict flow stress and microstructure evolution. The mean absolute error (MAE), correlation coefficient (R²) and root-mean-square error (RMSE) values between experimental and predicted stresses of the PSO-LSTM model are 0.6252 MPa, 0.9987 and 1.8637 MPa, respectively. Additionally, the proposed PSO-LSTM model can accurately predict the average grain size evolution during the double-stage hot deformation.

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Laser welding with wire filler addition has been a potential manufacture technique for the nuclear pressure vessels manufacturing. However, laser welding by using only single nickel-based alloy wire or austenitic stainless steel wire still faces some challenges, such as non-fusion, cracks, low mechanical properties and C element migration. Thus, we assess the possibility of filling 52 M and 308 l dissimilar wires for a narrow gap laser welding of SA508 and 316 l dissimilar metals in nuclear pressure vessels fabrication in this paper. The results showed that with increasing the ratio of 308 l filling wire from 25 to 75%, the fusion line boundary of 52 M/Weld metal gradually became obvious and the size of the cellular and dendritic grains increased slightly in the weld metal. The results also indicated that the average yield strength (YS) of the welded joints obtained with different ratio of the filling double wires was about 322 MPa, which was between that of the 316 l stainless steel and the SA508 low alloy ferritic steel base metals. Additionally, the average ultimate tensile strength (UTS) of the joints obtained with different ratio of the double filling wires was about 571 MPa, which was lower than that of the 316 l and the SA508 base metal. The maximum UTS of the welded joint was achieved when the 52 M/308L filling wires ratio was 3:1. The maximum impact fracture absorbed energy of the welded joint was obtained when the 52 M/308L filling wires ratio was 1:3. When the ratio of the 308 l filling wire increased, the impact fracture absorbed energy gradually increased.

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective and efficient technology for producing large-scale metallic parts. It is widely adopted in the automotive, aerospace, and marine industries due to its high deposition rate, material efficiency, reduced production time, and lower costs compared to powder-based additive manufacturing techniques. Titanium alloys are extensively used in the aerospace and astronautics industries due to their exceptional mechanical properties and overall performance. However, manufacturing large titanium components using conventional techniques poses significant challenges, particularly when dealing with intricate geometries and a high Buy-To-Fly (BTF) ratio. As a result, WAAM has gained significant traction for its ability to produce near-net-shape, large-scale titanium alloy components with high efficiency, superior quality, and lower production costs. This study first provides an in-depth analysis of WAAM-deposited titanium alloys, highlighting the key challenges associated with the process, including high heat input, oxidation, residual stress distribution, and grain size control. It then explores hybrid WAAM systems and advanced post-processing techniques, including inter-pass cold rolling, inter-pass cooling, shot peening, and ultrasonic impact treatments to mitigate these challenges and enhance material properties. Additionally, the study evaluates the economic feasibility of WAAM for titanium alloys, highlighting its cost advantages over traditional manufacturing methods. Finally, various industrial applications of WAAM-fabricated titanium components are discussed. These findings underscore the critical role of advanced post-processing techniques in overcoming the inherent limitations of WAAM for titanium alloys, paving the way for further improvements in material properties, process efficiency, and industrial adoption.

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Heterostructured (HS) 2024Al alloy composed of Al₃Ti-free coarse grains domains (CGs) and Al₃Ti-reinforced fine grain domains (FGs) was fabricated via powder thixoforming, and its heterogeneity level (the microhardness difference between CGs and FGs) was regulated through T6 heat treatment for further improving tensile properties. The results indicate that for the peak-aged alloy, the numbers of Guinier-Preston-Bagaryatsky (GPB) zone and fine S′′ phase in the FGs are higher than those in the CGs, leading to a moderate heterogeneity level (1.50 GPa), and thus endowing prominent tensile properties (ultimate tensile strength of 539.8 MPa, yield strength of 342.7 MPa, and elongation of 11.14%). Small localized strain regions were formed during deformation, which could efficiently enhance the ability to co-deformation between the CGs and FGs. The improved hetero-deformation induced (HDI) hardening due to the promoted dislocation accumulation at the CGs/FGs interfaces, as well as the mobile dislocations that cut the GPB zones and shearable small-sized S′′ phases, contributed to the excellent ductility. The good strength was mainly ascribed to the HDI strengthening besides precipitation strengthening. This work provides a promising way for optimizing the heterogeneity level and fabrication technology of HS alloys with excellent properties.

Metal three dimensional-printing technology has advanced the fabrication of various metal alloys. One of the most well-known lightweight metal alloys, aluminum alloys, are applied in various fields, including aerospace and automobiles. Aluminum is a special metal with unique chemical and physical properties, including high reactivity to iron that hinders the multi-material additive manufacturing (MMAM) of aluminum and iron-based alloys. The direct deposition of the aluminum alloys onto stainless steel is impossible because the aluminum alloy sides off the base steel. Therefore, a novel anchor design of AISI 316 L stainless steel was developed to prevent this detachment. In this study, laser directed energy deposition (LDED) is proposed for the MMAM of AlSi10Mg and AISI 316 L stainless steel. The hardnesses of the anchor and deposited aluminum alloy were measured. Thereafter, scanning electron microscopy and energy-dispersive X-ray spectroscopy images were observed to determine material solidification and diffusion behavior. Finally, a tensile test was performed to evaluate the bond strength of the aluminum/steel interface. As a result, tensile interface bonding stress of up to 8.4 MPa is produced when the anchor structure was made through rescanning on thin wall with a hatch spacing of the anchor of 1.5 mm. AlSi10Mg was successfully deposited on AISI 316 L stainless steel using LDED. In addition, a macroscopic anchor was designed and manufactured using LDED to overcome the weak bond of the micro-anchor. To demonstrate the Al/Fe MMAM, a multi-material sine wave and QR code were developed.

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The present research aims to estimate the necking and fracture limits of various sheet metals using machine learning (ML) models and to predict the formability of different steel and aluminum sheet metals. Experiments of stretch forming (SF) and single-point incremental forming (SPIF) were performed under uniaxial, plane strain, and biaxial strain paths to estimate failure limits. Further, using different ML algorithms, a supervised ML methodology was proposed to predict the forming limit diagram (FLD) and fracture forming limit diagram (FFLD) of various sheet materials. Subsequently, the ML-predicted FLDs and FFLDs were validated with the experimental data. It was observed that the random forest regressor (RFR), decision tree regressor, and extreme gradient boosting ML models showed high accuracy in prediction, with the RFR model outperforming all other ML models. The accuracy in the prediction of FLD and FFLD for the RFR model was 92% and 96%, respectively. Furthermore, the ML-predicted FLDs and FFLDs were incorporated as failure initiation models into the finite element simulations coupled with the advanced anisotropic Yld2000 material model to perform the post-forming analyses during SF and SPIF processes. It was found that the mean absolute percentage error values in the dome height prediction of all the SF and SPIF samples using the  best-predicted RFR FLD and RFR FFLD were within 10% error values. Moreover, the surface strains and thickness distributions for the SF and the SPIF samples were efficiently predicted using the RFR model-based FLD and FFLD.

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Ultra-high strength steels (UHSS) are widely used in aerospace but are prone to defects such as wear and cracks during service life. Laser cladding offers superior control over heat input and cooling rates, minimizing thermal distortion and promoting a strong metallurgical bond. This study employed AerMet100 steel as the cladding material to repair 30CrMnSiNi2A steel, with a focus on elucidating the microstructural evolution and mechanical property enhancement within the repaired sample. The microstructure primarily consisted of tempered martensite, martensite, lower bainite, and minor retained austenite. Meanwhile, obvious hardness gradient was also observed. The average hardness of the cladding layer, the heat affected zone and the substrate was 500.1 HV, 422.7 HV and 365.6 HV, respectively. The hardness of the repair zone was significantly higher than that of the substrate. This was attributed to solid solution strengthening and M2C carbide precipitation facilitated by the high Co and Ni content in AerMet100. Furthermore, the repair zone exhibited a higher dislocation density, which further contributed to the increased hardness. The strength of the repaired sample reached 1484 MPa, which was improved compared with the matrix performance, indicating that the use of AerMet100 for laser cladding can effectively restore the mechanical properties of 30CrMnSiNi2A steel. This finding provides an effective repair solution for critical aerospace components, particularly landing gear.

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