Pure Alloys Research Articles

Identification and Classification of Aluminum Scrap Grades Based on the Resnet18 Model

In order to reduce the elemental species produced in the recycling and melting of aluminum scrap and to improve the quality of pure aluminum and aluminum alloys, it is necessary to classify the different grades of aluminum scrap before melting. For the problem of classifying different grades of aluminum scrap, most existing studies are conducted using laser-induced breakdown spectroscopy for identification and classification, which requires a clean and flat metal surface and enormous equipment costs. In this study, we propose a new classification and identification method for different grades of aluminum scrap based on the ResNet18 network model, which improves the identification efficiency and reduces the equipment cost. The objects of this research are three grades of aluminum scrap: 1060, 5052, and 6061. The surface features of the three grades were compared using a machine vision algorithm; three different datasets, using RGB, HSV, and LBP, were built for comparison to find the best training dataset for subsequent datasets, and the hyperparameters of learning rate and batch size were tuned for the ResNet18 model. The results show that there was a differentiation threshold between different grades through the comparison of surface features; the ResNet18 network model trained the three datasets, and the results showed that RGB was the best dataset. With hyperparameter optimization of the ResNet18 model, the accuracy of final classification and recognition could reach 100% and effectively achieve the classification of different grades of aluminum scrap.

Unraveling the low thermal conductivity of the LPBF fabricated pure Al, AlSi12, and AlSi10Mg alloys through substrate preheating

It is essential to employ post-build heat treatment on the laser powder bed fusion (LPBF) fabricated aluminum (Al) and Al alloys due to their thermal conductivity in the as-built condition being inferior to that of the conventionally manufactured counterparts. In this study, substrate preheating (200 °C) was proposed as a solution to achieve high thermal conductivities in the as-built condition. Pure Al, AlSi12, and AlSi10Mg samples were shown to possess up to 15 %, 25 %, and 80 % higher thermal conductivity values than their non-preheated counterparts reported in the literature. An analytical analysis contingent on calculating electron mean free path in the presence of only intrinsic or a combination of intrinsic and extrinsic scattering phenomena was introduced to justify the thermal behaviors. As per micro X-ray computed tomography, EBSD analysis, and TEM investigations, the extrinsic scattering sites were found to be (i) pores, (ii) grain boundaries, (iii) cell boundaries (Al alloys), (iv) oxides (pure Al), (v) nano-size Si precipitates (AlSi10Mg), (vi) nano-size Mg 2 Si phase (AlSi10Mg), (vii) vacancies, (viii) dislocations and (ix) Si supersaturation in α-Al phase (Al alloys). The dominant scattering site(s) was found for each material based on which the difference between the obtained thermal conductivity and its corresponding nominal value or the one reported for the non-preheated condition was unraveled. The implications of the findings in this study are essential not only for Al/Al alloys but also for other metallic materials (i.e., Cu alloys), requiring high thermal conductivity in the as-built condition.

MECHANICAL AND TRIBOLOGICAL CHARACTERIZATION OF HYBRID Al6061/B4C/Gr COMPOSITES BY STIR CASTING TECHNIQUE

This research focuses on the fabrication of Al6061/B4C/Gr metal matrix composites as well as the mechanical and wear properties analysis. A liquid metallurgy stir casting process was used to cast the Al6061 alloy matrix composites with specific wt.% of B4C and constant wt.% of graphite. In this work, newly developed composites of Gr (particle grain size: 0–20[Formula: see text][Formula: see text]m) and B4C (particle grain size: 0–30[Formula: see text][Formula: see text]m) are reinforced with Al6061 pure alloy, which enhanced the mechanical and wear properties when compared to Al6061 pure alloy. Microstructure analysis was carried out concerning the developed mechanical properties. Furthermore, the dry sliding wear behavior of Al6061/B4C/Gr metal matrix composites was investigated at a sliding speed of 1[Formula: see text]m/s and a sliding distance of 1500[Formula: see text]mm against a hardened EN-31 disc under the corresponding load of 19.68[Formula: see text]N. The minimum wear rate is [Formula: see text][Formula: see text]mm3/m found at 15[Formula: see text]wt.% B4C and 2[Formula: see text]wt.% graphite and the coefficient of friction is 0.54 that decreases with graphite addition, with the lowest value obtained with 5[Formula: see text]wt.% B4C and 2[Formula: see text]wt.% graphite. Al6061/10[Formula: see text]wt.% B4C/2[Formula: see text]wt.% Gr particles-reinforced composite material demonstrated the highest tensile and flexural strengths. The hardness,compressive and tensile strength of the Al6061/15[Formula: see text]wt.% B4C/2[Formula: see text]wt.% Gr particles-reinforced composite material were the highest. Scanning electron microscopy was used to examine the worn surfaces of wear specimens. The main objective of this work is to develop hybrid Al6061/B4C/Gr composites with improved mechanical and wear properties when compared with the base alloy. Al6061 is widely used in automobiles parts like engine block, piston rings, alloy wheels, marine industries, etc. B4C used in the composite improves strength and is used commonly in armed bullet proof. The Gr present in the composite improves wear resistance, and therefore applied in wear-resistant parts like brake, piston with cylinder, etc.

Plasma electrolytic oxidation of as-cast and heat-treated binary Al-Ni alloys

In this study, the effect of nickel addition on the plasma electrolytic oxidation (PEO) behavior of pure Al was investigated. Binary Al-Ni alloys containing 1, 3, 5 and 7 at. % Ni were produced by two step vacuum arc and induction melting methods. Produced alloys and pure Al as a reference were PEO coated in a silicate-based alkaline electrolyte through a bipolar power source under constant voltage mode for 45 min. The samples were characterized by XRD, SEM-EDS and Vickers microhardness tester before and after PEO. All alloys were consisted of Al and Al3Ni phases. Fine rod-like eutectic structure was evident for 1 (hypoeutectic) and 3 (eutectic) at. % Ni containing alloys while further addition of Ni resulted in the coarsening of eutectic Al3Ni precipitates. All coatings contained γ-Al2O3 phase while additionally, α-Al2O3 phase formed on pure Al and Al-1Ni alloy. Despite the presence of Ni in the coatings, a Ni-based oxide phase was not evident. Ni, as an alloying element, is found to decrease microhardness and thickness of the coatings, induced a thickness variation between the regions close to the edge and center of the samples. This edge effect was maximum on eutectic alloy, which consisted of homogeneously distributed fine Al3Ni precipitates. To investigate the relationship between eutectic precipitate size and the edge effect, Al-3Ni alloy was heat-treated at 620 °C for 168 h and subsequently coated by PEO. Heat-treatment almost eliminated the edge effect, increased the average coating thickness and promoted the α-Al2O3 formation. Fine eutectic morphology in Al-Ni alloys is found to be detrimental for the coatings produced by PEO.

Effect of Vanadium on the Microstructure, Transformation Temperatures, and Corrosion Behavior of NiTi Shape Memory Alloys

Abstract Ni50Ti50-xVx (x = 0, 1, 2, 3 at%) shape memory alloys were prepared by vacuum induction melting. They were homogenized and then hot rolled. Carbon hydrogen nitrogen oxygen sulfur (CHNOS) and X-ray diffraction (XRD) analyses were carried out on the alloys to find out the oxygen and carbon contents and the phases present in the alloys. Transformation temperatures determined by differential scanning calorimetry indicate that the addition of vanadium reduces the transformation temperatures. Corrosion studies were carried out in Hanks’ solution, while potentiodynamic polarization tests were done to calculate the rate of corrosion of the alloys. Two significant parameters were analyzed from the Tafel graph, namely, corrosion rate and corrosion potential. A comparison of these properties of the alloys was also made with commercially pure titanium and binary NiTi alloys. Among the NiTiV alloys, Ni50Ti47V3 (at%) alloy was found to undergo the least rate of corrosion. With the increasing vanadium content, the rate of corrosion was found to decrease. Scanning electron microscopy (SEM) analysis of the corroded surface shows that pitting was the main mechanism of corrosion in these alloys. Results show that the addition of V to NiTi has a positive effect on the corrosion properties of the alloys. Elaborate results are discussed in detail in this article.

Construction and osteogenic effects of 3D-printed porous titanium alloy loaded with VEGF/BMP-2 shell-core microspheres in a sustained-release system.

The repair and reconstruction of bone defects remain a challenge in orthopedics. The present study offers a solution to this problem by developing a vascular endothelial growth factor (VEGF)/bone morphogenetic protein 2 (BMP-2) shell-core microspheres loaded on 3D-printed porous titanium alloy via gelatin coating to prepare a titanium-alloy microsphere scaffold release system. The composite scaffold was characterized via scanning electron microscope (SEM) and energy disperse spectroscopy (EDS), and the effect of the composite scaffold on the adhesion, proliferation, and differentiation of osteoblasts were determined in vitro. Furthermore, a rabbit femoral defect model was established to verify the effect of the composite scaffold on osteogenesis and bone formation in vivo. The results demonstrated that the composite scaffold could release VEGF and BMP-2 sequentially. Meanwhile, the composite scaffold significantly promoted osteoblast adhesion, proliferation, and differentiation (p < 0.05) compared to pure titanium alloy scaffolds in vitro. Furthermore, the composite scaffold can exhibit significant osteogenic differentiation (p < 0.05) than gelatin-coated titanium alloy scaffolds. The in vivo X-rays demonstrated that the implanted scaffolds were in a good position, without inflammation and infection. Micro-CT and quantitative results of new bone growth illustrated that the amount of new bone in the composite scaffold is significantly higher than that of the gelatin-coated and pure titanium alloy scaffolds (p < 0.05). Similarly, the fluorescence labeling and V-G staining of hard tissue sections indicated that the bone integration capacity of the composite scaffold was significantly higher than the other two groups (p < 0.05). This research suggests that VEGF/BMP-2 shell-core microspheres loaded on 3D-printed titanium alloy porous scaffold through gelatin hydrogel coating achieved the sequential release of VEGF and BMP-2. Most importantly, the in vitro and in vivo study findings have proven that the system could effectively promote osteogenic differentiation and osseointegration.

Co-deposited CuNi@MWCNTs nanocomposites for structural applications: tribo-mechanical and anti-corrosion performances

ABSTRACT In the present work, multi-walled carbon nanotube (MWCNT) nanofiller reinforced copper-nickel alloy (CuNi@MWCNTs) nanocomposites were synthesised by a modified electro-chemical co-deposition followed by compaction and sintering. During this method, CuNi@MWCNTs were co-deposited on a cathode tip at room temperature and collected from the electro-chemical bath in powdered form. Subsequently, the powdered nanocomposites were dried, compacted and sintered to prepare solid pellets. The influence of different amounts (25, 50 and 100 mg L−1) of MWCNT nanofillers in the deposition bath on microstructure, mechanical and anti-corrosion properties of CuNi@MWCNTs nanocomposites was investigated. The microhardness, compressive yield strength and friction coefficient of CuNi@MWCNTs (100 mg L−1) nanocomposites were enhanced by 45.7%, 37.2% and 55.1%, respectively, compared to that of pure CuNi alloy. In addition, the CuNi@MWCNTs nanocomposites obtained also exhibited improved anti-corrosion property in 3.5 wt.% NaCl solution at continuous agitation of 150 rpm and 27°C temperature. Based on the research outcomes, this approach for synthesising CuNi@MWCNTs nanocomposites may be proposed for scale-up industrial trials.

AlCo-rich AlCoNiFe and AlCoNiFeCr high entropy alloys: Synthesis and interaction pathway at high heating rates

Novel AlCo-rich AlCoNiFe and AlCoNiFeCr high entropy alloys (HEAs) were prepared from the non-activated and mechanically activated (MA) quaternary Al40Co40Ni10Fe10at% and quinary Al35Co35Ni10Fe10Cr10at% mixtures. The wide temperature range of the formation of a single high entropy alloy of BCC structure in quaternary system and the formation of pure quinary AlCoNiFeCr alloy above 740 °C was predicted by thermodynamic modelling. The underlying interaction mechanism was proposed, and the effective activation energy values were deduced at high heating rates up to 2600 °C·min−1 by thermal analysis method through high-speed temperature scanner. The presence of a single-stage exothermic interaction in the non-activated and mechanically activated quaternary and quinary mixtures was attributed to HEA formation via either solid + liquid or solid + solid mechanism depending on the heating rate and mechanoactivation (MA) duration. The influence of heating rate and MA duration on the self-heating profile and reaction onset temperature was also deduced. Microstructure evolution and phase formation sequence were monitored by the examination of products quenched at characteristic temperatures at synthesis and processing of AlCo-rich AlCoNiFe and AlCoNiFeCr HEAs. The crystallite size (CS), lattice strain (LS) and lattice parameter (LP) of CoFeNiAl and CoFeNiAlCr HEAs were estimated according to MA duration. The thermal stability in argon and air flow conditions at heating rate of 40 °C·min−1 for up to 1200 °C was studied by thermogravimetric analyser complemented with X-ray diffraction analysis.

Simultaneous analysis of long-pulse laser irradiated plasma-facing materials (PFMs) microstructure and hardness by in-situ laser Opto-ultrasonic dual detection (LOUD)

Laser-induced transient heat load events such as edge localized mode (ELM) could induce recrystallization, grain growth, surface degradation, and hardness changes. In this regard, we used the long-pulse laser beams with power densities ranging from 0.165 to 1.909 GW m−2 to simulate transient heat load events for pure tungsten and tungsten heavy alloy (WHA) materials. The investigated samples showed that pure tungsten exhibited a higher recrystallization threshold, steady grain growth, and less surface hardness deterioration than WHA. However, the real-time simultaneous analysis of structural and mechanical properties such as matrix elements, grain size, surface degradation, and hardness changes is challenging in this domain. Therefore, in this study, we utilized a novel laser Opto-ultrasonic dual detection (LOUD) multimodal technique that integrates the benefits of laser-induced breakdown spectroscopy (LIBS) and laser ultrasonic testing (LUT) for simultaneous and in-situ detection of elemental information, grain size and hardness. The preliminary results showed that the variation in hardness is well correlated with the LIBS calibration curve formed by the ionic to atomic line intensity ratio and plasma electron temperature (Te). Despite the different matrix compositions of both samples, the observed increase in the value of Te with hardness justifies the Saha-Eggert relation. The coefficient of determination (R2 ≥ 0.970) value in the calibration curve and Te for hardness evaluation showed the goodness of the fitted model. Furthermore, the correlation of grain size with ultrasonic acoustic attenuation (α) was analyzed by the pulse-echo technique of the ultrasonic waveform for investigated samples. The results showed that grain size is also directly associated with acoustic attenuation with R2 > 0.989. The findings showed that the regression coefficient has a good approximation, which demonstrates the preciseness and potential ability of the LOUD technique for in-situ grain size and hardness analysis.

An Application Based Introduction to the Brush Plating Technique

Selective or brush plating is an application method for electrodeposition which can be used for depositing an array of pure metals, alloys, and composite materials onto conductive surfaces. Brush plating has seen its most advantageous use in plating smaller areas of larger parts because the amount of masking used can be reduced, and smaller volumes of solution can be utilized compared to traditional tank plating methods. These same characteristics make brush plating portable and repair operations can be conducted in the field, at times without even disassembling equipment. Brush plating is currently used across a multitude of industrial applications in the fields of aerospace, oil and gas, marine environments, semiconductors, and other manufacturing.‘Brush’ plating is often considered a manual technique where a technician directly applies the anode (wrapped in the ‘brush’ material) to the surface to be plated. The brush material must be a porous, non-conductive, flexible material which electrically separates the anode from the surface to be plated. The plating solution is absorbed into the brush material around the anode prior to plating by dipping it into a vessel containing the solution. Alternatively, solution can be pumped directly through the anode to the surface to be plated. As a result, smaller volumes of solution can be used because the entire part is not immersed in a large tank containing the plating solution. Masking can be placed around the area to be plated without needing to mask off every surface that isn’t receiving a deposit.The current density used for brush plating is often high (0.2 to 1.5 A/cm2) relative to other electrochemical plating techniques. Brush plating solutions are typically highly concentrated and the brushing action against the surface where deposition is occurring allows for replenishment of the ion to be plated very close to the interface with the cathode. This allows for high plating rates (Up to 500 µm/hr) depending on the solution and other plating parameters utilized.This presentation will introduce the audience to the brush plating technique through the use of current and classical applications with multiple deposits. Pros and cons of the technique for different circumstances will be discussed. The influence of the brush material on the electrochemical interface during plating and the resulting deposit will be highlighted. Current research includes the development of deposits for chrome alternatives, alloys for corrosion resistance, and applying deposits to challenging substrates.

(Digital Presentation) Spark Plasma Sintering Fabrication of α/β Interface in Mg Alloys and Analysis of Corrosion Behavior

In Mg alloys, corrosion behavior is known to be related to the microstructure. For example, AZ91D alloy contains an α matrix phase (Mg solid solution), β phases (Mg17Al12) and lamellar α+β microstructures. During the real-time in situ observation of the corrosion process under galvanostatic polarization, filiform corrosion proceeded along the outside of the β-phase (in lamellar α + β microstructure and along the α-mother phase[1]. However, the detailed mechanism of the initiation and growth of filiform corrosion is still unknown. An electrode area contains simplified α + β structure is needed to clarify the corrosion mechanism of Mg alloys. The fabrication of such specimen could be actualized by Spark Plasma Sintering (SPS).The advantage of SPS is that it can produce specimens with high efficiency and few pores. The energy from the pulsed current, self-heating of the workpiece, and particle-to-particle discharge are the combined driving force for sintering. In recent years, many experiments have been reported on the fabrication and strength evaluation of pure Mg and Mg alloys. However, only a few studies have been conducted on the fabrication and corrosion resistance of different phases.In this study, we attempted to fabricate the interface of β and α phases by SPS using pure Al powder and pure Mg powder and other materials. The characterization of different phases was carried out by XRD, EPMA and TEM. The corrosion behavior of the sintered specimens was then observed using an in-situ observation system during open circuit potential measurements. After measurements, the specimen surface was assessed using OM, AES, and FE-SEM.When a 0.25 mm thick Mg sheet was surrounded by pure Al powder, the temperature was set at 420 °C and kept for 30 minutes, a uniform white microstructure was found to form around the Mg sheet. The thickness is about 50 µm. EDS maps and point analysis show that this phase consists a β-phase (Mg17Al12) on the Mg sheet side and Mg23Al30 on the Al powder side. The thickness of the β-phase did not change obviously when the sintering time was extended to 1 hour. Finally, a β phase with a thickness of about 100 μm could be fabricated by using a specimen assembly method of outer Al powder, intermediate layer Mg powder. Analysis of corrosion behavior was done with this specimen. Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Corrosion Science, 192, 109834 (2021).

Effectiveness of photofunctionalized titanium alloy on osseointegration in rats with type 2 diabetes

BackgroundUltraviolet (UV) light-mediated photofunctionalization improves the osseointegration of pure titanium and titanium alloy (Ti6Al4V). However, little is known about the effect of UV irradiation on Ti6Al4V, used frequently in orthopedic surgery, in diabetic patients. We examined the effect of UV irradiation on Ti6Al4V in rats with type 2 diabetes.MethodsCylinder Ti6Al4V implants were used. Half the animals were Sprague Dawley rats (the control group), and the other half were Spontaneously Diabetic Torii fatty rats (the diabetes mellitus model). For radiological analysis, bone density was observed and calculated using 3D microcomputed tomography. Histological analysis was performed to calculate the bone–implant contact (BIC) ratio. We used Pearson correlation to analyze the correlation between average blood glucose level and BIC ratio, and between average blood glucose level and bone volume (BV) ratio.ResultsIn the UV light-treated group, the BIC ratios of the normal and diabetic rats increased significantly compared with those in the untreated group at 2 weeks; at 4 weeks, the BIC ratio of the diabetic rats increased significantly, but there was no significant increase in the control animals. In both the control and diabetic groups, there was no significant difference in the BV ratios between the UV-treated and untreated implants at 2 or 4 weeks. The average blood glucose level in the 4-week group negatively correlated with the BIC and BV ratios. The average blood glucose level in the UV-treated group negatively correlated with the BIC ratio.ConclusionPhotofunctionalization of Ti6Al4V implants may promote osseointegration in the early stages in rats with type 2 diabetes.

An efficient temperature-dependent crystal plasticity framework for pure magnesium with emphasis on the competition between slip and twinning

Experimental evidence suggests that the formation of compressive twin bands and the associated strain localization is a key driver behind the low ductility of magnesium (Mg) at ambient temperature, which is why processing is often performed at elevated temperature. Modeling Mg and its alloys across the temperature range of interest is challenging and must account for the experimentally reported competition between compressive twins and pyramidal slip. Unfortunately, only few temperature-aware models for pure Mg and Mg alloys exist and many either disregard compressive twins entirely or suffer from efficiency or calibration issues, while experimental evidence of the active deformation modes has remained inconclusive. To describe the temperature-dependent behavior we introduce a new efficient, temperature-aware crystal-plasticity framework for pure Mg. Experimental stress–strain and texture data are used to calibrate the model over the range from room temperature to 300 °C. The calibrated model predicts single- and polycrystal stress–strain responses accurately in comparison with experimental data. By comparing two versions of the model – with and without compressive twins – we highlight their impact on the microstructure and texture evolution. Results highlight a transition in deformation modes from compressive twins at low temperature to pyramidal II slip at elevated temperature, confirming that the temperature dependence of pure Mg is primarily governed by non-basal slip. We thus provide an accurate and efficient modeling tool for the temperature-dependent mechanical behavior of pure Mg, while also shedding light onto the relative importance of non-basal slip vs. compressive twins as a function of temperature.

Microstructure and mechanical properties of additive manufactured Inconel 718 alloy strengthened by oxide dispersion with 0.3 wt% Sc addition

Additively manufactured superalloys have attracted increasing attention due to their inherent hierarchical microstructure, but have been impeded by anisotropic properties originating from columnar grains. In this work, we present a strategy for inhibiting the formation of columnar grains in which 0.3 wt% scandium (Sc) was introduced as an oxide dispersion strengthener (ODS) into the Inconel 718 (IN718) alloy fabricated via laser powder bed fusion (LPBF). The effects of Sc on the microstructure and mechanical properties of the IN718 were investigated, revealing the in-situ formation of Sc 2 O 3 nanoparticles as well as the cellular sub-grains microstructure with high-density of dislocations into the as-prepared IN718-Sc alloy. The addition of Sc disrupted the typical columnar grains generated by the LPBF process, resulting in, the strong (100) texture in pure IN718 alloy changing to the irregular orientation in IN718-Sc alloy. In addition, the average grain size and the aspect ratio also show decreases when Sc introduction. As a result, the as-designed IN718-Sc alloy achieved a higher yield strength of 1030 MPa at room temperature and 837 MPa at 650 ºC, respectively, which can be attributed to Zener pinning of grain boundaries by dispersed Sc 2 O 3 nanoparticles. Importantly, the insight into dispersing oxide particles to regulate microstructure and improve properties in this study could provide guidance for other alloy fabrication through powder additive manufacturing. • Generating in situ rare earth oxides as nucleating agent, the columnar grains trend was suppressed. • With Sc addition, the grain size was refined and Sc 2 O 3 was generated to pin dislocation. • IN718-Sc exhibited a 20% increase in yield strength at room temperature and high temperature.

Corrosion behavior of severely plastically deformed Mg and Mg alloys

Magnesium (Mg) alloys have several advantages, such as low density, high specific strength and biocompatibility. However, they also suffer weak points, such as high corrosion, low formability and easy ignition, which makes their applications limited. Many studies have been conducted to overcome these disadvantages and further improve the advantages of Mg alloys. Severe plastic deformation (SPD) is one of the most important techniques and has great effects on the microstructure refinement of Mg alloys and improvements in their strength and formability. Several researchers have studied the corrosion behavior of SPD-processed Mg alloys in recent decades. However, these studies have reported some controversial effects of SPD on the corrosion of Mg alloys, which makes the research roadmap ambiguous. Therefore, it is important to review the literature related to the corrosion properties of Mg alloys prepared by SPD and understand the mechanisms controlling their corrosion behavior. Effective grain refinement by SPD improves the corrosion properties of pure Mg and Mg alloys, but control of the processing conditions is a key factor for achieving this goal because texture, dislocation density, size and morphology of secondary phase also importantly affects the corrosion properties of Mg alloys. Reduced grain size in the fine grain-size range can decrease the corrosion rate due to the increased barrier effect of grain boundaries against corrosion and the formation of a stable passivation layer on the surface of fine grains. Basal texture reduces the corrosion rate because basal planes with the highest atomic planar density are more corrosion resistant than other planes. Increased dislocation density after SPD deteriorates the corrosion resistance of the interior grains and thus proper annealing after SPD is important. The fine and uniform distribution of secondary phase particles during SPD is important to minimize the micro-galvanic corrosion effect and retain small grains during annealing treatment for removing dislocations.

Grain refinement of Mg-Al binary alloys inoculated by in-situ oxidation

Utilizing oxide inclusion to induce heterogeneous nucleation event is an available method to achieve grain refinement. In this study, Mg-Al binary alloys were refined by inoculation of in-situ oxidation process. Results show that MgO and MgAl2O4 phases are primary oxide products for Mg-xAl alloys inoculated by in-situ oxidation. For pure Mg and Mg-1Al alloy, MgO is the only oxide product. MgAl2O4 is another oxide product for Mg-xAl alloy as Al content increases to 3 wt.%. For Mg-3Al alloy, average grain size significantly decreases from 1135 to 237 μm, with a high grain refining ratio of 79.1%. Both MgO and MgAl2O4 possess nucleating potency for α-Mg grain. MgAl2O4 exhibits a higher nucleating potency due to the lower misfit with α-Mg. The grain refinement of Mg-xAl alloys inoculated by in-situ oxidation process is attributed to heterogeneous nucleation events of α-Mg grains on MgO or MgAl2O4 particles.

Pronounced inhibitory mechanism of Cr on vacancy-like defects in Fe9Cr alloy irradiation with helium ions

• First-principles calculations combined with positron annihilation spectroscopy. • The He atoms aggregate among (1 1 0) planes in the perfect Fe and Fe9Cr models. • Fe atoms around the He clusters are inclined to emit spontaneously. • The doping of Cr repels the He atoms and weakens the growth of He clusters. First-principles calculations and positron annihilation spectroscopy were used to investigate the effect of Cr atoms on He-induced vacancy-like defects in pure Fe and Fe9Cr alloys. The He atom is not energetically favorable at both the surface and the subsurface, but it becomes stable under the third atomic layer from the surface. The diffusion of He atoms to the vacuum and aggregation of He atoms into clusters coexist. We observed that the interstitial He n clusters prefer to stay along the (1 1 0) plane. Moreover, the small He n clusters induce strong lattice distortions, and the emission of a self-interstitial Fe atom located at the adjacent He n cluster is energetically favorable for n > 2 and vacancy formation energies of Fe9Cr are higher than that of Fe. This suggests that Cr atoms could effectively enhance the stability of Fe atoms around He n clusters but that the Fe atoms would still like to shift from the vicinity of He n to the surfaces of the models. In the experiment, Fe and Fe9Cr alloys were irradiated with He ions to a dose of 1 × 10 16 cm 2 and the positron annihilation results showed that the Fe9Cr alloy has a smaller relative S (ΔS) parameter value than pure Fe. The experimental results matched well with the theoretical analysis. These results would help provide additional insights into the behavior of He in irradiated Fe and Fe9Cr surfaces, necessary for the interpretation of the growth of the He bubble.

Relationship between the Composition and Elastic Modulus of TiZrTa Alloys for Implant Materials

The elastic modulus is a key factor influencing the applications of implant materials because of the weakening effect of stress shielding. Ti and its alloys are good potential implant materials thanks to their low elastic modulus and fine biocompatibility. The addition of alloying elements into pure Ti and Ti alloys is the basic way to further decrease the elastic modulus whilst simultaneously enhancing strength, wearability, and corrosion resistance, for example. Finding the relationship between the composition and elastic modulus can greatly promote the development of Ti alloys with a low modulus for implant applications. In the current work, we investigated the elastic modulus of TiZrTa alloys with scores of compositions by using the high-throughput diffusion couple method, nanoindentation, and an electron probe micro-analysis. The relationship between the elastic modulus and the composition of the TiZrTa alloys was obtained. The average valence electron theory was employed to make clear the variation between the elastic modulus and the composition. Finally, the composition range formulae of TiZrTa alloys likely to have a low modulus were established by combining our data and previous results. These findings are helpful in developing new Ti alloys with a low modulus and also help to further understand the alloying theory.

Impact Joining of Pure Copper C1100 and Aluminum Alloy A6061-T6 Plates at Edges

Joining of pure copper C1100 and aluminum alloy A6061-T6 plates of 5 mm thickness was investigated. The method was developed by one of the authors, in which the newly created surfaces of a pair of plates obtained by high-speed shear were immediately in contact with a sliding motion with a small overlap length. The total processing time was just about a few milliseconds. To create the new surface, high-speed shaving was also tested. The joining was not possible for the full thickness of the plates. A sharp notch was observed at the joint boundary due to a large shear droop in the copper. Shaving decreased the shear droop, and the joint length through the plate thickness became longer. The joining performance was evaluated by a uniaxial tensile test. The joint efficiency reached 100% using the specimen cut out from the really joined boundary. The affected zone of joining was confirmed by the hardness distribution near the boundary. It was about 30% of the thickness of the plate, which was much smaller than that in welding by heat, and no softened zone was found in both materials.

Interpretable Machine Learning Analysis of Stress Concentration in Magnesium: An Insight beyond the Black Box of Predictive Modeling

In the present work, machine learning (ML) was employed to build a model, and through it, the microstructural features (parameters) affecting the stress concentration (SC) during plastic deformation of magnesium (Mg)-based materials are determined. As a descriptor for the SC, the kernel average misorientation (KAM) was used, and starting from the microstructural features of pure Mg and AZ31 Mg alloy, as recorded using electron backscattered diffraction (EBSD), the ML model was trained and constructed using various types of ML algorithms, including Logistic Regression (LR), Decision Trees (DT), Random Forest (RF), Naive Bayes Classifier (NBC), K-Nearest Neighbor (KNN), Multilayer Perceptron (MLP), and Extremely Randomized Trees (ERT). The results show that the accuracy of the ERT-based model was higher compared to other models, and accordingly, the nine most-important features in the ERT-based model, those with a Gini impurity higher than 0.025, were extracted. The feature importance showed that the grain size is the most effective microstructural parameter for controlling the SC in Mg-based materials, and according to the relative Accumulated Local Effects (ALE) plot, calculated to show the relationship between KAM and grain size, it was found that SC occurs with a lower probability in the fine range of grain size. All findings from the ML-based model built in the present work were experimentally confirmed through EBSD observations.