Search Results (186)

In this study, dry sliding wear tests were carried out on Er, Zr-microalloyed Al-Zn-Mg alloys with different Zn/Mg ratios under 30–70 N loads. The effects of the Zn/Mg content ratio and Er microalloying on the friction coefficient, wear volume loss, worn surface, and wear debris during the friction process of Al-Zn-Mg alloys were analyzed. At the load of 30 N, abrasive wear, fatigue wear, and adhesive wear were synergistically involved. At a load of 50 N, the abrasive wear dominated, accompanied by fatigue wear and adhesive wear. At a load of 70 N, the primary wear mechanisms transitioned to abrasive wear and fatigue wear, with additional adhesive wear and oxidative wear observed. Reducing the Zn/Mg ratio mitigated wear volume across all tested loads. For the Al4.5Zn1.5Mg alloy, Er microalloying significantly reduced wear volume under moderate-to-low loads (30 N, 50 N). Full article

A method for generally predicting interface chemical bonding at the metal–oxide interface with the interface reaction considered is reported. So far, the interface between pure metal or alloy and 11 oxides—MgO, Al₂O₃, SiO₂, Cr₂O₃, ZnO, Ga₂O₃, Y₂O₃, ZrO₂, CdO, La₂O₃, and HfO₂—without considering the interface reaction, has been discussed and implemented in the free web-based software product InterChemBond (v2022). Now, the number of oxides available for prediction is 83 in total. Among them, 29 oxides are in one stable valence, and the others are multi-valence. The newly developed prediction method considering the interface reaction is additionally implemented in InterChemBond. The principles and formula for predicting interface bonding while considering interface reactions are provided as well as some screenshots of the software. Full article

A hot compression simulation was conducted on the Al-7.62Zn-2.22Mg-0.90Cu-0.30Mn-0.09Er-0.13Zr alloy (7E97) within the temperature range of 300~460 °C and strain rate range of 0.001~10 s⁻¹ using a Gleeble-3500 hot simulator. A flow-stress constitutive equation and hot processing maps were established for the alloy, and the microstructural evolution of the alloy after hot deformation was investigated. It was found that the dominant dynamic softening mechanism of the alloy was dynamic recovery, accompanied by minor dynamic recrystallization. The optimal hot processing window for the alloy was determined to be in the ranges of 0.001~0.05 s⁻¹ and 350~410 °C. Full article

One of the most effective methods of improving the properties of aluminium alloys is grain refining using Al-Ti-B master alloys. In contrast, zirconium is a key alloying element, used mainly in 2xxx and 7xxx series aluminium alloys, where it contributes to dispersion enhancement and reduces the rate of dynamic recrystallisation. However, even trace amounts of zirconium—just a few hundredths of ppm—significantly reduce the performance of Al-Ti-B grain refiners, a phenomenon known as ‘Zr poisoning’. This study investigates the impact of holding time and the level of Al-5Ti-1B addition on the microstructure and properties of an AlMgSi(Cu) alloy containing 0.15 wt.% Zr, cast as 7-inch DC billets. The structure and phase distribution were characterised using optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Grain size and morphology were evaluated through macrostructure analysis (etched cross-sections and polarised light microscopy), while chemical and elemental distributions were analysed via SEM-EDS and STEM-EDS mapping. Additionally, Brinell hardness measurements were conducted across the billet diameter to assess the correlation between grain size and mechanical properties. The results show that reducing holding time and increasing the Al-5Ti-1B addition improves grain refinement efficiency despite the presence of Zr. The finest grain structure (150–170 μm) and most homogeneous hardness distribution were achieved when the grain refiner was continuously fed during casting at 80 ppm B. These findings are supported by the literature and contribute to a deeper understanding of the Zr poisoning effect and its mitigation through optimized casting practice. Full article

The mechanical properties of materials are fundamentally determined by the behavior of atomic bonds under stress. Probing bond behavior during deformation, however, is highly challenging, particularly for materials with complex chemical compositions and/or atomic structures, such as metallic glasses (MGs). As a result, a significant gap exists in the current understanding of the mechanical properties of MGs in relation to the atomic bond behavior and how this relationship is influenced by metallurgical factors (e.g., alloy composition, processing conditions). Here, we present our study of the compositional effects on the tensile behavior of atomic bonds in Cu_93−xZr_xAl₇ (x = 40, 50, 60 at.%) MGs using large-scale molecular dynamics (MD) simulations and statistical analysis. Specifically, we examine the populations (fractions), mean bond lengths, mean bond z-lengths, and mean bond z-strains of the different bond types before and during tensile loading (in the z-direction), and we compare these quantities across the different alloy compositions. Among our key findings, we show that increasing the Zr content in the alloy composition leads to shortened Zr-Zr, Al-Cu, Al-Zr, and Cu-Zr bonds and elongated Cu-Cu bonds, as evidenced by their mean bond lengths. During deformation, the shorter Zr-Zr bonds and longer Cu-Cu bonds in the higher-Zr-content alloys, compared with those in the x = 40 alloy, appear stronger (more elastic stretching in the z-direction) and weaker (less z-stretching), respectively, consistent with general expectations. In contrast, the Al-Cu, Al-Zr, and Cu-Zr bonds in the higher-Zr-content alloys appear weaker in the elastic regime, despite their shortened mean bond lengths. This apparent paradox can be reconciled by considering the fractions of these bonds associated with icosahedral clusters, which are known to be more resistant to deformation than the rest of the glassy structure. We also discuss how the compositional effects on the bond behavior relate to variations in the overall stress–strain behavior of the different alloys. Full article

The microstructure evolution and corrosion behavior of T6-treated Al–Si–Mg alloys were investigated in the presence of Zr and Y additions by using X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM), electrochemical measurement, and X-ray photoelectron spectroscopy (XPS). The results show that the coarse dendritic α-Al was refined into finer, equiaxed grains by adding 0.2 wt% Zr, which further promoted the formation of a uniform and dense passive layer in 3.5% NaCl solution at room temperature (≈25 °C). In contrast, the Al–Si–Mg alloy containing 0.3 wt% Y exhibited the highest corrosion rate. This phenomenon arises from converting rod-like eutectic Si particles into a spherical morphology, which exacerbates the intergranular corrosion network and enhances galvanic coupling effects. Full article

This article evaluates the possibility of replacing creep-resistant magnesium Mg-Zn-RE-Zr alloys (EZ33) with Mg-Al-Ca-Sr alloys. (1) Background: Mg alloys with RE metals show excellent properties. Due to their high cost, new, more economical Mg alloys are being developed. Replacing RE metals with cheaper elements such as Al and Ca allows us to obtain high mechanical properties at elevated temperatures due to the tendency to form stable intermetallic phases. (2) Methods: Microstructure analysis (LM, SEM, TEM, and XRD) was performed and mechanical properties were tested at ambient and elevated temperatures. (3) Results: Increasing the Ca content and decreasing the Al content leads to the formation of a continuous skeleton of high-melting and brittle Ca-rich Laves phases and Sr-rich intermetallic phases and the formation of plate-like precipitates of the C15 phase inside the α-Mg solid solution. The crystallographic orientation of plate-like precipitates contributes to the blocking of dislocations in slip systems activated at elevated temperatures. Increasing the Ca and Sr content allows for the regulation of the Al concentration in the α-Mg, providing solution strengthening and stability of the α-Mg solid solution. These factors contribute to a significant improvement in creep resistance of Mg-Al-Ca-Sr alloys. (4) Conclusions: The strength properties and elongation at ambient temperature of the Mg alloys with Ca and Sr addition are comparable to those of the EZ33 alloy, and due to the presence of lighter alloying elements, a better specific strength is achieved. Ca-rich Mg-Al-Ca-Sr alloys exhibit better creep resistance at temperatures of up to 200 °C compared to the EZ33 alloy. Full article

The Er-Zr-Sc-modified Al-Mg alloys produced by additive manufacturing (AM) exhibit good formability and excellent mechanical properties, and present great potential for applications in the fields of aerospace and automotive fields. In this work, the preparation process of Al-4.5Mg-0.7Er-0.5Zr-0.3Sc high-strength aluminum alloy powder for additive manufacturing by vacuum induction melting gas atomization (VIGA) was investigated. With the goal of obtaining excellent sphericity and higher powder yield in the particle size range of 15~53 μm, a new type atomizer with optimized convergence angle and tube extension length was designed based on finite element numerical simulation and experimental research, and the optimal atomization processing parameters were determined. The results revealed that when the convergence angle was 32° and the extension length was 5 mm, the large negative pressure and suction force at the tube outlet could facilitate the smooth flow of the melt and a refined powder particle size; when the melt temperature was 800 °C and the atomization pressure was 3.25 Mpa, the melt had low viscosity and the atomization gas could fully interact with the melt. Meanwhile, the melt droplets had suitable cooling conditions, avoiding the generation of irregular powders and improving the powder sphericity. Under the above optimal processing parameters, the prepared powders were spherical or nearly spherical with fine particle size and a high yield of about 39.45%. Full article

The influence of annealing temperature on the mechanical properties, microstructural evolution, and recrystallization behavior of AA5083 cold-rolled sheets with and without Sc/Zr microalloying was studied utilizing hardness tests, optical microscopy, electron backscatter diffraction, and transmission electron microscopy. The results show that a minor addition of Sc/Zr to the Al-Mg-Mn alloy can significantly improve the alloy strength and recrystallization resistance. Adding 0.1 wt.% Sc and 0.08 wt.% Zr raised the recrystallization temperature of heavily deformed sheets to 500 °C, which is 250 °C higher than for the Sc-free base alloy. The higher recrystallization resistance of the Sc-bearing alloy was mainly attributed to the presence of Al₃(Sc,Zr) nanoparticles, which enhanced the Zener drag pressure and delayed recrystallization. Grain boundary strengthening effects at various annealing temperatures were estimated using a constitutive equation. This work revealed that grain structure change and the corresponding boundary strengthening effect are key factors governing alloy strength evolution during annealing. Full article

This study explored the effects of T5 and T6 heat treatments on the microstructure and tensile properties of a laser powder bed fusion (LPBF)-fabricated Al–Mn–Mg–Sc–Zr alloy. The as-built condition exhibited a bi-modal grain structure of equiaxed and columnar grains. Specimens after T5 heat treatment also had a bi-modal microstructure with slight grain growth and the precipitation of secondary Al₃Sc, which enhanced the yield strength via precipitation hardening but reduced ductility. In contrast, T6 treatment triggered recrystallization, and the microstructure was only coarse equiaxed α-Al grains. This microstructure change was accompanied by coarsened primary Al₃X and Al₆(Mn, Fe) precipitates, partial Mg₂Si dissolution, and significant secondary Al₃Sc particle growth. Consequently, T6-treated specimens showed lower strength than their T5 counterparts and the poorest ductility due to brittle fracture induced by the stress concentration effect of coarse precipitates at grain boundaries. Full article

The aim of this study was to investigate the effect of the Sc/Zr ratio (Sc/Zr = 0.45–2.2) on the intergranular corrosion (IGC) resistance of Al–Mg alloys with different Mg content (2.5, 4, and 6%) and with a Sc + Zr = 0.32%. A change in the Mg concentration led to a change in the number of β-phase particles. A change in the Sc/Zr ratio led to a change in the composition of Al₃(Sc,Zr) particles. The IGC resistance of Al–Mg–Sc–Zr alloys was investigated by Tafel electrochemical tests and stationary tests. It has been demonstrated for the first time that two types of IGC defects appear during electrochemical tests. Large Type I defects were associated with the destruction of primary β-phase particles located along the dendrite boundaries. Fine Type II defects were associated with the grain boundaries (GBs). It has been demonstrated that during the stationary tests, Type I defects are formed. ECAP and subsequent annealing affect the ratio of the number of Type I and II defects. Increasing the Sc/Zr ratio reduced the depth of Type I defects, increased the fraction of Type II defects, and reduced the corrosion current density i_corr. It has been shown for the first time that the dependence of i_corr(T) had a three-stage character with a maximum at 450 °C in alloys with 2.5% and 4% Mg. A two-stage dependence of i_corr(T) is observed in alloys with 6% Mg. Increasing i_corr at T < 450 °C is due to the precipitation of the secondary β-phase particles on Al₃(Sc,Zr) particles and due to the effect of solid-phase wetting of the GBs by β-phase, which leads to an increase in the proportion of GBs containing thin layers of β-phase. Decreasing i_corr at T > 450 °C is associated with the dissolution of β-phase particles. Full article

High temperature tensile properties and long-term thermal stability play an important role in practical applications of Al-Zn-Mg-Cu alloys. In order to evaluate the effect of Er addition on the properties of an Al-Zn-Mg-Cu alloy as potential high temperature structural materials, the heat resistance properties of an Al-Zn-Mg-Cu alloy were investigated at various temperatures. After high temperature tensile testing and long periods of heat exposure testing, the microstructures of Al-Zn-Cu-Mg alloys with and without small Er addition is intentionally investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and quantitative transmission electron microscopy (TEM) characterization to explore the potential effect of Er on the tensile properties. The experimental results reveal that the heat resistance of T76-tempered Al-Zn-Cu-Mg alloy is obviously improved by adding trace Er. The Al₈Cu₄Er phase is found to segregate at the localized regions along grain boundaries and strengthens the grain boundaries at elevated temperatures. The η′ and η precipitation is obviously promoted by adding trace Er, and dispersed nano-sized Al₃(Er, Zr) precipitates were formed in the Er-containing alloys after homogenization, thereby enhancing the strength of Al-Zn-Mg-Cu. In addition, precipitates in both alloys gradually coarsen with the increase in thermal exposure temperature and the extension of thermal exposure time. The influence of precipitates on mechanical properties of the investigatived alloy after thermal exposure is also discussed. Full article

Transition element microalloying is important for improving the properties of Al-Zn-Mg-Cu alloys. Nevertheless, along with its high costs, increasing Sc content generates a harmful phase, limiting the strength of the alloy. In this experiment, we reduced the amount of Sc added to a Zr-containing Al-Zn-Mg-Cu alloy by one order of magnitude. The microstructure and mechanical properties of the alloys were studied by means of tensile tests, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The findings indicate that the alloys’ mechanical properties were progressively enhanced with the increase in Sc content from 0 to 0.04%. After adding 0.04% Sc, the tensile strength and yield strength of the Al-Zn-Mg-Cu-Zr-Sc alloy increased by 20.9% and 24.3%, reaching 716 MPa and 640 MPa, respectively, and the elongation decreased, but still reached 12.93%. The strengthening mechanisms of the trace addition of Sc are fine grain strengthening and precipitate and disperse strengthening, and Al₃(Sc, Zr) particles hinder the dislocation and grain boundary movement. Drawing on insights from other studies on Sc microalloying in Al-Zn-Mg-Cu alloys, this experiment successfully reduced the amount of Sc added by an order of magnitude, the alloys properties were improved, and the effect of strengthening remained good. Full article

In this paper, the microstructure changes of an Al–6.8Zn–2Mg–2Cu–0.1Zr–0.2Sc alloy for shipbuilding under different T6 states were investigated. The effect of aging temperature on the electrochemical corrosion behavior of the alloy was analyzed by means of SEM, EDS, and TEM, and the corrosion mechanism was revealed. The results show that the bean-shaped Al₃(Sc, Zr) phase is formed in the T6 alloy. The matrix-precipitated phase is mainly the GP zone at 120 °C. At 150 °C, part of the GP zone is transformed into the η′ phase, and at 180 °C, it is mainly η′ phase + η phase. After electrochemical testing in a 3.5 wt.% NaCl solution, it was found that the Cu content in the grain boundary η phase increased with the increase in aging temperature, the potential near the grain boundary increased, and the corrosion resistance increased. At the same time, the grain boundary precipitates were coarsened and distributed intermittently, which hindered the formation of corrosion channels and improved the corrosion resistance of the alloy. The corrosion mechanism of the alloy after aging at 120 °C/150 °C was mainly intergranular corrosion and pitting corrosion, while the corrosion mechanism after aging at 180 °C was mainly pitting corrosion. Full article

Superplastic forming is a process that enables the production of complex-shaped parts using metallic alloys. To design the optimal forming regimes and ensure the success of forming operations, it is essential to use mathematical models that accurately represent the superplastic deformation behavior. This paper is concerned with the study of the microstructure and superplastic deformation behavior, with the construction of a constitutive model, of Al-Mg-Zn-Cu-Zr aluminum alloys with varying Ni contents. The aluminum solid solution and coarse precipitates of the T(Mg₃₂(Al,Zn)₄₉ and Al₃Ni second phases were formed in the studied alloy and Cu dissolved in both second phases. The deformation behavior was investigated in the temperature range of 400–480 °C and the strain rate range of 10⁻³–10⁻¹ s⁻¹. Due to the fine Al₃Zr precipitates, the alloys exhibit a partially recrystallized grain structure before the onset of superplastic deformation. Coarse precipitates of the second phases facilitate dynamic recrystallization and enhance superplasticity at the strain rates and temperatures studied. The alloys with ~6–9% particles exhibit high-strain-rate superplasticity at temperatures of 440–480 °C and strain rates of 10⁻²–10⁻¹ s⁻¹. The presence of high fractions of ~9% Al₃(Ni,Cu) and ~3% T-phase precipitates provided high-strain-rate superplasticity with elongations of 700–800% at a low temperature of 400 °C. An Arrhenius-type constitutive model with good agreement between the predicted and experimental flow stresses was developed for the alloys with different Ni contents. Full article