Synergistic effect of gradient Zn content and multiscale particles on the mechanical properties of Al-Zn-Mg-Cu alloys with coupling distribution of coarse-fine grains

This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain struc-ture of the alloys,designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe(wt%)alloy with high strength and formability.With the increase of Zn content,forming the coupling distribution of multiscale precipitates and iron-rich phases with a reasonable matching ratio and dispersion distribution characteristics is easy.This phenomenon induces the formation of cell-like structures with alternate distribu-tion of coarse and fine grains,and the average plasticity–strain ratio(characterizing the formability)of the pre-aged alloy with a high strength is up to 0.708.Results reveal the evolution and influence mechanisms of multiscale second-phase particles and the corresponding high formability mechanism of the alloys.The developed coupling control process exhibits considerable potential,revealing remarkable improvements in the room temperature formability of high-strength Al–Zn–Mg–Cu alloys.

Effects of cryogenic treatment on the thermal physical properties of Cu_(76.12) Al_(23.88) alloy

The thermal diffusion coefficient, heat capacity, thermal conductivity, and thermal expansion coefficient of Cu76.12Al23.88 alloy before and after cryogenic treatment in the heating temperature range of 25℃ to 600℃ were measured by thermal constant tester and thermal expansion instrument. The effects of cryogenic treatment on the thermal physical properties of CU76,12A123,88 alloy were investigated by comparing the variation of the thermal parameters before and after cryogenic treatment. The results show that the variation trend of the thermal diffusion coefficient, heat capacity, thermal conductivity, and thermal expansion coefficient of CU76.12Al23.88 alloy after cryogenic treatment was the same as before. The cryogenic treatment can increase the thermal diffusion coefficient, thermal conductivity, and thermal expansion coeffi- cient of Cu76.12Al23.88 alloy and decrease its heat capacity. The maximum difference in the thermal diffusion coefficient between the before and after cryogenic treatment appeared at 400℃. Similarly, thermal conductivity was observed at 200℃.

Machine-learning-assisted prediction of the mechanical properties of Cu–Al alloy

The machine-learning approach was investigated to predict the mechanical properties of Cu–Al alloys manufactured using the powder metallurgy technique to increase the rate of fabrication and characterization of new materials and provide physical insights into their properties.Six algorithms were used to construct the prediction models, with chemical composition and porosity of the compacts chosen as the descriptors.The results show that the sequential minimal optimization algorithm for support vector regression with a puk kernel(SMOreg/puk) model demonstrated the best prediction ability. Specifically, its predictions exhibited the highest correlation coefficient and lowest error among the predictions of the six models. The SMOreg/puk model was subsequently applied to predict the tensile strength and hardness of Cu–Al alloys and provide guidance for composition design to achieve the expected values. With the guidance of the SMOreg/puk model, Cu–12Al–6Ni alloy with a tensile strength(390 MPa) and hardness(HB 139) that reached the expected values was developed.

Effect of Micro-scale Y Addition on the Fracture Properties of Al–Cu–Mn Alloy

Rare earth(RE) elements have positive e ects on Al alloy, while most research is focused on microstructure and mechanical properties. As important application indices, toughness and plasticity are properties that are sensitive to alloy fracture characteristics, and few research studies have characterized the fracture properties of Al–Cu–Mn alloy on RE elements. The e ect of di erent contents of Y on the fracture properties of Al–Cu–Mn alloy is investigated. T6 heat treatment(solid solution and artificial aging treatment), optical microscope(OM), scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS) methods are applied to the alloy. Results showed that when Y ele?ment is present at 0.1%, the section of the as?cast alloy has smaller sized dimples and the fracture mode presents duc?tile features. Slight changes in hardness are also observed and maintained at about 60 HV. With increasing content of the RE element Y from 0.1 to 0.5%, the θ phase and Cu atoms in the matrix were reduced and most stopped at Grain boundaries(GBs). Micro?segregation and an enriched zone of Y near the GBs gradually increased. At the same time, the inter?metallic compound AlCuY is aggregated at grain junctions causing deterioration of the micro?structure and fracture properties of the alloy. After T6 treatment, the flatness of the fracture surface was lower than that of all the as?cast alloy showing lots of dimples and teared edges with a significant increase in hardness. When Y content was 0.1%, the strength and hardness of the alloy increased due to refinement of the grain strengthening e ect. The content of Y elements segregated in the inter?dendritic zone and GBs is reduced. Plasticity and deformation compatibility also improved, making cracks di cult to form and merge with each other along adjacent grain junctions and providing an increased potential for ductile fracture. This paper proposes the addition of RE Y as an e ective and prospective strategy to improve the fracture properties of the Al–Cu–Mn alloy and provide a meaningful reference in terms of improving overall performance.

Influence of Si Contents on the Microstructure Evolution and Mechanical Properties of Al-Mg-Si-Cu-Zn Alloys

The influence of different Si contents on the microstructure evolution and mechanical properties of Al⁃Mg⁃Si⁃Cu⁃Zn alloys was systematically studied using tensile testing,OM,SEM,EDS,and EBSD.The results indicate that the grain size of as⁃cast alloys was gradually reduced with the increase of the Si content,which mainly resulted from the formation of many iron⁃rich phases and precipitates during the casting process.During homogenization treatment,the plate⁃likeβ⁃AlFeSi phases in the alloy with a higher Si content easily transformed to the sphericalα⁃Al(FeMn)Si phases,which is helpful for improving the formability of alloys.The microstructure evolution of the alloys was also greatly dependent on the content of Si that the number density and homogeneous distribution level of precipitates in the final cold rolled alloys both increased with the increase of the Si content,which further provided a positive effect on the formation of fine recrystallization grains during the subsequent solution treatment.As a result,the yield strength,ultimate tensile strength,and elongation of the pre⁃aged alloys in the direction of 45°with respect to the rolling direction were all increased with increasing Si content.

Cavitation Erosion Behavior of as-Welded Cu12Mn8Al3Fe2Ni Alloy

Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resistance ofthe as-welded Cu12Mn8Al3Fe2Ni alloy is much more superior to that of the as-cast one. The cumulative mass lossand the mass loss rate of the as-welded Cu12Mn8Al3Fe2Ni alloy are almost 1/4 that of the as-cast one. SEM analysisof eroded specimens reveals that the as-cast Cu12Mn8Al3Fe2Ni alloy is attacked more severely than the as-weldedone. Microcracks causing cavitation damage initiate at the phase boundaries.

Physical simulation of alloying between copper and aluminum on electrode tip for resistance spot welding of 5A02 aluminum alloy

The applicatio, n of aluminum alloy in the automotive and aviation fields is impeded by the wear and life of electrode for resistance spot welding （RSW）. The alloying interaction between the copper electrode and aluminum alloy sheet is the main reason of making electrode life decrease. The test of alloying interaction is difficult because of the transient in RSW of aluminum alloy. In this paper, the process of alloying between copper and aluminum on the electrode tip is simulated with Gleeble-1500 thermal simulation testing machine. The microstructure and composition of the sample of physical simulation for the alloying interaction between the copper electrode and aluminum alloy are analyzed using scanning electron microscope （SEM） and X-ray diffraction （XRD） respectively. The results indicate that the alloying reaction between copper and aluminum under the different temperature, pressure and time is mainly the eutectic reaction. The reaction result is the eutectic of （ Al ＋ CuAl2 ） , and then Cu9Al4 forms through solid diffusion between the CuAl2 phase and the copper base metal.

Cu/Li Ratio on the Microstructure Evolution and Corrosion Behaviors of Al–xCu–yLi–Mg Alloys

The microstructure evolution and the corrosion feature of Al–x Cu– y Li–Mg alloys( x : y = 0.44, 1.65 and 4.2) were systematically investigated under the same artificial aging conditions. The relationships between types of precipitates and mechanical performance, as well as electrochemical behaviors, were discussed. Our results show that different types of precipitates can be obtained in alloys with different Cu/Li mass ratios, which significantly influences the mechanical performance of the alloys and substantial corrosion behaviors. Specifically, the analogous corrosion evolution in the aging Al– x Cu– y Li–Mg alloys was first ascertained to be derived from the growth mechanism of the precipitates at the grain boundary(GB). Moreover, a small number of GB precipitates can be obtained in the aged alloy with the lowest Cu/Li mass ratio, thereby resulting in the largest intergranular corrosion resistance. A higher proportion of the GB T1 phase in the continuous precipitates induces higher corrosion sensitivity in alloy with a high Cu/Li mass ratio.

Microstructural evolution,dislocation density and tensile properties of Al–6.5Si–2.1Cu–0.35Mg alloy produced by different casting processes

Al–Si–Cu–Mg foundry alloys are used in casting process technologies.However,their strength properties remain low due to their microstructural characteristics and porosity.In this work,the microstructural characteristics,dislocation densities,and mechanical properties of Al–Si–Cu–Mg cast alloys prepared through different casting methods were studied experimentally.Four casting processes,namely,gravity casting(GC),rheocasting(RC),thixoforming(Thixo),and Thixo with heat treatment,were used.The GC and RC samples had mainly dendriticα-Al phase microstructures and exhibited coarse Si particles and intermetallic compounds in their interdendritic regions.By contrast,the Thixo and heat-treated Thixo(HT-Thixo)samples exhibited microstructural refinement with uniformly distributedα-Al globules,fine fibrous Si particles,and fragmented intermetallic compounds amongα-Al globules.The accumulation of dislocation densities increased in the Thixo sample as the strain was increased due to plastic deformation.Furthermore,the ultimate tensile strength and yield strength of the HT-Thixo sample increased by 87%and 63%,respectively,relative to those of the GC sample.The cleavage fracture displayed by the GC and RC samples led to brittle failure.Meanwhile,the Thixo and HT-Thixo samples presented dimple-based ductile fracture.

Solidification behavior and elimination of undissolved Al_(2)CuMg phase during homogenization in Ce-modified Al–Zn–Mg–Cu alloy

The solidification behavior and intermetallic phase evolution during homogenization annealing of an Al-Zn-Mg-Cu alloy with 0.12 wt%Ce addition were examined.The residual Al_(2)CuMg phase is completely dissolved after homogenization and is replaced by a large number of dispersed micro/nanoscaled AlCuCe enrichment phases within Al matrix.This change occurs because of the formation of a large number of finer lamellar eutectic network structures which are more easily dissolved into Al matrix during the homogenization process.In addition,the trapping of Cu atoms in the stable AlCuCe phase also prevents the formation of Al_(2)CuMg phase,leading to the complete dissolution of Al_(2)CuMg phase in the Al-Zn-MgCu alloy.The grain refinement behavior in Al alloy with Ce addition is similar to that in alloys with the addition of Sc,because of the formation of primary Ce-enriched Al_(11)Ce_(3)phase as the nucleation agent ofα(Al)during solidification.

Distribution uniformity of added elements in twin-roll cast Al–Zn–Mg–Cu alloy by multi-electromagnetic fields

The micromorphology and the concentration o massive precipitates produced by twin-roll casting(TRC processes without and with multi-electromagnetic fields fo Al–Zn–Mg–Cu alloy at 670 °C were investigated in detai by means of optical microscopy(OM) and electron probe micro analyzer(EPMA). The results clearly show tha under a 0.2 T static magnetic field, the macro-segregation bands are remarkably alleviated according to the order o uniform static magnetic field, half-wave oscillating elec tromagnetic field as well as alternating oscillating elec tromagnetic field, as compared with the non-field TRC process(B = 0). Moreover, under the alternating oscillat ing electromagnetic TRC process, almost all segregation bands disappear. Additionally, through the observation on a smaller scale, the netlike precipitates elongated and broken by electromagnetic force, and replaced by numerous bulk depositions. EPMA analysis shows that the added atoms are diffused from deposition to a(Al) matrix, resulting in that the solute concentration in and around the precipitates is tending toward uniformity and stability.

Phases and microstructures of high Zn-containing Al–Zn–Mg–Cu alloys

Phases and microstructures of three high Zncontaining Al–Zn–Mg–Cu alloys were investigated by means of thermodynamic calculation method, optica microscopy（OM）, scanning electron microscopy（SEM）energy dispersive spectroscopy（EDS）, X-ray diffraction（XRD）, and differential scanning calorimetry（DSC） analysis. The results indicate that similar dendritic network morphologies are found in these three Al–Zn–Mg–Cu alloys. The as-cast 7056 aluminum alloy consists of aluminum solid solution, coarse Al/Mg（Cu, Zn, Al）2 eutectic phases, and fine intermetallic compounds g（MgZn2）. Both of as-cast 7095 and 7136 aluminum alloys involve a（Al）eutectic Al/Mg（Cu, Zn, Al）2, intermetallic g（MgZn2）, and h（Al2Cu）. During homogenization at 450 ℃, fine g（MgZn2） can dissolve into matrix absolutely. After homogenization at 450 ℃ for 24 h, Mg（Cu, Zn, Al）2 phase in 7136 alloy transforms into S（Al2Cu Mg） while no change is found in 7056 and 7095 alloys. The thermodynamic calculation can be used to predict the phases in high Zncontaining Al–Zn–Mg–Cu alloys.

Effects of Solution Treatment on the Microstructure,Tensile Properties,and Impact Toughness of an Al–5.0Mg–3.0Zn–1.0Cu Cast Alloy

This study investigates the eff ect of solution treatment(at 470°C for 0–48 h)on the microstructural evolution,tensile properties,and impact properties of an Al–5.0Mg–3.0Zn–1.0Cu(wt%)alloy prepared by permanent gravity casting.The results show that the as-cast microstructure consists ofα-Al dendrites and a network-like pattern of T-Mg32(AlZnCu)49 phases.Most of the T-phases were dissolved within 24 h at 470℃;and a further prolonging of solution time resulted in a rapid growth ofα-Al grains.No transformation from the T-phase to the S-Al2CuMg phase was discovered in this alloy.Both the tensile properties and impact toughness increased quickly,reached a maximum peak value,and decreased gradually as the solution treatment proceeded.The impact toughness is more closely related to the elongation,and the relationship between impact toughness and elongation appears to obey an equation:IT=8.43 EL-3.46.After optimal solution treatment at 470℃for 24 h,this alloy exhibits excellent mechanical properties with the ultimate tensile strength,yield strength,elongation and impact toughness being 431.6 MPa,270.1 MPa,19.4%and 154.7 kJ/m^(2),which are comparable to that of a wrought Al–6.0 Mg–0.7 Mn alloy(5E06,a 5 xxx aluminum alloy).Due to its excellent comprehensive combination of mechanical properties,this cast alloy has high potential for use in components which require medium strength,high ductility and high toughness.

Synchronously Improving the Thermal Conductivity and Mechanical Properties of Al–Si–Fe–Mg–Cu–Zn Alloy Die Castings Through Ultrasonic-Assisted Rheoforming

An ultrasonic vibration-assisted air-cooled stirring rod process(ACSR+UV)was used to efficiently prepare a large-volume semisolid slurry with a mass of more than 40 kg.A low-cost Al–Si–Fe–Mg–Cu–Zn die-casted alloy with high thermal conductivity,high plasticity and medium strength was developed.The alloy was used to manufacture large,thin-walled parts for 5 G base stations by using the ACSR+UV rheological die-casting(ACSR+UV R-DC)process.Investigations were performed on the microstructure,porosity,mechanical properties,fracture behaviour and thermal conductivity of the ACSR+UV R-DC alloy,which was then compared to traditionally die-casted(T-DC)and ACSR R-DC alloys.The mechanisms for the microstructural refinement and enhancement of the mechanical and thermal conductivity performances of the ACSR+UV R-DC alloy were also analysed.The results showed that the ACSR+UV process increased the nucleation rate of the melt due to the increase in the nucleation area and the generation of cavitation bubbles.A radial-and an axial-forced convection was also generated inside the melt under the combined effects of acoustic flow and mechanical stirring,thereby homogenising the melt composition field and the temperature field.Therefore,the ACSR+UV R-DC process not only refined the primaryα-Al(α_(1)-Al),the eutectic silicon and the secondaryα-Al(α_(2)-Al),but also greatly improved the morphology and the distribution of the β-Al5FeSi phase.The mechanical properties of the ACSR+UV R-DC alloy were higher than those of the T-DC and the ACSR R-DC alloys.Compared to the T-DC alloy,the ultimate tensile strength,elongation and yield strength of the ACSR+UV R-DC alloy were increased by 34%,122%and 19%,respectively.This was because the ACSR+UV R-DC technique gave the alloy the characteristics of high density,fine sphericalα1-Al grain and a fine and uniform β-phase,which improved the fracture behaviour of the alloy.The thermal conductivity of the ACSR+UV R-DC alloy was 184 W/(m K),which was 10.2%and 3.4%higher than that of T-DC and ACSR R-DC alloys,respectively.This was because the refined eutectic silicon and β phases in the ACSR+UV R-DC alloy facilitated an easier electron flow through the eutectic region,and the decrease in porosity increased the effective area of heat conduction.

Cytotoxicity of Ti–6Al–4V–5Cu Alloy to MC3T3-E1 Cells

The aim of this work was to study the cytotoxicity of Ti–6 Al–4 V–5 Cu(TC4–Cu)alloy for dental applications and evaluate the cell viability of diff erent fabricated TC4–Cu alloys in contact with MC3 T3-E1 cells in vitro.Ti–6 Al–4 V(TC4)alloy was used as a negative control to evaluate the cytotoxicity level of TC4–Cu alloy so as to provide basic support for the dental clinical application.Control group TC4 and experimental group TC4–Cu with diff erent fabrications were incubated in the cell culture medium.The absorbance value of mouse osteoblast MC3 T3-E1 cells was detected by CCK-8 assay after 1,3 and 7 days,respectively.The relative proliferation rate of cells was calculated,and then the toxicity level was valued for each group.Cell morphology on the surface was also studied by observing the cytoskeleton through F-actin filament staining.The experimental results showed that the absorbance values for the experimental and the negative control groups were not same at diff erent time points.Compared with diff erent fabricated TC4–Cu alloys,the annealing-TC4–Cu alloy showed much better biocompatibility.The mouse osteoblast MC3 T3-E1 cells cultured with annealing-TC4–Cu,rolling-TC4–Cu and solution+aging-TC4–Cu have no toxic eff ects,and these alloys could promote the proliferation of mouse osteoblasts.

Quantitative Electron Tomography for Accurate Measurement of Precipitates Microstructure Parameters in Al–Cu–Li Alloys

Mechanical theories show that properties of alloys are strongly dependent on the morphological parameters oftheir strengthening precipitates.However,accurate measurement of precipitates microstructure parameters is still a challenging task.In this article,we develop a quantitative electron tomography method by combining computer vision technology to accurately characterize the three-dimensional microstructure parameters,such as volume fractions,sizes and distributions,of the T_(1) and δ’/θ’/δ’ precipitates in Al-Cu-Li(-Mg) alloys.Since they have extremely large aspect-ratios in shape and large numbers in density upon formation in the Al matrix,these thin plate-like precipitates are difficult to be characterized quantitatively without the assistance of computer vision technology.It is shown that the property difference between two peak-aged states of the alloy can be well explained with the quantitative precipitate parameters correctly measured.Using these correct precipitate data,we also tested the validity of current mechanical models for projecting the contribution of precipitates to the strengths of the alloy,demonstrating that quantitative relations between strength and micro structure parameters still need to be refined.

Technological Aspect of Processing Maps for the AA2099 Alloy

Results of an experimental and modelling study of forming processes in the AA2099 Al–Cu–Li alloy, for a wide range of temperatures, strains and strain rates, are presented. The analyses are based on tensile testing at 20 °C at a strain rate of 0.02 s-1and uniaxial compression testing in the temperature range 400–550 °C at strain rates ranging from0.001 to 100 s-1, for constant values of true strain of 0.5 and 0.9. The stability of plastic deformation and its relationship with a sensitivity of stress to strain rate are considered. The power dissipation efficiency coefficient, g（%）, and the flow instability parameter, n B 0, were determined. The complex processing maps for hot working were determined and quantified, including process frames for basic forging processes： conventional forging and for near-superplastic and isothermal conditions. A significant aspect is the convergence of power dissipation when passing through the 500 °C peak.Deformation, temperature and strain-rate-dependent microstructures at 500 °C for strain rates of 0.1, 1, 10 and 100 s-1are described and analysed for the conventional die forging process frame, corresponding to 465–523 °C and strain rates of50–100 s-1.

In Situ Aluminum Alloy Coating on Magnesium by Hot Pressing

In the present study, pure magnesium was in situ coated with pre-alloyed Al–Cu–Mg alloy through hot pressing. The produced samples were characterized by means of hardness, wear properties and microstructure characterization. A ball-on-disk test was used to determine the dry sliding wear characteristics of the compacts. The results showed that the hot pressing technique has been successfully applied for producing magnesium parts with compatible wear resistance and hardness to aluminum. The in situ coating of Al on Mg by hot pressing resulted in an increase in hardness of about 30% compared with the pure Mg substrate. The wear rate and friction coefficient of the samples decreased with Al coating and increased with an increase in the applied load during the wear tests, compared with the uncoated material.