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Microalloying has been an important method in aluminum alloy development for decades. Large number of papers have shown that the addition of trace element Erbium (Er) can effectively improve the comprehensive properties of aluminum alloys. Similar with the trace element Scandium (Sc), addition of trace element Er in aluminum alloys could form nano-sized L12-ordered Al3Er precipitates, which was coherent with the Al matrix. However, the dispersion precipitation strengthening effect of Al3Er was more significant than that of Al3Sc, at the same atomic content. In the case of the addition of both Er and Zr, core–shell-structured Al3(Er, Zr) precipitates formed instead of Al3Er precipitates. Those thermally-stable nanosized precipitates could significantly refine the grain size, retard the recrystallization, improve the mechanical properties and corrosion resistance. This paper reviewed several typical Er-containing microalloyed commercial aluminum alloys, like 2xxx (Al–Cu) alloys, 4xxx (Al–Si) alloys, 5xxx (Al–Mg) alloys, 7xxx (Al–Zn–Mg–Cu) alloys, as well as selective laser melting aluminum alloys. [ABSTRACT FROM AUTHOR]

A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. [ABSTRACT FROM AUTHOR]

Rare earth elements and transition elements are widely used in aluminum alloys, magnesium alloys and copper alloys due to their unique microalloying effects. With regard to in-depth research on the grain refinement characteristics of rare earth elements and transition elements, the combination of grain refinement and microalloying in the master alloys has a great impact on the theories and technical research of refinement, and the broadening of the application field of master alloys. This paper first summarizes the grain refinement mechanisms and analyzes the effects of rare earth elements and transition elements on the grain refinement of aluminum and aluminum alloys, and summarizes the elements suitable for the preparation of Al-M master alloys and their refinement mechanism. [ABSTRACT FROM AUTHOR]

An argon TIG welded joint of the Al - Zn -Mg - Cu alloy was studied. Based on the hardness and differential scanning calorimetry studies, a post-weld alloy heat treatment regimen has been proposed to ensure a welded joint strength of 622 MPa versus the strength of the base metal of 676 MPa. The post-weld heat treatment provides for a two-stage solid solution treatment (470°C, 90 min + 500°C, 20 min) and artificial aging at 120°C for 24 h. [ABSTRACT FROM AUTHOR]

The healing kinetics of nanometer-scale voids in Al-Mg-Er and Al-Mg-Zn-Er alloy systems were investigated with a combination of in situ transmission electron microscopy and electron tomography at different temperatures. Mg was observed completely healing the voids, which were then rejuvenated to the alloy composition with further aging, in the Al-Mg-Er alloy. On the contrary, MgZn intermetallic compound was formed in voids in the Al-Mg-Zn-Er alloy, which leads to complete filling of the voids but not rejuvenation for the material. For voids with different geometrical aspects, different evolution processes were observed, which are related to the competition between bulk and surface diffusion of the alloys. For voids with a large size difference in their two ends, a viscous flow of surface atoms can be directly observed with in situ electron microscopy, when the size of one end becomes less than tens of nanometers. [ABSTRACT FROM AUTHOR]

Abstract: The annealing behavior of a modified 5083 aluminum alloy was studied in the temperature range of 125–375°C with different holding times. The results shown that the annealing temperature was more sensitive to the mechanical and corrosion resistance properties compared with the annealing holding time. The mechanical and corrosion resistance properties depend on annealing treatment due to different dislocation configuration in the matrix and the second phase interface, annealing temperature and time have been optimized for both of those properties improvement. [Copyright &y& Elsevier]

• A modified Gurson-Tvergaard-Needleman (GTN) model has been established for predicting ductile fracture in high strain rate conditions for alloys. • The improved GTN model predicts results for 7xxx aluminum alloys consistent with Taylor impact fracture test results. • The strength of the material within the shear damage zone may experience a subsequent increase after an initial decrease. The Gurson-Tvergaard-Needleman (GTN) model has been improved to extend its application for high strain rate loading and assessed by using the Taylor impact process of 7xxx aluminum alloys. The existing modification method based on independent shear damage variables has been integrated into the enhanced GTN model to assess shear fracture. In addition, the effects of strain rate hardening, temperature softening, and viscosity resistance terms have been taken into account in the constitutive equation to accurately depict the material's deformation behavior under high strain rates. A series of quasi-static mechanical tests and Split Hopkinson Pressure Bar (SHPB) tests with strain rates ranging from 1000 s - 1 ∼ 5000 s - 1 were conducted on 7A52-T6 alloy and 7A62-T6 alloy. The Taylor impact experiments showed that the mushrooming deformation and shear fractures occurred as the impact velocity increased. Both the 7A52 and 7A62 alloys exhibited fracture characteristics of shear and void nucleation, and the voids only grew slightly after formation. The predicted fracture patterns in Taylor impact and the evolution trend of material strength using the enhanced GTN model are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

• The modified GTN model accurately predicts the impact failure mode. • Laminated plates in specific combinations can mitigate the risk of fragment impact. • The mechanism of impact failure is clarified through microstructural characterization. • Laminated plates enhance ballistic resistance against blunt nosed and deformable projectiles. • The laminated plate increasing the plastic deformation capacity after spalling failure. The ballistic impact of two 7XXX aluminum alloys, 7A52-T6 and 7A62-T6, as well as their combination in a 7B52 laminate plate, was simulated and experimentally tested. Three types of projectiles were utilized hard ogival nosed, hard blunt nosed, and 304 steel core projectiles to investigate the ballistic resistance and failure mechanisms of the aluminum alloy targets. Additionally, an existing modified Gurson-Tvergaard-Needleman (GTN) model incorporating shear, void growth, and spalling failure mechanisms, was employed to simulate the ballistic impact process, utilized to analyze energy dissipation during impact. The results reveal that the 7A52 alloy only experiences ductile hole expansion failure, whereas the 7A62 high-strength aluminum alloy undergoes spalling and fragmentation subsequent to penetration, leading to potential impact hazards. Due to its backing layer being the highly ductile 7A52 alloy, the laminate plate will not produce fragments after penetration. The improved GTN model provided better predictions of the impact failure modes of the aluminum alloys. Concerning impact performance, when subjected to hard ogival projectiles, the laminate alloy did not enhance material impact resistance. However, when impacted by blunt-nosed projectiles, the laminate alloy exhibited a 27 % improvement over the 7A52 plate and an 11.9 % increase over the 7A62 plate. Furthermore, when impacted by 304 steel core ogival projectiles, the laminate alloy demonstrated over a 41.3 % improvement compared to the 7A52 plate and over a 15.5 % increase compared to the 7A62 plate. The laminate plate's high ballistic performance was attributed to the increased plastic deformation energy after spalling failure, while ensuring high energy absorption during ductile hole expansion penetration. [ABSTRACT FROM AUTHOR]

An abnormal reverse transition of intergranular corrosion from sensitization to stabilization was observed in the Al-6.4 Mg-0.43Mn-0.37Er-0.17Zr alloy at low annealing temperatures between 220 and 260 °C for the first time. The reverse stabilized alloy annealed at 240 °C for 5 h had excellent long-term corrosion resistance in the deformed state. The corresponding transmission electron microscopy analysis showed that Al 3 Mg 2 precipitates distributed separately along grain boundary, at triple junctions and the Al 6 Mn phase boundary. The combination of the low temperature reverse stabilization and retarded recrystallization by addition of Er and Zr caused the high Mg aluminum alloy to exhibit high corrosion resistance and strain hardening. Unlabelled Image [ABSTRACT FROM AUTHOR]

[Display omitted] • Increasing Er content could reduce crack density in Al-Mg alloy fabricated by laser powder bed fusion. • Al 3 Zr particles with L1 2 structure promote the formation of equiaxed grains and refine the grain size. • Er-Zr synergistic effect promotes the precipitation of Al 3 (Er,Zr) and improves the tensile properties during aging treatment. • The Al-6Mg-0.7Mn-0.4Er-1.2Zr alloy has a strength of more than 500 MPa after heat treatment and has a cost advantage. This paper centers on high-strength Al-Mg-Mn-Er-Zr alloy, which was developed through the addition of Er, a cheap rare earth element, and suitable for additive manufacturing (3D printing). The microstructure and mechanical properties of Al-Mg-Mn-Er-Zr alloy of as-built and heat treated samples have been characterized, which shows: the precipitation of Al 3 Zr primary phase at the boundary of molten pool promotes heterogeneous nucleation and refines the grains, which suppresses the formation of solidification cracking in Al-Mg alloy. To bring the Er-Zr synergistic effect into play during the aging heat treatment, the nano-scale precipitation phase of Al 3 Er that diffuses nucleation at an earlier stage promotes the precipitation of Zr, leading to the formation of Al 3 (Er,Zr) core-shell structure and enhancing precipitation strengthening effect. Under the combined effects of multiple strengthening mechanisms, the yield strength could reach 440 ± 3 MPa; tensile strength, 520 ± 2 MPa and elongation 15.5 ± 1.0 %. [ABSTRACT FROM AUTHOR]

Samples made of a super high strength aluminum alloy with high Zn content were friction stir welded with rotation rates of 350–950 rpm and welding speeds of 50–150 mm/min. The effect of welding parameters on the microstructure and mechanical properties was investigated. It was observed that the grain size of the nugget zones decreased with the increasing welding speed or the decreasing tool rotation rate. Most of the strengthening precipitates in the nugget zone were dissolved back and the intragranular and grain boundary precipitates in the heat affected zone coarsened significantly. The greatest ultimate tensile strength of 484 MPa and largest elongation of 9.4 were obtained at 350 rpm−100 mm/min and 350 rpm−50 mm/min, respectively. The ultimate tensile strength and elongation deteriorated drastically when rotation rate increased from 350 to 950 rpm at a constant welding speed of 100 mm/min. [ABSTRACT FROM AUTHOR]

In this work, Al-0.88Er-0.78Zr (wt%) alloy was fabricated via laser powder bed fusion (LPBF). The microstructure, precipitates distribution, electrical conductivity and hardness of as-built and aging treatment specimens were carefully characterized. Results show that LPBF process greatly expand the solid solubility of Er and Zr in Al. The addition of Er can significantly refine the grain size and form a bimodal grain structure consisting of fine equiaxed grains (grain size ~0.53 ± 0.15 µm) at the boundary of molten pool together with coarse columnar grains (width 2.57 ± 0.84 µm) at the center of molten pool. After 375 ℃ for 3 h aging treatment, the particles on the grain boundary inhibit the grain growth; at the same time, a large number of Al 3 (Er,Zr) particles with L1 2 structure and size of 2.25 ± 0.3 nm are precipitated, which plays a major role in enhancing the hardness with the peak hardness of about 89.24 ± 3.77 HV. Er and Zr elements are proved to be an alternative way of the additive elements for developing a new 3D printing high-strength aluminum alloy. [Display omitted] • The co-addition of Er and Zr provides grain refinement on Al-alloy fabricated by LPBF. • Al 3 (Er,Zr) precipitates provide heterogeneous nucleation sites leading to a unique bimodal grain structure. • LPBF process expands the solid solubility of Er and Zr in the aluminum matrix. • Nano-sized Al 3 (Er,Zr) precipitates play a major strengthening role on artificial aged alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] The critical radius of Al3Er from coherent to semi-coherent was 8.0–9.1nm. [•] The diffusion activation energy of Er in Al was evaluated to be 77.2±5.3kJ/mol. [•] The misfit of Al3Er with matrix would be reduced at small particle range. [•] The APB energy of Al3Er was estimated to be about 0.60±0.03J/m2. [ABSTRACT FROM AUTHOR]

Highlights: [•] The solvuses of Er and Yb in Al were evaluated from thermodynamic analysis of solubilities. [•] The largest volume fractions of Al3Er and Al3Yb were 0.16% and 0.1%, respectively. [•] The evaluation of nucleation rates implied a much denser fine precipitates in Al–Er or Al–Yb alloys. [ABSTRACT FROM AUTHOR]

Abstract: Samples of Al–Mg–Mn–Zr–Er alloys have been welded using the method of TIG welding. Microstructures characterization was performed by optical microscopy (OM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM), respectively. In addition, tensile and hardness test was conducted. The relationship between mechanical properties and microstructure of welded joints is evaluated. Results indicate that the ultimate tensile strength of the joints is 72% of that of the base metal. The base metal consists of a typical rolled structure, and the fusion zone (FZ) is mainly made up of dendrite grains. A characteristic equiaxed zone (EQZ) is obtained at the fusion boundary between the base metal and fusion zone. Fine dispersion of coherent Al3Er precipitates was found in the base metal, however, the quantity of these particles dropped significantly in the fusion zone. The hardness test results indicate that the microhardness in the fusion zone is lower than that of the base metal, due to the as-cast structure in this region. Based on the present work, it is concluded that TIG welding is the suitable welding procedure for joining this new type Er-containing aluminum alloy. [Copyright &y& Elsevier]

The effect of stabilization annealing on the long-term corrosion resistance and microstructure in Er and Zr contained 5083 aluminum alloy was studied using the nitric acid mass loss test (NAMLT), exfoliation corrosion (EC) test, accelerated sensitization annealing (ASA) at 175 °C and transmission electronic microscopy (TEM) observation. The results showed that the alloy in cold rolling state sensitized severely after the ASA. The long-term IGC and EC resistances improved significantly through stabilization treatment at 220 °C. The longer stabilization time, the better long term corrosion resistance. The precipitation evolution of the alloy during the ASA in cold rolling state and stabilization state were analyzed by TEM. The results showed that the β precipitates were not found at cold rolling state, but formed continuously along grain boundary during ASA at 175 °C for 2 h. After 12 h stabilization treatment from the cold rolling sample, β precipitates were isolated at the triple junctions and Al 6 (Mn,Fe) phase boundaries. During the further ASA at 175 °C for 2 h, β phases formed sparsely and separately at grain boundaries. The addition of stabilization treatment led to the morphology change of β phases during ASA, resulting in the improvement of long-term IGC resistance. Its mechanism was discussed thermodynamically and kinetically. Unlabelled Image • Effect of stabilization on corrosion and microstructure was studied in Er-contained AA5083. • Long-term corrosion resistance improved significantly by stabilization at 220 °C. • During direct sensitization, β phase was thin and continuous along grain boundary. • During sensitization after stabilization, β phase was separated sparse at grain boundary. [ABSTRACT FROM AUTHOR]

The intergranular corrosion and β phase evolution of 5083 aluminum alloy containing Er and Zr during annealing at 100–230 °C were studied using mass loss tests and transmission electron microscopy. The mass loss curves showed that when annealing temperature changed from 200 to 220 °C, the alloy was subjected to a transition from sensitized state to stabilized state, corresponding to the change of nucleation position of β precipitates from grain boundaries to triple junctions. Particularly, when the annealing temperature was at 210 °C, this transition could also happen when the annealing time was increased from 0.5-10 h to 15-24 h, associated with the change in the shape of β precipitates. The classical nucleation analysis with the consideration of Mg segregation showed the nucleation rates at grain boundary and triple junction were 1013 and 1011 m−3 s−1 at sensitization temperature 150 °C, but 109 and 1010 m−3 s−1 at stabilization temperature 220 °C, suggesting the change of nucleation site with increasing temperature. The analysis of diffusion flux of Mg around β precipitate suggested that the shape change of β precipitates from elongate to spheroidal at 210 °C was attributed to the dominant interface diffusion over the grain boundary diffusion with the increase of time. Unlabelled Image • The intergranular corrosion and microstructure in 5083 alloy with Er and Zr upon annealing were systematically studied. • The transition of sensitized to stabilized state was attributed to different nucleation locations of β phase at 200-220°C. • The sensitization and reversal process at 210°C was attributed to elongation and spheroidization of grain boundary β phase. • The nucleation rate and the morphology evolution of β phase along grain boundary were intensively discussed. [ABSTRACT FROM AUTHOR]