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The effects of Sc, Mg and Si elements in an Al-Cu alloy have been studied by means of hardness tests and transmission electron microscopy analysis. The experimental results show that additions of Sc, Mg and Si can improve the heat resistance of the Al-Cu alloy. The Sc/Mg/Si segregation-sandwiched structure is the most stable, when compared with Sc segregation or Si/Sc co-segregation at the interface of θ′/Al. The additions of Si and Mg promote the aging–hardening response of the Al-Cu alloy. Mg is a micro-alloying element with great potential in stabilizing the size of θ′ phases, which further promotes the number density greatly. Consequently, the Al-Cu alloy achieves a high strength, matched with excellent thermal stability, due to the microalloying of Sc/Mg/Si solutes. [ABSTRACT FROM AUTHOR]

The Al–Mn alloy heat exchanger fin production process includes a brazing treatment at s high temperature of 600 °C, in which coarse grains are preferred for their high resistance to deformation at elevated temperatures by decreasing the grain boundary sliding. In this study, Al-1.57Mn-1.57Zn-0.58Si-0.17Fe alloy foils cold rolled by 81.7% (1.1 mm in thickness) and 96.5% (0.21 mm in thickness) were annealed at 100–550 °C for 1 h to investigate their recrystallization behavior, grain sizes, and precipitates by increasing the annealing temperature, using micro-hardness measurement, electron back-scattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The micro-hardness results showed that the recrystallization finishing temperatures for the two samples were almost the same, 323 ± 2 °C. The EBSD results showed that when the annealing temperature decreased from 550 to 400 °C, the recrystallized grain sizes of the two samples were nearly identical—both increased slightly. Further decreasing the annealing temperature from 400 to 330 °C caused the grain sizes to increase more, with the thinner foil sample having a more significant increase. The SEM and TEM observations showed that the micron-sized primary-phase remained unchanged during the annealing process. The nano-sized secondary phase precipitates formed during the hot-rolling process experienced a coarsening and dissolving process upon annealing. The particle size of the secondary phase increased from 32 nm to 44 nm and the area fraction decreased from 4.2% to 3.8%. The nucleation analysis confirmed that the large primary-phase could act as a nucleation site through particle stimulated nucleation (PSN) mode. The relatively dense secondary phase precipitates with small sizes at lower temperatures could provide higher Zener drag to the grain boundaries, leading to fewer nuclei and thereafter coarser grains. The coarsening of the recrystallized grains in the foils could be implemented through thickness reduction and/or precipitation processes to form densely distributed nano-sized precipitates. [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]

The thermodynamics of five Al3Er compounds were investigated through first-principles density-functional theory (DFT) and experimental analysis. The Al3Er compounds with Al3Ho.hR20 (prototype Al3Ho, Pearson symbol hR20), Cu3Au.cP4, AlNd3.hP8, Ni3Ti.hP16 and Al3Gd.hR12 structures exhibited formation energies of −0.412(−0.417), −0.411(−0.416), −0.400(−0.413), −0.399(−0.345) and −0.342(−0.345) meV/atom when using DFT with "standard" potential ("frozen core" potential) of Er. The results indicated that the Al3Ho.hR20 structure was the thermodynamic stable phase and the other structures were metastable. The formation energy of Cu3Au.cP4 structure was only 1 meV/atom less than that of Al3Ho.hR20. Experimentally, the Al-30 wt.% Er alloys were cooled from 900 °C to 500 °C at the rate of 5 ± 2 °C/h and 60 ± 2 °C/h, respectively. The corresponding XRD analysis showed that the Al3Ho.hR20 was formed at the cooling rate of 5 ± 2 °C/h and the Cu3Au.cP4 was formed at the cooling rate of 60 ± 2 °C/h, which indicated that the Al3Ho.hR20 was in a thermodynamic stable phase and the Cu3Au.cP4 was in a metastable phase with high stability. The structural analysis indicated that the tiny energy difference between Al3Ho.hR20 and Cu3Au.cP4 might be attributed to a similar structure with varied stacking sequences. [ABSTRACT FROM AUTHOR]

• Influence of Zn/Mg ratio on the microstructure and mechanical properties of Al-Zn-Mg alloys. • The hardness of the alloy with the Zn/Mg ratio of 2.38 aged was highest. • Spherical T′ phases was dominant in the three alloys. • Precipitates of alloys with Zn/Mg ratio of 1.61 and 3.93 significantly coarsened. The influence of Zn/Mg ratio on microstructure and mechanical properties of Al-Zn-Mg alloys with the same Zn + Mg contents has been investigated through microhardness test, electrical conductivity test and transmission electron microscopy (TEM). In this study, Zn/Mg ratio was changed from 1.61 to 3.93 with Zn + Mg content of 6 wt%. The results showed that the Vickers hardness of the alloy with the Zn/Mg ratio of 2.38 aged at 120 ℃ for 48 h was highest. Through TEM observation, strengthening precipitates in investigated alloys were mainly spherical T′ phases and a few plate-like η′ phases. With the increase of Zn/Mg ratio, T′ phase fraction in alloys decreased from 88% to 81%, and the corresponding η′ phase fraction increased from 12% to 19%. As aging at 120 ℃ from 48 h to 168 h, the coarsening degree of precipitates of alloy A and alloy C were both greater than that of alloy B. When the Zn + Mg content was 6 wt%, the alloy with the Zn/Mg ratio of 2.38 had optimum microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

The precipitation behaviors and thermal stability of Al-3.5Mg-1.0Cu alloys with co-addition of Zn and Si were investigated in this study. The results show that the addition of Zn to Al-Mg-Cu alloys enhances the age-hardening response because of the formation of T-Mg 32 (Al, Zn) 49 type phase, and the addition of Si further increases the peak hardness by refining the size of cube-like T phase. The majority of the cube-like T phases show the excellent thermal stability when aging at 175 ℃ while some T phases with low Cu content are coarsen seriously and transform to the lath-like shape. The addition of Si also enhances the thermal stability by narrowing the size distribution of precipitates. Two-step aging treatment leads a higher peak hardness but a deteriorative thermal stability. • The addition of Zn enhances aging hardening response due to the precipitation of T-Mg 32 (Al, Zn) 49 type phase. • Si increases peak hardness by refining the size of cube-like T phase. • The majority of cube-like T phase with high Cu proportion show excellent thermal stability. • Two-step aging treatment leads higher peak hardness but deteriorative thermal stability. [ABSTRACT FROM AUTHOR]

• The Al 3 (Er, Zr) particle exists in the initial material. • Saturated dislocations form dense dislocation walls. • Due to CDRX mechanism, the grains are refined to 2.8 μm at room temperature. • The (1 0 1) oriented coarse grains are relatively stable once they are formed. To obtain excellent mechanical properties, Al-Mg alloy was processed through a combination of equal channel angular pressing (ECAP) and micro-alloying techniques. In this study, the microstructural evolution of Al-Mg-Er-Zr alloy during ECAP at room temperature were systematically investigated. TEM results confirm that the Al 3 (Er, Zr) particle exists in the initial material and saturated dislocations form dense dislocation walls. The grains were refined with an average grain size of 2.8 μm after 4 passes of ECAP. Continuous dynamic recrystallization was identified and this mechanism led to the formation of fine grain structure. The (1 0 1)-oriented coarse grains were relatively stable once they had been formed. [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]

The aging behavior and the strengthening mechanism of the Si microalloyed Al–Zn–Mg–Cu alloy was investigated by means of microhardness tests, tensile properties tests and transmission electron microscope. It was found that the addition of Si element enhanced the microhardness and strength of Al–Zn–Mg–Cu alloy after aging at 125 °C, 175 °C and 225 °C. The age hardening effect of Al–Zn–Mg–Cu alloy gradually deteriorates with the increase of aging temperature, while the age hardening effect of Si-containing Al–Zn–Mg–Cu alloy at different aging temperature are stable. TEM results shows that the intragranular microstructure of the Si microalloyed alloy contained a fine dispersed, lath-like precipitate. This lath-like precipitation phase significantly improves the strength of the alloy and exhibit thermal stability, it is considered to be the GPB-II zone. [ABSTRACT FROM AUTHOR]

• Microalloying can improve the thermal stability of Al-Cu-Mg-Ag alloys. • Si addition reduces the amount of Ω phases. • Al-Cu-Mg-Ag-Sc alloy exists Al 3 Sc phases. • Sc atoms segregate to the θ' phase of Al-Cu-Mg-Ag-Si-Sc alloy. The competition between precipitation and segregation of Sc and its effects on thermal stability of Al-Cu-Mg-Ag alloys were investigated in this paper. Al-Cu-Mg-Ag-Sc has good thermal stability due to the precipitation of Al 3 Sc phases, but no segregation of Sc atoms on the interface of the Ω phases and the transformed θ' phases. Al-Cu-Mg-Ag-Si-Sc alloy has the best thermal stability due to Sc atoms segregate to the θ' phase thus inhibit the growth of the θ' phase. [ABSTRACT FROM AUTHOR]