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Abstract Al–Si–Mg alloys manipulated by in-situ synthesized nanoparticles have been prepared by casting method in this work. The addition of different contents of refiners promoted the obvious grain refinement of the Al–Si–Mg alloys. It was found that 0.10 wt% refiners addition caused a significant and efficient refinement on α-Al (from 1675 µm to 199 µm) and Mg 2 Si in the inoculated Al–Si–Mg alloys. The morphology of the eutectic Si in the inoculated Al–Si–Mg alloys transformed from needle-like structure to a fibrous one, and the mean size sharply decreased (from 26.56 µm to 11.89 µm) and increased a little with the increase of FeBSi amorphous refiners content. Tensile property tests showed that both strength and ductility of the alloys were improved by the addition of FeBSi amorphous refiners. The yield strength, tensile strength, fracture strain and elongation of the alloy inoculated with 0.10 wt% FeBSi amorphous refiners for 20 min were 226 MPa, 343 MPa, 18.4% and 16.7%, compared to those of the uninoculated alloy (170 MPa, 289 MPa, 13.7% and 12.2%), respectively. It was found that the Fe 2 B and Fe 3 Si nano-sized particles which were crystallized from FeBSi amorphous refiner contributed to the grain refinement of α-Al, resulting in higher strength. Moreover, grain refinement shortened the atomic diffusion distance and refines Mg 2 Si. The grain refinement and spheroidization of eutectic Si enhance uniform deformation during tension, and reduce the possibility of crack initiation and expansion, thus improving the plasticity. Graphical abstract fx1 Highlights • The inoculated Al–7Si–0.3Mg alloy appeared as 199 µm fine grains. • The inoculated alloy reached 226 MPa, 343 MPa, 18.4%(δ) and 16.7%(ε f). • This work achieved the refinement of α-Al and Mg 2 Si and the spheroidization of eutectic Si. • The Fe 2 B, Fe 3 Si had better lattice mismatch with α-Al and eutectic Si. [ABSTRACT FROM AUTHOR]

Insufficient performance, especially at high temperatures, limits the extensive application of cast Al–Cu alloys. This study proposes a novel method of direct reaction synthesis (DRS) for the simultaneous synthesis and dispersion of hybrid-sized in situ TiC–TiB 2 particles in the melt to prepare a trace-particle-reinforced high-performance cast Al–Cu 5.5 –Mn 0.45 –Ti 0.3 –V 0.3 –Cr 0.2 –Zr 0.14 –B 0.04 alloy. The particulate-reinforced alloy achieved strength–ductility synergetic enhancement at room and high temperatures. In comparison to the Al–Cu matrix alloy, the yield strength of 0.7 wt% (TiC–TiB 2)/Al–Cu alloy at 298 K (529 MPa), 493 K (214 MPa), and 533 K (183 MPa) had an increase of 28%, 18% and 35%, meanwhile their elongation increased by 4%, 50% and 62%, respectively. The yield strength enhancement primarily benefited from the thermal mismatch between the particles and matrix, and Orowan strengthening. The strength–ductility performance improvement is due to the optimization of the microstructure: significantly refined α-Al grains with smaller and more dispersed θʹ precipitates. Further, the improvement mechanism of the microstructure is due to the action of the nanoparticles on the heterogeneous nucleation stimulation and dendrite growth inhibition of α-Al during the solidification process. Meanwhile, the segregation of the Cu atoms was inhibited by the particles. The precipitation was significantly promoted because of more uniformly distributed Cu atoms, and more defects induced by particles improved diffusion of the Cu atoms the number and density of the precipitation sites. The results of this study provide an economical and accessible synthesis strategy for industrial manufacturing. [ABSTRACT FROM AUTHOR]

We report a new rolling route combining one pass of hard-plate rolling and two passes of conventional rolling. This route is efficient in achieving near-spherical Mg 17 Al 12 phase (~0.5 µm) and uniform fine-grained structure (~3 µm) featuring a weakened texture in AZ91-0.4Sn plates after a total thickness reduction of ~86.4% via 3 rolling passes. Moreover, the processed alloy exhibited superplasticity-like fracture strain of ~96% at 200 °C, owing to fine α-Mg grains distributed with a high volume fraction of Mg 17 Al 12 . This new route significantly reduces rolling passes and hence has a great potential for industrial production. [ABSTRACT FROM AUTHOR]

Adding alloying elements to increase precipitation is a common method to strengthen aluminum (Al) alloys, but an excessively high alloying element content causes segregation and a reduction in plasticity. In this work, the tradeoff between alloying element content and segregation was explored along with the simultaneous increase in precipitation and dislocation density under the action of trace TiB 2 +TiC particles with the aim of giving a full play to the strengthening effect of dislocation and precipitation and maximizing the strength and toughness of the alloy. The cast Al–Zn–Mg–Cu alloys contained various alloying elements (Zn, Mg), and the alloys were reinforced with 0.5 wt% TiB 2 +TiC particles via in-situ reaction in the Al melt. The TiB 2 +TiC particles blocked the diffusion of the alloying elements and inhibited segregation, promoting solution of alloying elements and yielding dispersed and finer precipitates after solution and aging. Meanwhile, owing to the difference in the thermal expansion coefficients of the matrix and particles, the dislocation density of the alloy doubled. Therefore, the yield strength, elongation, and the product of the tensile strength and elongation of the Al-6.60Zn-3.15Mg-1.60Cu alloy with particles reinforcement were 562 MPa, 4.5%, and 3163 MPa·%, respectively, representing increases of 31.6%, 108.9%, and 186.0%, respectively, compared with the cast 7075 alloy. This study is significant for the successful preparation of high-strength and high-toughness cast aluminum alloys with high alloying-element content. [ABSTRACT FROM AUTHOR]

It is challenging to concurrently control the microstructure evolutions after undergoing casting, sheet forming and welding. This study successfully addressed this challenge via trace TiC–TiB 2 nanoparticles in the amelioration of solidification-rolling-welding microstructural evolution. Nanoparticles refined the solidified microstructures and significantly increased the net driving force for recrystallization, promoting the precipitation of nanoscale Guinier–Preston zones and β'' phases. The coarsening of the fusion and heat-affected zones was also effectively suppressed. The yield strength (YS) and ultimate tensile strength (UTS) of the rolled plates were enhanced by 31.3% and 16.3%, respectively, without significantly sacrificing ductility. Additionally, the YS and UTS of the as-welded welding joints were enhanced by 30.2% and 7.8%, respectively. The amelioration mechanism of TiC–TiB 2 throughout the microstructural evolution and strengthening process was systematically investigated. This study provides a typical model for the complete amelioration of microstructural evolution in aluminum alloys under multiple processing conditions. • The nucleation of solidified phases is promoted, and their growth is hindered. • Recrystallization and formation of coherent nanoscale precipitates are promoted. • Coarsening of fusion zone and heat affected zone is suppressed. • Building better microstructure configuration for improved properties. [ABSTRACT FROM AUTHOR]

A new design method of Al-Si-Mg alloy manipulated by in situ nanosized crystals was proposed. Starting from source design of the microstructure manipulation agent with a high crystallographic matching relationship with the α-Al, eutectic Si and Mg 2 Si phases in Al-Si-Mg alloy, the interatomic misfit (f r) between NiTi(B2) and α-Al or Mg 2 Si is 5.0% or 5.3%, respectively, and that between NiTi(B2) and Si is 9.9%, corresponding to good crystallographic matching. Based on calculations, in situ nanosized crystals could be considered as heterogeneous nucleation sites of α-Al, eutectic Si and Mg 2 Si, thus, uniformly fine α-Al grains, near-spherical eutectic Si and fine precipitated Mg 2 Si were obtained. The solidification behavior analysis also highly corresponded to the E2EM calculations. In the alloy manipulated by 0.05 wt% NiNbTi manipulation agent, the average sizes of α-Al, eutectic Si and Mg 2 Si were greatly decreased by nearly 8, 2 and 20 times, respectively, thus achieving comprehensive multiscale manipulation of the microstructure of the alloy in one step. Specially, the huge energy stemmed from the B2 to B19' phase transformation will generate a large number of crystal defects, which provides nucleation sites and driving force for the formation of Mg 2 Si and greatly refines the Mg 2 Si.Moreover, the yield stress, tensile stress and fracture strain of the manipulated alloy were simultaneously improved by 34.1%, 20.4% and 35.0%, respectively. The excellent strength and plasticity could be ascribed to grain-refinement strengthening, Orowan strengthening and eutectic Si refinement and spheroidization, which reduced the stress concentration during deformation. The comprehensive microstructure manipulation of Al-Si-Mg alloy using nanosized crystals formed by in situ physical crystallization, especially the manipulation of the precipitated phase, is an innovative work that not only avoids the "poisoning" effect between multiple manipulation agents but also realizes comprehensive manipulation of the overall microstructure, consequently broadening further industrial applications. • The low fr shows good mismatch between Al, Si, Mg 2 Si and NiTi. • The new method achieves multiscale manipulation of the alloy in one step. • The mean sizes of α-Al, eutectic Si and Mg 2 Si were decreased by nearly 8, 2 and 20 times. • The yield strength and plasticity were simultaneously improved by 34.1% and 35.0%. [ABSTRACT FROM AUTHOR]

At high temperatures, the weakened strength and decreased ductility of Al alloys limit their industrial applications. (TiB 2 –TiC)/Al–Cu–Mg–Si composites were synthesized by adding in situ dual-phased and bimodal-sized (TiB 2 –TiC)/Al master alloys to molten Al–Cu–Mg–Si alloys. The addition of minor amounts of TiB 2 and TiC particles (0.05 and 0.1 wt%, respectively) effectively refined the α-Al grains and θ′ and Q′ precipitates and increased the elevated-temperature strength and uniform elongation of the Al–Cu–Mg–Si alloys. The 0.1 wt% (TiB 2 –TiC)/Al–Cu–Mg–Si composite showed the best yield strength (279 MPa), ultimate tensile strength (366 MPa), and uniform elongation (10.6%) at 493 K, with enhancements of 9.4%, 15.1%, and 24.7% compared to the Al–Cu–Mg–Si matrix alloy (255 MPa, 318 MPa, and 8.5%). The simultaneous increases in the elevated temperature strength and ductility of the composites were attributed to the strengthening effects of the bimodal-sized TiB 2 and TiC particles, θ′ and Q′ precipitation strengthening, and the refined partial recrystallization microstructure. [ABSTRACT FROM AUTHOR]