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The overall microstructure-manipulated Al-13Si-5Cu-0.6 Mg alloy was successfully fabricated via introducing 0.1 wt% Zr 55 Cu 30 Al 10 Ni 5 amorphous alloy manipulator with short time of 60 s, to determine its suitability for applications at room and higher temperatures. The microstructure manipulation mechanism, mechanical properties and strengthening mechanism in manipulated Al-13Si-5Cu-0.6 Mg alloy were discussed. The Zr 55 Cu 30 Al 10 Ni 5 amorphous alloy manipulator provides more nucleation sites in the formation of primary Si, Al Si eutectic and Al 2 Cu. As a result, the optimal microstructure is composed of finer α-Al grains, Al 2 Cu and more rounded primary and eutectic Si, with sizes decreased to ∼52%, 13%, 73% and 42%, respectively. The yield strength, tensile strength, elongation and fracture strain of manipulated Al-13Si-5Cu-0.6 Mg alloy are improved by 22.9%, 16.8%, 58.2% and 47.7% at room temperature than those of the unmanipulated Al-13Si-5Cu-0.6 Mg alloy, respectively. The improved tensile properties at room temperature are attributed to the significant strengthening effect of smaller precipitates and grain refinement while the excellent plasticity is derived from finer α-Al grain, round-corner primary Si and eutectic Si spheroidization. The yield strength and tensile strength are increased by 28.1% and 15.3% at 250 °C, and 28.3% and 10.8% at 300 °C, respectively. The strengthening mechanism at high temperature is mainly the second phase strengthening and the effect of finer eutectic Si on the pinning grain boundary. The overall microstructure manipulation in this work provides better comprehensive mechanical properties and a practicable method to fabricate the Al-Si-Cu-Mg alloy with superior strength and ductility, especially for die-casting alloy with short-time and high-efficiency. [Display omitted] • Fully microstructure-manipulated alloy was made via adding trace nanoparticles. • Nanosized ZrCu(B2) and Zr 2 Cu have ideal lattice mismatch with Si, α-Al and Al 2 Cu. • The sizes of primary Si, α-Al, eutectic Si and Al 2 Cu decreased simultaneously. • The tensile strength and elongation of manipulated alloy are greatly improved. [ABSTRACT FROM AUTHOR]

Abstract: As-cast Mg–3Al–3Sn (AT33) alloy exhibits strong strain hardening ability, which is illustrated by the very high H c and n values. Decrease in generalized stacking fault (GSF) energies in AT33 alloys by Al and Sn additions facilitates the production of dislocations and activation of deformation twins, causing the accumulation of dislocations at twin boundaries, resulting in a high dislocation density in deformed alloys during tension deformation, which thereby mainly accounts for the strong strain hardening ability. [Copyright &y& Elsevier]

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]

Al Cu alloys inoculated by in-situ nano-sized particles crystallized from Ni-Nb-Ti amorphous alloys were prepared by casting method in this work. Different compositions of Ni-Nb-Ti amorphous alloys significantly enhanced heterogeneous nucleation for α-Al and promoted obvious grain refinement of the Al Cu alloys. It was found that 0.05 wt% Ni-Nb-Ti amorphous alloys addition caused a significant and efficient refinement on α-Al (from 200 μm to 39 μm) and θ′ phase (from 146.4 nm to 37.6 nm). The strength and ductility of the inoculated alloy were improved significantly at high temperature. The tensile strength and fracture strain of the alloy inoculated by 0.05 wt% Ni-Nb-Ti amorphous alloy for 20 min at 533 K under the strain rates of 10−1 s−1 were increased by 32.63% and 90.35% respectively, compared to those of the uninoculated alloy. The nano-sized NiTi particles contributed to the grain refinement of α-Al, and grain refinement shortened the solute atomic diffusion distance and refined θ′ phase during heat treatment, resulting in higher strength and plasticity at high temperature. The model developed for this new type Al Cu alloy is found to be efficient in predicting the stress at 453 K–533 K under the strain rates of 10−4 s−1 to 10−1 s−1. • In-situ nano-sized NiTi can serve as efficient heterogeneous nuclei of α-Al. • Inoculation caused a significant refinement on α-Al and precipitation θ′ phase. • The tensile strength and fracture strain were increased by 32.63% and 90.35% respectively at 533 K with 10−1 s−1. • The enhanced tensile property was due to the finer θ′ phase which impeded dislocation motion. • A stress prediction model was presented at 453 K–533 K under the strain rates of 10−4 s−1 to 10−1 s−1. [ABSTRACT FROM AUTHOR]