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The mechanical properties and microstructures of the Al-6.02 wt% Zn-1.94 wt% Mg alloy were researched by tensile test, hardness test, optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the peak aging time shortens and the tensile strength slightly enlarges with the increase of pre-stretching. Synchronously, the cleavage fracture of the pre-stretched samples from 0% to 6% was increasingly apparent, and their elongation got lower. The precipitation sequence of 4% pre-stretched alloy during aging treatment at 120 °C was supersaturated solid solution (SSS) → GPI zone → η′ phase → η (MgZn 2) phase. Rationally, the under-aged GPI zone and the over-aged η phase had smaller contribution to the intensity as against the η′ phase of the peak-aged state. The GPI zone was beneficial to elongation, which improved the fracture morphology. • The peak aging time of Al–Zn–Mg alloy shortens with increasing pre-stretching. • After the pre-deformation treatment, the tensile strength was subtly improved. • As pre-stretching increases, cleavage fractures become more evident. • For the underaged Al–Zn–Mg alloy, the strain hardening exponent decreases. [ABSTRACT FROM AUTHOR]

In this study, the changes in the microstructure, texture, and mechanical properties of the AZ31B magnesium alloy sheet after asymmetric rolling (ASR) in different shear deformations during each pass are reported. A high shear strain is induced along the sheet thickness when the velocity ratio of the upper and lower rollers is 1.8. In the case of the sheet processed via ASR in the reverse shear deformation along the rolling direction (RASR), the grain refinement, weak basal texture, and improved structural homogeneity result in better mechanical properties than those of the sheet processed via symmetric rolling (SR). However, in the case of the sheet processed via ASR in the single shear deformation along the rolling direction (UASR), shear bands containing dynamically recrystallized grains and larger numbers of dislocation are formed, tilting the peak intensity of the pole figure away from the normal direction. Moreover, the shear band with an average grain size of 5 μm causes severe structural inhomogeneity, which results in bad mechanical properties than the other two sheets. Furthermore, the twin mode changes from the double twin of the SR sheet to the extension twin of the ASR sheet under shear strain. The extension twin contributes to the optimization of the mechanical properties. Finally, the strength and elongation of the sheets processed via RASR are simultaneously improved to 250.3 MPa and 12.5%, respectively. [ABSTRACT FROM AUTHOR]

The development of lightweight multi-component alloys (MCAs) with good strength plasticity synergy faces a significant challenge, owing to the enormous number of potential component combinations, serious microstructure defects caused by poor castability, and the inefficiency of conventional empirical trial-and-error approaches. To surmount this challenge, we proposed an alloy design method, using the CALPHAD-based high-throughput calculation (HTC) to quickly identify compositions in Al(100−w-x-y-z)Mg w Zn x Cu y Si z MCAs over high-dimensional composition space that can make α-Al and Mg 2 Si nucleate at the same time. Then successfully low-cost prepared large-sized MCA ingots with less segregation and porosity, and good performance according to the HTC screening results, and the calculated nucleation temperatures were in high agreement with the experimental values, with an error ranging within 0.5%. The granular eutectic Mg 2 Si phase exhibited exceptional uniformity and dispersion within the microstructure of the Al 77 Mg 8 Zn 5 Cu 6 Si 4 alloy, with an average size of 1.8 µm. Consequently, the as-cast Al 77 Mg 8 Zn 5 Cu 6 Si 4 alloy displayed superior strength plasticity synergy at room temperature (RT), with the ultimate compressive strength reaching 706 MPa and the strain reaching 14.2%. This work demonstrates that the CALPHAD-based HTC approach provides an effective strategy for accelerating the design of lightweight MCAs with large-size and excellent mechanical properties. • Proposed an alloy design method based on high-throughput calculation (HTC). • Screened out 5 target alloys from 180 alloys by HTC. • Calculated and tested the nucleation temperature, volume fraction of the target alloys. • Discussed the formation mechanism of the eutectic structure. [ABSTRACT FROM AUTHOR]

Macro-segregation and coarse intermetallic compounds (IMCs) are common problems in lightweight multi-component alloys (MCAs), in this work, electromagnetic stirring treatment (EST) and mixed eutectic strategy were proposed to tune the solidified microstructure of Al-based MCA. For the studied MCA, the positive and negative segregation of solute elements (except for Si) were found both lower than 5 % in the ingot, and the macro-segregation was reduced by approximately 50 % after the EST utilized. Also, the dispersion of the fine eutectic β-Mg 2 Si phase was significantly promoted by applying EST, specifically, its size at the edge of the ingot was ranged in 2–4 μm. Consequently, the alloy prepared by EST present superior strength-plasticity synergy at room temperature (RT), with the ultimate compressive strength reaching 724 MPa at the edge of the ingot and the strain reaching 15.1 % at the center of the ingot. Moreover, EST was determined enhance the content of solid-solutioned Al atoms in the eutectic β-phase, thus varied its crystal structure and reduced its hardness and Young's modulus, and futher enhanced the deformation coordination between the IMCs and the matrix, thereby improving the mechanical properties of the alloy. This study elaborated the underlying mechanism of microstructural homogeneity regulation, the obtained results could offer guidance for fabricating large-sized Al-based MCAs with excellent mechanical properties. • Compositional segregation suppressed by eutectic structure and electromagnetic stirring. • Electromagnetic stirring increased solid solubility, aggravated lattice distortion, generated a diffusion sluggish effect. • Pre-precipitated Q′-phase and phase boundary distortion both promoted the precipitation of θ'-phase. • The solid solution of Al atoms in β-phase led to the decrease of hardness and Young 's modulus. [ABSTRACT FROM AUTHOR]

In this paper, "bimodal microstructure" and enhanced mechanical properties of extruded Mg-Gd-Y-Zn-Zr alloy is achieved by regulating the initial long-periodic stacking-ordered (LPSO) phases, the effect of blocky LPSO phase and lamellar LPSO phase on the dynamic recrystallization (DRX) behavior and the formation mechanism of bimodal microstructure are systematically investigated, the deformation modes, strengthening and toughening mechanism and fracture behavior of the "bimodal microstructure" are analyzed by slip traces. Blocky LPSO phase has significant particle stimulated nucleation (PSN) effect to promote DRX. The effect of lamellar LPSO phase on DRX depends on the size, fragmented lamellar LPSO with small size promotes numerous DRXed grains through the PSN effect, while continuous intragranular lamellar LPSO with large size inhibits DRX by hindering slip and grain boundary rotation, which is the key factor to form the bimodal microstructure. The almost fully DRXed H-510 sample has the lowest strength, and the H-525 sample with "bimodal microstructure" achieves enhanced comprehensive mechanical properties (ultimate tensile strength, yield strength and elongation of 383 MPa, 308 MPa and 9.2 %, respectively), which is related to the significant texture strengthening and dislocation strengthening of large-sized unDRXed grains, as well as strain coordination of higher DRXed grains fraction. The deformation mode of the DRXed regions is grain boundary sliding, while the unDRXed regions are dominated by prismatic slip, the strain incompatibility between the two is the decisive factor causing microcracks propagation and final fracture. This paper will provide theoretical guidance for the initial microstructure design of strength-plasticity synergistic Mg-Gd-Y-Zn-Zr alloys with bimodal microstructure. [ABSTRACT FROM AUTHOR]

First principles calculations based on different substitution models are performed to investigate the structural, elastic, thermodynamic, and electronic properties of body-centered cubic (bcc) Zr-Nb alloy which has great potential in biomedicine and nuclear power in the whole interval of concentration. The results show that the calculated lattice parameters decrease linearly with the increase of Nb concentration which are in good accordance with the experimental and other first principles calculations. The structure of bcc Zr is unstable at 0 K, and Nb additions can improve bcc Zr-Nb solid solution mechanical stability. Bcc Zr-Nb disordered solid solution with the relaxed structure deviate from the perfect bcc lattice position and transform into a more stable non-β phase, however, the atoms of the ordered solid solution occupy maintains the ideal sites of bcc structure. The elastic constants C ij , elastic modulus (B , G , E), Poisson's ratio and elastic anisotropy also have been calculated. When the structure of bcc Zr-Nb alloy is stable, the Nb addition can increase the elastic modulus, B/G ration and Poisson's ratio which will improve the ductility of alloy. The electronic properties have been investigated based on density of states and charge density difference. The bcc Zr-Nb alloy electronic structure is usually composed of metal bonds and covalent bonds, and metal bonds is dominated. Zr 50 Nb 50 has the highest covalent bond ratio. Finally, the thermodynamic properties are evaluated by quasi-Debye model. • The atoms of bcc Zr-Nb disordered solid solution with the relaxed structure move out the ideal bcc position. • Nb additions can improve bcc Zr-Nb solid solution mechanical stability. • The mechanical, electronic and thermodynamic properties of bcc Zr-Nb alloy in the whole concentration have been obtained. [ABSTRACT FROM AUTHOR]

The effects of silver (Ag) alloying and a retrogression re-aging heat treatment on the mechanical properties and electrical conductivity of the Al–Zn–Mg–Cu aluminum alloy were studied by means of tensile test, electrical conductivity test, and transmission electron microscopy (TEM). A trade-off between the mechanical strength and electrical conductivity was achieved, with the former reaching 558 MPa and the latter reaching 45.1 IACS. The alloy was prepared through a retrogression re-aging heat treatment (120 °C/6 h + 160 °C/7 h + 220 °C/0.5 h + 120 °C/24 h) performed on the solution and quenched samples. Furthermore, through TEM analysis of the sample solution treated at Temperature Ⅰ (420 °C/3 h + 470 °C/2 h) and Temperature II (420 °C/3 h + 480 °C/2 h), indicates that the Ag interacts with zinc or magnesium to form small clusters, which can act as precursors for η′ precipitates. η–type precipitates were the dominant precipitated phase, and the precipitation sequence was supersaturated solid solution (SSS)→ small clusters → Guinier–Preston (GP) zone → η′ → η. Furthermore, after the retrogression re-aging heat treatment, a large amount of GP (Ⅱ) and η′ precipitated in the matrix. GP (Ⅱ) and the η′ phase are related to the precipitation of {111} Al crystal plane, it is thus speculated that the interaction between the η′ phase and GP (Ⅱ) or nanosized Al 3 Zr dispersoids contributes to the strength of the alloy. Moreover, the retrogression re-aging heat treatment promotes the precipitation of the second phase, which can purify the matrix and reduce lattice distortion, thus improving the conductivity of the alloy. [ABSTRACT FROM AUTHOR]