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Mechanical vibration was utilized to enhance the mechanical properties of the WAAM 2319 aluminum alloy and address issues related to coarse grains and porosity in this paper. The research aims to investigate the impact of varying vibration accelerations on the microstructure and mechanical properties of the specimens. The mechanism of solutes transfer caused by vibration has been described in this paper, which significantly improved elongation. The dendrites during growth were broken by vibration, which led to microstructure refinement. The solutes located in the interstices of the dendrites were transferred to the liquid phase by vibration, reducing the concentration of solutes in the interstices of the dendrites. The continuous coarse precipitation phase becomes intermittent and fine; resulting in increased matrix plasticity. With the increase of vibration acceleration, the elongation was significantly enhanced. The longitudinal elongation was enhanced more significantly because of the alternating distribution of INZ and ITZ, with longitudinal elongation showing a 29.3% increase and transverse elongation a 52.5% increase, while the UTS and YS was not changed significantly in the presence of multiple factors. • Mechanical vibration increases the elongation without affecting the UTS and YS. • Mechanical vibration applies reciprocating force to the dendrite, causing the fracture of the dendrite and the refinement of the grain. • Mechanical vibration induces solutes located in the dendrite interstices toliquid phase, reducing the solute concentration in the INZ. • Intermittent precipitation phases and fewer intragranular precipitation phasesin the INZ lead to increased elongation. [ABSTRACT FROM AUTHOR]

laser shock forming (LSF) is a high strain rate forming process, which can significantly improve the formability of materials. Nevertheless, there is a lack of research on the microstructure evolution and improving mechanical properties of parts deformed by LSF. In this paper, pure copper sheet are formed into flat bottom parts under one- and two-shot LSF. The deformation topography, surface morphology and thickness distribution of the deformed parts are tested. The surface micro morphology of the mould can be additionally printed in the formed parts, and the sheet forming accuracy improved continuously and lower thickness thinning with the increase of the shock number. Transmission electron microscopy (TEM) showed that the microstructure on the surface of the formed specimens was composed of nanocrystalline arrays elongated in the direction of the transverse flow of the workpiece material. The dislocation density decreased and the twinned structures gradually disappeared with an increasing depth from the treated surface. More laser shocking can refine the metal material grain and improve material mechanical property of the formed part further. Eventually, the underlying improvement mechanism of mechanical properties induced by LSF-induced microstructure evolution on pure copper was systematically revealed. • The effect of laser shock number on the morphology, thickness and microhardness of the copper was investigated. • The microstructure evolution of sheet shocked by laser with shots was characterized and the evolution model was proposed. • The strengthening mechanism of the copper part formed by two-shot laser shock was analyzed. [ABSTRACT FROM AUTHOR]

Cu/Al composites have the excellent properties of both Cu and Al, and have the properties of light weight and high conductivity, so they have been widely concerned. In this paper, 5-mm-thick Cu/Al composites prepared by the cast-rolling process are used as experimental materials. To reveal the strengthening and toughening mechanisms of the Cu/Al composites, the interfacial structure, micro-morphology, stress-strain condition, and GND distribution of Cu/Al composites before and after deformation were characterized utilizing TEM, TKD, and EBSD. The results show that the submicron intermetallic compounds Al 2 Cu and Al 4 Cu 9 are formed from the casting-rolling Cu/Al composites. After 15% tensile deformation, many gaps occurred in the interface layer, but at the gaps, there was no crack spreading to the Cu and Al layers. Meanwhile, the deformation in different directions occurs in the Cu grains near the interface, forming a dislocation wall, and the entanglement of the dislocation occurs in the Cu layer near the interface, which contributes to the improvement of tensile strength. The Al layer near the interface layer produces kink bands, which helps to improve the ductility of the composites. Besides, due to the action of the hard intermetallic compound layer, with the increase in tensile deformation, a large number of GND are gradually accumulated in the Cu and Al layers near the interface, resulting in remote back stress, which makes the softer Cu and Al layers obtain higher strength. At the same time, the back stress caused by GND will induce strain hardening, which helps to maintain ductility, so that Cu/Al composites have higher plastic deformation ability while improving mechanical properties. • The effect of the interfacial layer on the strengthening and toughening of Cu/Al composites during deformation was studied. • The Cu/Al composites could induce dislocation pile-up in the Cu side, after tensile deformation. • The deformation in different directions is generated in the Cu layer grain and the dislocation wall is formed. • GND accumulates gradually at the interface, with the progress of tensile deformation. [ABSTRACT FROM AUTHOR]

TiAl-based alloys are known for their exceptional high-temperature properties but suffer from low hot workability. The emergence of additive manufacturing (AM) technology significantly decreases the workability requirement, while the microstructure heterogeneities in AMed TiAl are troublesome. This paper explores the hot deformation behavior and microstructure evolution of a layered heterogeneous microstructure TiAl alloy prepared by selective electron beam melting. The Arrhenius constitutive model with strain compensation was established, and hot processing maps were constructed. The microstructure showed that at the initial stage of deformation, a large number of dislocation slips occur preferentially in the soft coarse-grained layers. With the increase of strain, dislocation accumulation in heterogeneous interfaces, and dynamic recrystallization (DRX) occurs. Eventually, the coarse-grained region is constantly occupied by fine DRX grains. A high density of deformation twins at high strain rates further promotes the formation of tiny DRX grains. When the hot compression temperature reaches 1200 °C, the initial alternative fine-grained and coarse-grained hetero-structure transforms into duplex (DP) and near-lamellar (NL) microstructure, and microstructure heterogeneity is eliminated. The results enhance understanding of the hot deformation behavior of heterogeneous microstructure TiAl alloys. • Constitutive equation and processing map of heterogeneous TiAl alloy are established. • Thermal plastic deformation promoted the elimination of microstructure heterogeneity. • Coarse-grained and fine-grained layer exhibit different deformation mechanisms. [ABSTRACT FROM AUTHOR]

WAAM-LDM hybrid additive manufacturing can achieve high efficiency and high precision preparation of Ti-6Al-4V alloy. However, the inhomogeneous microstructure of WAAM-LDMed Ti-6Al-4V samples results in overall poor tensile properties. Therefore, this paper attempts to ameliorate the inhomogeneous microstructure of the hybrid sample by STA, and simultaneously improve the strength and plasticity. The results showed that the WAAM zone and HAZ were composed of α colonies, the RZ and LDM zone were distributed with fine basketweave structure of the AD samples. With the introduction of STA, the microstructure of each zone of the hybrid sample changes and transformed into a 'dual-phase' structure with bi-modal α p and β t. With the increase of aging temperature, the volume fraction of β t increased and the volume fraction of α p phase decreased, accompanied by the formation of bulk α phase and the coarsening of α s phase. It is worth noting that the strength of WAAM zone was obviously improved by STA, and the fracture positions of the STA samples were randomly distributed in the WAAM and LDM zones. Additionally, with the aging temperature increased, the strength of WAAM-LDMed samples was weakened, and the ductility was improved because the coarsened bulk α played a role of coordinating deformation in the tensile process. The excellent strength and ductility (UTS = 976 MPa, YS = 876 MPa, EL = 13.57%) of WAAM-LDMed samples was achieved at aging temperature 750 °C, compared with the AD samples (UTS = 860 MPa, YS = 767 MPa, EL = 12.5%). Finally, by optimizing the STA (940 °C/1 h/WQ + 750 °C/4 h/AC), the amelioration of the microstructure and the improvement of the strength-ductility of the hybrid samples were achieved. • The microstructure of WAAM-LDM sample is homogenized into α p + β t by STA. • STA treatment makes the strength of WAAM zone comparable to that of LDM zone. • The WAAM-LDM sample prepared by STA obtain excellent strength and ductility. [ABSTRACT FROM AUTHOR]

This paper proposes a new stretch bending approach for aluminum alloy extrusion profiles based on a novel pre-hardening forming (PHF) process. Tensile tests were carried out to examine the flow behavior and mechanical responses of a 7A09 extrusion profile in PHF process. Microstructure evolution was investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and small angle X-ray scattering (SAXS). It is interesting to find that the yield stress at 200 °C was higher than that at 185 °C. The quantitative analysis revealed that the higher volume fraction of precipitates (200 °C) played a greater role than the refinement of precipitate sizes (185 °C) in precipitation strengthening mechanism, thereby causing an enhanced hardening effect. This phenomenon indicated that there was a preferred temperature zone for the precipitation behavior in PHF process, and it also explained the lower yield stress at 185 °C than that at 200 °C. Additionally, similar results were also observed in strength of the warm-deformed alloys. The optimal strength (σ / σ 0.2 =589/517 MPa) can be achieved at 200 °C without subsequent heat treatment, which exceeded the typical strength of 7A09-T6 extrusion. The primary strengthening mechanisms in PHF process were strain hardening and precipitation strengthening, and the warm forming procedure caused a hardening effect, rather than a softening impact as in traditional warm/hot forming procedures. [Display omitted] • The yield stress and warm-deformed strength initially increased and then dropped with the increasing forming temperature. • An optimal warm-deformed strength superior to typical 7A09-T6 was obtained at 200 °C without subsequent heat treatment. • The higher volume fraction played a greater role than refinement of precipitate sizes in precipitation strengthening. • The warm forming procedure caused a hardening effect, rather than a softening effect during traditional warm/hot forming. [ABSTRACT FROM AUTHOR]

In this paper, uniaxial hot compression tests of β-quenched Zr-1Nb-1Sn-0.1Fe alloy under a strain of 0.91 were conducted at various temperatures ranging from 600 °C to 750 °C. The microstructure, texture evolution, deformation mode and dynamic recrystallization (DRX) mechanism were investigated using electron backscatter diffraction (EBSD). The results of the In-Grain Misorientation Axis (IGMA) method showed that the prismatic was the dominant deformation mode when the temperature was 600 °C. The prismatic and pyramidal were the dominant deformation modes during hot compression between 650 and 750 °C. To study the mechanism of DRX, the geometrically necessary dislocation (GND) density, grain orientation spread (GOS) and grain reference orientation deviation (GROD) maps were calculated. The results showed that both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) coexisted during hot compression. When deformed at 600 °C, the recrystallization mechanism was mainly DDRX, while it was mainly CDRX above 600 °C. The change in the DRX mechanism can be attributed to the activation fraction of different slip systems and the resulting development of misorientation. • The effects of the temperatures on microstructure evolution and deformation mode were analyzed. • Different DRX mechanisms and their effects on texture are discussed in detail. • The DRX mechanism changed due to the activation of different slip systems and the resulting development of misorientation. [ABSTRACT FROM AUTHOR]

To achieve superior damage tolerance and fatigue properties, it is desirable for the microstructure of Ti-6Al-4V ELI (Extra Low Interstitial) titanium alloy to consist of equiaxed grains with a homogeneous lamellar structure. However, traditional forging and single additive manufacturing techniques require extreme processes such as quasi β heat treatment and hot isostatic pressing. In this paper, a hybrid directed energy deposition method that integrates in-situ rolling with simple annealing is proposed to simultaneously achieve these microstructures. The results indicate that the initial microstructures produced by hybrid directed energy deposition consist of fine equiaxed prior-β grains, inconspicuous interpass bright bands, randomly oriented lamellar structure and numerous small substructures at the TEM scale. Due to the plastic deformation caused by in-situ rolling, the primary β grains underwent significant refinement with a reduction in grain diameter from over 2000 μm to 113.8 μm. Besides, the unique microstructures and thickness of α laths are influenced by coarsening and dissolution mechanisms that are controlled by diffusion during phase transformation. Furthermore, a uniform microstructure without bright bands and excellent comprehensive properties can be achieved through heating at 880 °C for 2 h and natural cooling. These findings validate that hybrid directed energy deposition coupled with simple annealing present a novel and cost-effective approach for the direct manufacturing of uniform titanium alloy forgings. • Microstructure evolution in DED with in-situ rolling and annealing was studied in detail. • Uniform microstructure realized with fine equiaxed grains. • Driving forces and mechanisms of α lamellae evolution were summarized. • Optimal comprehensive properties were analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the influence of electrical pulse treatment (EPT) on the evolution of microstructure and texture and the resultant magnetic and mechanical properties of a cold rolled Nb-alloyed non-oriented silicon steel (NOSS) was investigated carefully. When the temperature rise caused by Joule heat is higher than the starting temperature of dissolution, more precipitates are dissolved in the EPT specimens than those subjected to the conventional heat treatment (CHT) at the same temperature, and higher current density resulted in Laves precipitates dissolved at lower temperature. The permeability of all the EPT and CHT specimens increase first and then decrease with the increasing temperature, and it reaches the maximum at the temperature for nearly the complete recrystallization. B 50 is higher for the EPT specimen than CHT before the completion of recrystallization due to enhanced recrystallization, but lower than CHT after the completion because the athermal effect of pulsed current promotes the growth of γ-fiber grains, disfavoring the permeability. Moreover, the EPT specimen has the lower iron loss and lower yield strength than the CHT one at the same annealing temperature, because the dissolution of precipitates, recrystallization and grain growth in cold rolled matrix are all enhanced due to the athermal effect of pulsed current. [Display omitted] • Higher current density leads to Laves precipitates in NOSS dissolved at lower temperature. • The maximum B 50 in EPT samples appeared at lower temperature than that of CHT ones. • Athermal effect of pulsed current resulted in the lower iron loss and lower yield strength. [ABSTRACT FROM AUTHOR]

In the paper, the disc sheet of 2024 aluminum alloy was shaped precisely into a flat-bottom cup by two stage laser shocking, and its microstructure evolution was studied by Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) in detail. The investigations show that the grains are elongated and continuously refined by continuous dynamic recrystallization during two stage laser shock sheet forming (TSLSSF). With the increase of strain of metal sheet, the transformation from low-angle grain boundaries and high dislocation densities to high-angle grain boundaries and low dislocation densities occurs, which improves the strength and plasticity of the processed material in comparison with the untreated material. The impact affects significantly the texture evolution process of aluminum alloy sheet under two stage forming. After laser shocking, the textures of the aluminum alloy sheet tend to be stabilized at the β-Fiber and a strong P texture is also formed. Due to the combined effect of grain size and dislocation density, the hardness of the second impact material increases less than that of the first impact. The research provides a reference for the application and development of laser shock forming. • The microstructure evolution of the material after laser shocks was characterized. • The proportion of low-angle grain boundaries first rises and then falls. • The ratio of dislocation density first enhances and then drops after laser shocks. • The textures of the sheet are inclined to be stabilized at β-Fiber and P component. • The hardness increase after the second impact is less than that after the first. [ABSTRACT FROM AUTHOR]

This paper presents the microstructure of quartz fiber reinforced SiO 2 matrix (SiO 2f /SiO 2) wave-transparent composites characterized by X-ray computed tomography (XCT) and the impregnation of silica sol by conducting permeability and pore network model analyses. Results show that in 2.5D woven structural preform silica gel mainly flowed along the extension direction of weft yarns during impregnation, and the permeability rate in this direction reached 368.49μm2. Attributing to the large pore size, large throat radius and good pore connectivity, impregnation of this preform was more uniform, resulting in a small final porosity of the composite (2.32%). Comparatively speaking, in stitched structural preform silica sol flowed primarily between the layers of fiber cloths, achieving a maximum permeability rate of 36.47μm2, but along the direction of stitching fiber yarns permeability rate was only 5.23μm2. Small throat radius and pore size of fiber preform led to poor impregnation effect and a total porosity of 11.85%. Preform structure plays a crucial role in the densification process of SiO 2f /SiO 2 composites prepared by sol-gel method. • Morphology characteristics and phase distribution of two types of SiO 2f /SiO 2 composites were observed. • Permeability and pore characteristics of fiber preforms were discussed. • Preform structure plays a crucial role in the densification process of SiO 2f /SiO 2 composites prepared by sol-gel method. • XCT has significant advantages in exploring the microstructure and anisotropy of fiber-reinforced composites. [ABSTRACT FROM AUTHOR]

In this paper, we designed a new L1 2 nanoparticles-strengthened fcc-structured (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. The high-density L1 2 nanoparticles with an average size of ∼57 nm are uniformly distributed in the grain with an average size of ∼37 μm. The volume fraction of L1 2 nanoparticles is up to ∼45%. The L1 2 nanoparticles can be identified as the (Ni,Co,Cr) 3 (Ti,Al) multi-component phase. Compared to the single-phase Co 2 Ni 2 Cr base alloy with a yield strength of ∼208 MPa and an ultimate tensile strength of ∼660 MPa, (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA possesses a much higher yield strength of ∼1125 MPa and an ultimate tensile strength of ∼1540 MPa while retaining an excellent ductility of ∼38%. The precipitation strengthening by L1 2 nanoparticles takes the largest contribution to the yield strength, and the contribution value is up to ∼712 MPa. The deformation mode is dominated by mechanical twins for Co 2 Ni 2 Cr base alloy and (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA, and the mechanical twins are more prevalent in the Co 2 Ni 2 Cr base alloy. • A new L1 2 nanoparticles-strengthened (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA is well designed. • The volume fraction of L1 2 nanoparticles with a mean size of ∼57 nm is up to ∼45%. • (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA has an excellent property (σ s ∼ 1125 MPa, σ b ∼ 1540 MPa, δ ∼ 38%). • L1 2 nanoparticles precipitation strengthening takes the largest contribution to strength. • The deformation mode is dominated by mechanical twins for (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effects of In and aging treatment on the microstructure, mechanical properties and electrochemical corrosion behavior of Sn 2Cu solder alloy. It is found that In could refine the β-Sn grains, resulting in an improved microstructure and enhanced microhardness and tensile properties. Moreover, adding In lowered the undercooling of the Sn 2Cu solder alloy, with a maximum reduction of 5.97 °C. The corrosion resistance of the alloy was also dramatically improved by In addition, as evidenced by: (1) a lower corrosion current density compared to the matrix alloy; (2) a smaller surface roughness and pit depth after corrosion; (3) an increased ratio of SnO 2 in the corrosion product layer. On the other hand, aging treatment had an adverse impact on the mechanical properties, but a beneficial influence on corrosion resistance of solder alloy. • In and aging treatment effectively changed the mechanical and electrochemical properties of Sn 2Cu solder alloys. • In significantly increased the ratio of SnO 2 in the corrosion product layer of solder alloys • In dramatically reduced the undercooling and pasty range temperature range of Sn-2Cu solder alloys [ABSTRACT FROM AUTHOR]

In this paper, the NbTa 0.5 TiZr X series refractory high entropy alloys(RHEAs) were processed by selective laser melting (SLM). NbTa 0.5 TiZr X alloy are observed with BCC crystal structures.The effect of Zr content on microstructure and properties of NbTa 0.5 TiZr X alloys was studied, as the Zr content increases, the main defects of NbTa 0.5 TiZr X alloy changed from lack of fusion defects to solidification cracks. Due to the different melting points of alloying elements, the elements with high melting point are enriched in the dendrite and the elements with low melting point are enriched in the inter-dendrite. As the Zr content increases, the number of cellular subgrain increases, and the number of columnar subgrain decreases. The fine equiaxed grain at the boundary of the molten pool and the coarse grain in the molten pool make the grain of the NbTa 0.5 TiZr X alloy with bimodal size distribution. The compressive yield strength increases with the increase of Zr content. Due to the effects of solid solution strengthening, precipitation strengthening and fine crystal strengthening, the alloy has the highest yield strength of 1320 MPa. When Zr content reaches 10 wt%, and the Compressive strain of NbTa 0.5 TiZr X alloy exceeds 75% at room temperature. • We designed and prepared a NbTa 0.5 TiZr X RHEA. • The novel alloy shows high ductility at RT. • compressive strength increased with increasing Zr content. • The NbTa 0.5 TiZrx alloy was fabricated by SLM using elemental mixed powders. [ABSTRACT FROM AUTHOR]

In this paper, the rolled TiB whisker (TiBw)/Ti65 composites with different rolling reductions were obtained by high temperature (HT) rolling in the β single-phase region. The changes in TiBw, silicide and grain size after rolling deformation were analyzed by microstructure characterization. Based on this, the strengthening mechanism and HT deformation behavior of rolled composites were analyzed in combination with room temperature and HT tensile experiments. The results show that TiBw fractured after rolling deformation, leading to a decrease in the aspect ratio and an increase in matrix connectivity. Silicide with an average diameter of 80 nm appeared in the rolled composites. The grain was continuously refined as the rolling reduction increased. A T-type texture with the crystal C-axis parallel to the transverse direction appeared at 40% rolling reduction. The strength and plasticity of sintered TiBw/Ti65 composites were increased after rolling. With an increase of rolling reduction, the composites exhibited fine-grain strengthening below 650 °C. When tensile above 700 °C, a softening effect occurred with the decrease of grain size, that is, the yield strength decreased for grain size <3.6 μm. The strengthening mechanisms of rolled TiBw/Ti65 composites include fine grain strengthening, load transfer strengthening of TiBw, Orowan strengthening of silicide, and dislocation density strengthening. Among them, fine grain strengthening and load transfer strengthening predominated and increased as the rolling reduction increased. After tensile at 750 °C, many recrystallized grains with large misorientation appeared around the initial coarse grains and TiBw. • The strength and plasticity of sintered TiBw/Ti65 composites were increased by HT rolling. • The effects of rolling reductions on microstructure and mechanical properties were studied. • The strengthening mechanism of rolled TiBw/Ti65 composites was analyzed. • The effect mechanisms of silicide on mechanical properties and DRX were investigated. [ABSTRACT FROM AUTHOR]

The formation of interfacial intermetallic compounds (IMCs) such as Cu 6 Sn 5 , Cu 3 Sn or platelet-shaped Ag 3 Sn which are formed in reflow soldering process will directly destroy the soldering reliability. Magnetic pulse welding (MPW), as a solid state welding technique can effectively restrain or even impede the formation of interfacial IMCs. In this paper, Cu and Sn dissimilar metals were welded by MPW under the discharge energy from 17 to 31 kJ. The typical wavy interface and metal jet flow were found in all samples. When the discharge energy reached 31 kJ, a typical gradient nanograined (GNG) interface has been observed to undergo an evolution from a sub-micron secondary solid solution of Cu 6.26 Sn 5 IMCs to a nanoscale secondary solid solution of Cu 81 Sn 22 IMCs, followed by the formation of nanoscale equiaxed α-Cu grains, and ultimately leading to the deformed elongated nanoscale α-Cu grains. This discontinuous distribution of the aforementioned phases occurs specifically at the interface of the 23 kJ_1.5 mm sample. In contrast, when subjected to a discharge energy of 17 kJ, there were no indications of a secondary solid solution of Cu 6.26 Sn 5 IMCs or elongated nanoscale α-Cu grains. However, a discontinuous secondary solid solution of Cu 81 Sn 22 IMCs was observed to form at the Cu/Sn interface under these conditions. Based on these findings, the utilization of microprojection welding (MPW) techniques involving Cu and Sn-based solder in the microscale is anticipated to serve as a highly efficient and automated technology within the field of electronic micropackaging. [Display omitted] • The wavy interface and metal jet were formed at the Cu/Sn interface. • The gradient nanograined interface has been observed. [ABSTRACT FROM AUTHOR]

In this paper, in-situ nanoparticles ZrB 2 were introduced to improve the mechanical properties of Friction Stir Welding (FSW) joints in 7N01 matrix composites. The recrystallization driving force was increased induced by ZrB 2 particles. Modified by ZrB 2 nanoparticles, the grains in the SZ (stir zone) were refined from 4.8 μm (7N01) to 3.7 μm (ZrB 2 /7N01), and the recrystallization proportion was increased from 75.1% (7N01) to 85.4% (ZrB 2 /7N01). Compared with the 7N01 matrix, the ultimate tensile strength (UTS) of friction stir welding joints in ZrB 2 /7N01 composites was enhanced from 283.3 to 395.6 MPa, the yield strength (YS) was enhanced from 250.8 to 361.4 MPa, elongation was enhanced from 12.7% to 16.2%. The strengthening effect was mainly achieved through the Orowan mechanism. The MgZn 2 precipitates grew up under the influence of heat input, the inhibiting effect of precipitates on dislocations movement was weakened. Nanosized ZrB 2 particles with superior coarsening resistance can still maintain its morphology and size at high temperature, playing a good strengthening role during the FSW. • High temperature stable phase ZrB 2 particles can still play a good strengthening role during the FSW welding. • ZrB 2 particles can promote and hinder recrystalization, which driving force was larger than restraining force. • The semi-coherent interface between ZrB 2 and α-Al promote precipitation of MgZn 2. [ABSTRACT FROM AUTHOR]

A novel LPSO containing Mg-5Y-2n-2Li-0.5Al alloy with superior mechanical behaviors and damping capacities was first developed in this paper. The microstructure evolution, mechanical and damping properties of Mg-5Y-2n-2Li-0.5Al alloy were analyzed and compared with those of Mg-5Y-2Zn-2Li alloy. The results indicated the extruded Mg-5Y-2n-2Li-0.5Al alloy exhibited bimodal grain structure, including fine dynamically recrystallized grains (DRXed grains) and coarse un-dynamically recrystallized (unDRXed) grains, accompanied by the produce of the 14H LPSO phase, Al 3 (Y, Zn) particle and nano-precipitates AlLi phase. Due to the strengthening effects of grain boundary, residual dislocation and precipitation, the ultimate tensile strength (UTS), tension yield strength (TYS) and elongation (EL) of the extruded Mg-5Y-2Zn-2Li-0.5Al alloy were 312 MPa, 229 MPa and 10.9%, respectively, which were higher than that those of the extruded Mg-5Y-2Zn-2Li alloy. In addition, the extruded Mg-5Y-2Zn-2Li-0.5Al alloy displayed good damping capacities at both room and high temperature (RT and HT), and its RT damping value (Q−1) at 5 × 10−4 strain amplitude exceeded 0.01, which associated with a high density of movable dislocation. With rising the temperature, the extruded Mg-5Y-2n-2Li-0.5Al alloy possessed superior damping properties than the Al-free alloy, which derived from the grain boundary slide (GBS) and the activation of the incoherent interface between the Al 3 (Y, Zn) and α-Mg phase after adding Al element. [Display omitted] • The addition of trace Al element significantly changed the microstructure of the Mg-5Y-2Zn-2Li alloy. • The mechanical properties and damping capacities were simultaneously improved in the extruded Mg-5Y-2n-2Li-0.5Al alloy. • It was a major breakthrough in balancing the relationship between strength and damping of Mg alloys. [ABSTRACT FROM AUTHOR]