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The effects of Sn content on strain hardening behavior of as-extruded Mg-xSn (x = 1.3, 2.4, 3.6 and 4.7 wt%) binary alloys were investigated by uniaxial tensile tests at room temperature. Strain hardening rate, strain hardening exponent and hardening capacity were obtained from the true plastic stress-strain curves. After hot extrusion, the as-extruded Mg-Sn alloys are mainly composed of α-Mg matrix and second phase Mg 2 Sn, which only exists in Mg-3Sn and Mg-4Sn. Average grain size decreases from 15.6 μm to 3.6 µm with Sn content increases from 1.3 to 4.7 wt%. The experimental results show that Sn content decreases strain hardening ability of as-extruded Mg-Sn alloys, but gives rise to an obvious elevation in tensile strength, yield strength and elongation of them. With increasing Sn content, strain hardening rate decreases from 3527 MPa to 1211 MPa at ( σ - σ 0.2 ) = 50 MPa, strain hardening exponent decreases from 0.21 to 0.13 and hardening capacity decreases from 1.66 to 0.63. The variation in strain hardening behavior of Mg-Sn alloys with Sn content is discussed in terms of the influences of grain size and distribution of grain orientation. [ABSTRACT FROM AUTHOR]

An in-depth study of the anisotropic mechanical behavior of Mg alloys is essential for optimizing mechanical properties, designing high-performance Mg alloys, and developing processing processes. This work investigates the microstructure and mechanical anisotropy of Mg–6Zn-xY-0.5Ce-0.4Zr (MZCZ-xY) alloys with varying Y contents subjected to asynchronous rolling (ASR). The Y content significantly affects the microstructure and mechanical anisotropy of the MZCZ-xY alloy. In lower Y content alloys (MZCZ-0.2Y, MZCZ-0.5Y), the second phase mainly consists of Mg 3 Zn 6 Y (I phase) and Mg 1.5 Zn 9.5 Ce 3 , while the addition of 1.0 wt% Y leads to the appearance of Mg 3 Zn 3 Y 2 (W phase) in the alloy. Furthermore, increasing Y content results in grain growth in the as-cast state, which will affect the average grain size after asymmetric rolling (ASR) deformation. However, alloys with higher Y content exhibit a more pronounced effect of grain refinement at the same ASR strain. Moreover, increasing Y content promotes the activation of tensile twins, with higher Y content leading to greater tensile twin activation after ASR treatment. The MZCZ-0.2Y alloy shows lower mechanical anisotropy, which is closely related to the homogeneous texture component and uniform Schmid factor (SF) in each loading direction. Therefore, the regulation of mechanical anisotropy in Mg alloys can be achieved by obtaining uniform texture components and uniform SF in each loading direction. [ABSTRACT FROM AUTHOR]

In this work, Ti P /VW94 composites were prepared by semi-solid stirring assisted ultrasonic vibration followed by hot extrusion. The results indicate that the presence of Ti particles can promote the precipitation of lamellar long period stacking ordered structure (LPSO) while inhibiting the precipitation of block-shaped LPSO during heat treatment due to the dislocations introduced by Ti particles. Besides, the content and size of RE-rich phase decrease with the increase of the Ti particle content. The lamellar LPSO can hinder recrystallization and RE-rich phase can hinder grain growth. The addition of Ti particles decreased the grain size, recrystallization fraction and texture intensity of as-extruded Ti P /VW94 composites compared with VW94 matrix alloy. The 5%Ti P /VW94 composite presents the best tensile properties, with a YS, UTS and elongation of 288 MPa, 371 MPa and 9.4%, respectively. The enhanced tensile properties of Ti P /VW94 composites are attributed to the load transfer, grain refinement, dislocation strengthening, dispersion strengthening, and an increase in lamellar LPSO and RE-rich phase with appropriate content and size. [ABSTRACT FROM AUTHOR]

The microstructure, dynamic recrystallization, texture, anisotropic behaviour, mechanical properties and electromagnetic shielding effectiveness of Mg–Zn–Zr–Ce alloys were comprehensively investigated in this study. Results indicated that the addition of Ce refined the grains and induced the formation of a Mg–Zn–Ce phase with a unique orthorhombic structure. Dynamic recrystallization was improved when Ce was added because the particle stimulated nucleation mechanism. The random orientation of recrystallization grains weakened the basal texture. The anisotropy index decreased from 1.02 to 0.43 after 1.16 wt% Ce was added. Ce addition enhanced the mechanical properties when the Ce content ranged from 0 to 1.90 wt%, and then decreased with a higher 2.74 wt% Ce content. Electromagnetic shielding effectiveness was also improved initially with the addition of Ce, and then decreased, but was still higher compared with the Ce-free alloy. Good mechanical properties and excellent electromagnetic shielding properties were simultaneously achieved through 1.16 wt% Ce addition. The alloy not only exhibited good yield strength (249 MPa), ultimate tensile strength (316 MPa), and elongation (δ=15%) but also superior electromagnetic shielding effectiveness with 71 dB at 1200 MHz. [ABSTRACT FROM AUTHOR]

In the field of magnesium matrix composites (MMCs), it is vital to improve the strength of MMCs without sacrificing plasticity. In this work, Ti P /VW94 composites with different Ti particle sizes were prepared by semi-solid stirring assisted ultrasonic vibration method and then subjected to homogenizing treatment. The microstructure results show that the Ti particles are conducive to forming the RE-rich phase. The Mn atoms diffused to the edge of Ti particles, and a submicron layer of MnTi formed at Mg/Ti interface. The atomic spacing misfit at the Mg/MnTi interface is 2.8%, indicating that a strong interfacial bonding was formed at the Mg/Ti interface. The tensile test results show that the strength and elongation all improved after adding Ti particles and improved first and then declined with the decrease of fine Ti particles and the increase of coarse Ti particles. The YS of D3 sample with 2.5% fine Ti particles and 1% coarse Ti particles increased by 12%, the UTS increased by 21%, and the elongation increased by 48% compared with the VW94 matrix alloy. [ABSTRACT FROM AUTHOR]

The effects of trace Y and Ce additions on the microstructure and mechanical properties of extruded Mg–Zn–Zr alloy sheets were investigated. Results indicated that Y and Ce additions led to significant grain refinement and to the formation of Mg–Zn–Ce, Mg 3 Zn 6 Y (I-phase) and Mg 3 Zn 3 Y 2 (W-phase). Mg–Zn–Ce and W-phase were found to possess an orthorhombic and a face centered cubic structure, respectively. Ultimate tensile strength, particularly yield strength, significantly increased after Y and Ce additions, and good elongation was also achieved. The extruded alloy with 0.28 wt% Y and 0.52 wt% Ce exhibited optimal yield strength (313 MPa), ultimate tensile strength (356 MPa) and elongation (12.1%). With increasing Y and Ce additions, strain hardening rate decreased, and the yield-to-ultimate tensile strength ratio ( σ s /σ b ) increased. Variations in mechanical properties were discussed based on microstructure observation. [ABSTRACT FROM AUTHOR]

In our previous work, we designed a new as-cast Mg–Y–Zn–Al–Li alloy with a high elastic modulus of 52.9 GPa. The alloy was further subjected to hot deformation under different rolling reductions (40% and 80%) in this work. The microstructure evolution, texture and mechanical properties of Mg–Y–Zn–Al–Li alloy compared with Mg–Y–Zn alloy were systematically investigated. The result showed that the Mg–Y–Zn–Al–Li alloy with a rolling reduction of 40% displayed a more homogeneous fine microstructure and a weakened basal texture, accompanied by the formation of Al–Li and nano-precipitates Al 0.9 Li 34.3 Mg 64.5 Zn 0.3 phase. Compared with the Mg–Y–Zn alloy, the strength and ductility of the alloy also were obviously enhanced while possessing a weak mechanical anisotropy. Grain refinement and second phase strengthening (fine Al–Li phase and nano-precipitates Al 0.9 Li 34.3 Mg 64.5 Zn 0.3) mainly contributed to the enhanced strength. The texture weakening, low dislocation density and non-basal slip commonly guaranteed the high ductility, especially the weakened texture gave rise to the low anisotropy. When the rolling reduction increased to 80%, the volume fraction of recrystallized grains in Mg–Y–Zn–Al–Li alloy increased significantly to73.3%. As a result, the symmetry of the texture distribution around the ND was appreciably improved. In addition, the lower dislocation density and more non-basal slip in the Mg–Y–Zn–Al–Li alloy with the rolling reduction of 80% further enhanced the ductility. Simultaneously, the anisotropic degree of mechanical was effectively minimized, which was mainly attributed to the weak symmetric texture caused by fine DRXed grains with random misorientation and non-basal pyramidal slip. [ABSTRACT FROM AUTHOR]

In the field of lightweight metals, it is difficult to develop magnesium (Mg) alloys with both high-modulus and high-strength. In this paper, the results show that adding Ge element to the base Mg-Gd-Ag-Mn alloy can simultaneously improve the elastic modulus and strength of the alloy, and the higher the Ge content is, the higher the modulus and strength will be. After Ge alloying, the average grain size and texture of Mg-Gd-Ag-Mn-Ge alloy are reduced and new high-modulus MgAg and Gd 5 Ge 3 phases are formed compared with the base Mg-Gd-Ag-Mn alloy. In Ge-containing alloys, the Mg-10Gd-1.5Ag-0.2Mn-3.5Ge alloy obtained the best comprehensive mechanical properties, the elastic modulus, strength and ductility are 51 GPa, 423 MPa and 10%, respectively. The high-modulus is due to the formation of high-modulus second phases. The high-strength is the result of dislocation strengthening, grain boundary strengthening and precipitation strengthening. [ABSTRACT FROM AUTHOR]

The novel cast Mg-1.3Y-0.8Zn-6.4Al-16.7Li (at. %) alloy showed excellent comprehensive properties including high elastic modulus of 52.9 GPa, ultra-high specific modulus (E / ρ) of 33.1 GPa cm3/g and superior damping capacity. The high elastic modulus was attributed to Li in solid solute and the formation of high modulus Al–Li compounds and Al 2 Y particles, and the simultaneous decrease in density due to Li addition results in the ultra-high specific modulus. At room temperature, the excellent damping capacity in the alloy was due to the presence of a large number of movable parallel dislocations. Moreover, the alloy could be classified as the high damping metal (Q − 1 > 0.01) in the strain amplitude region. With the increasing temperature, the superior damping capacity of the alloy could be explained by dislocations movement and grain boundary gliding. [ABSTRACT FROM AUTHOR]

Gradient Mg-6Zn-0.2Y-0.4Ce-0.5Zr alloy sheet, with a nanocrystalline surface layer of 98 nm on the topmost surface, was prepared by sliding friction treatment (SFT). Nanoindentation test used to research the influence of grain refinement on the creep behavior and corresponding deformation behaviors under different range of loading strain rates. It is shown that nano-grained layer exhibits a long creep distance but a peaceful creep behavior, which is mainly attributed to the abundant plastic deformation behaviors after nanocrystallization. The corrosion behavior of SFTed layer and un-SFTed layer was investigated by electrochemical tests and hydrogen evolution in 3.5% solution. The corrosion resistance is improved in the nano-grained layer by the reduction of grain size which promotes the formation of passive film and the rearrangement of second-phase particles which suppresses the corrosion rate. SFT method is an effective way in refining grain size while improving the corrosion resistance. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization, texture evolution and mechanical anisotropy of rolled AZ31 alloys with varying impurity content were systematically investigated in the present work. The results suggested that, after rolling reduction of 20% and 50%, reducing impurity content led to an increase in the volume fraction of dynamic recrystallized (DRXed) grains. For the AZ31 alloys with rolling reduction of 50%, the texture was weakened and the mechanical anisotropy was improved with decreasing impurity content. The ultimate tensile strength anisotropy (UA), yield strength anisotropy (YA) and elongation anisotropy (EA) decreased significantly from 21.4%, 48.1% and 91.3% to 5.2%, 14.3% and 42.2%, respectively. The planar anisotropy Δ r also decreased from 0.0969 to 0.0523. The improved anisotropy was attributed to the weakened basal texture, fine grain size and homogeneous microstructure caused by accelerated DRX process. [ABSTRACT FROM AUTHOR]

The precipitation phase was tailored by adding different Sn contents to the Mg-12Gd-3Y alloy to achieve multiphase composite strengthening. Adding different Sn contents has different effects on the microstructure and mechanical properties. Adding 1.0 wt% Sn to the Mg-12Gd-3Y alloy produced Mg 5 RE, Sn 3 RE 5 , and β′ precipitates, which were uniformly diffusely distributed within the alloy. When Sn elements were added up to 1.5 wt%, Mg 5 RE and Sn 3 RE 5 precipitates increased and aggregated into lumps. The prepared Mg-12Gd-3Y-1.0Sn alloy exhibited excellent room and elevated temperature (ET) mechanical properties. The ultimate tensile strengths (UTS) of Mg-12Gd-3Y-1.0Sn alloy after extrusion and aging (E-A) treatment were 476, 415, 383 MPa at RT, 200 °C, and 250 °C, respectively. The fine grain size inhibits dislocation sliding, and the uniformly diffuse multi-scale phase structure inhibits the expansion of grain boundary cracks, resulting in excellent strength of Mg-12Gd-3Y-1.0Sn at room temperature (RT). The excellent ET strength of the Mg-12Gd-3Y-1.0Sn alloy is derived from the homogeneous diffusion of multi-scale heat-resistant precipitates within the alloy. • Sn can be combined with RE elements to form superior heat-resistant precipitates. • MGY-1.0Sn alloy has the best RT and ET strength. • Excellent ET strength results from the homogeneous distribution of multi-scale heat-resistant precipitates. [ABSTRACT FROM AUTHOR]

There is a tremendous demand for heat-resistant Mg alloys in aerospace and automotive applications. In this paper, different Nd contents are added to Mg-12Gd-3Y alloy to design the joint action of multiple rare earth (RE) elements to improve the elevated-temperature (ET) strength. The Mg-12Gd-3Y-1.0Nd alloy after extrusion and aging (E-A) process showed excellent strength and toughness matching at room temperature (RT), 200 °C, and 250 °C. The E-Aed Mg-12Gd-3Y-1.0Nd alloy showed ultimate tensile strength (UTS), tensile yield strength (TYS), and elongation (EL) of 440 MPa, 312 MPa, and 6.2% at RT. The E-Aed Mg-12Gd-3Y-1.0Nd alloy showed UTS, TYS, and EL of 405 MPa, 306 MPa, and 12.6% at 200 °C. The E-Aed Mg-12Gd-3Y-1.0Nd alloy showed UTS, TYS, and EL of 382 MPa, 303 MPa, and 19.4% at 250 °C. The addition of Nd elements reduces the solid solubility of Gd, and Y in the Mg matrix, thus precipitating many Mg 5 RE and β′ phases in the alloy. The excellent mechanical properties of Mg-12Gd-3Y-1.0Nd alloy after E-A treatment come from the fine grain size, segregation at grain boundaries (GBs), and delicate dispersed second phases. The fine grain size is beneficial to inhibit crack expansion, allowing it to consume more energy during the expansion process and improve strength. Both grain boundary segregation and diffusely distributed second phase can effectively inhibit grain boundary sliding and enhance strength. • Nd reduces the solid solubility of Gd and Y, thus precipitating more secondary phases. • The Mg-12Gd-3Y-1.0Nd alloy exhibits excellent strength and toughness matching. • The excellent mechanical properties come from the synergistic effect of multiple strengthening mechanisms. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of as-extruded and as-aged Mg–4Zn–1.5Al (in wt%) alloy rods were investigated systematically. The results indicate that the addition of Sn to as-extruded Mg–4Zn–1.5Al alloys can lead to the formation of Mg 2 Sn and refine the grain size as the Sn content is less than 2%. However, higher Sn results in the coarsening of grain and secondary precipitates. Among the as-extruded alloys, Mg–4Zn–1.5Al–2Sn alloy exhibits optimal combination of strength and ductility, the ultimate tensile strength (UTS), yield strength (YS) and elongation ( ε f ) are 305 MPa, 195 MPa and 15%, respectively. A subsequent T5 heat treatment was carried out on as-extruded Mg–4Zn–1.5Al–2Sn. After aging at 150 °C for 5–50 h, there are much more secondary precipitates, which results in improved strength and ductility. The best combination of strength and ductility is as-extruded ZAT422 alloy aging at 150 °C for 40 h, the UTS, YS and ɛ f are 314 MPa, 236 MPa and 18%, respectively. [ABSTRACT FROM AUTHOR]

The Mg-based composites have been considered as an efficacious method to enhance the strength of Mg matrix. How to concurrently augment the strength and ductility of the Mg matrix composites remains a pivotal concern. In this work, Mg-6Zn-1Mn (ZM61) composites, reinforced with varying contents of deformable Ti particles, were successfully manufactured employing a method of semi-solid stirring coupled with ultrasonic treatment, subsequently followed by hot extrusion. The outcomes demonstrated marked enhancement in strength and ductility of composites. The interfacial reaction between Ti and Mg matrix minimized the precipitation of MgZn 2 and α-Mn in the matrix. Ti particles boosted the dynamic recrystallization (DRX) behavior effectively. The TEM characterizations revealed that MgZn 2 nucleated on the Ti particle and Mn diffusion layer was formed in the Ti particle. The 2Ti/ZM61 composite achieved superior comprehensive mechanical properties, marked by the YS of 288 MPa, the UTS of 383 MPa, and the elongation to 22.1 %. The augmented strength was primarily owning to the grain boundary strengthening and the mismatch coefficient of thermal expansion (CTE) between Ti and Mg. The synergistic deformation of Ti particles was the main reason of improving the ductility. [ABSTRACT FROM AUTHOR]

A series of Mg-RE composites were fabricated through the sintering process involving a Mg-Gd-Zn-Zr alloy and externally introduced TC4 particle powder, follow-up subsequent hot extrusion. The addition of TC4 manifested a discernible influence on the weakening of the texture and refinement of the grain size. The TC4/GZ151K composite evinced an excellent mechanical property with 305 MPa, 361 MPa, and 10.5 % for yield strength, ultimate tensile strength, and elongation. Microstructural characterization shows that the activation of {10–12} twinning has been restrained in TC4/GZ151K composite undergoing tension, leading to a later strain-hardening rate and higher yield strength. The prominent yield plateau and the extended work-hardening stage of the TC4/GZ151K composite can be attributed to dislocation multiplication, e.g., basal slip and prismatic slip, and the interaction between the mobile dislocations and the TC4 reinforcements. The misorientation distribution analysis demonstrated that deformable Ti metal particles exhibit co-deformation with the matrix, positively influencing the plasticity of the composite. This study extended the feasibility of fabricating Mg-RE composites reinforced with deformable metal particles, providing a deeper exploration for achieving the strength-ductility trade-off for Mg composites. [ABSTRACT FROM AUTHOR]

This study analyzed the microstructure and mechanical properties of a dual-phase Mg–Li alloy produced through submerged friction stir processing. The study focused on the recrystallization and grain refinement of distinct α-Mg and β-Li phases. Two methods were identified for refining the grains. The first method involved dynamic recrystallization in large deformed grains, resulting in recrystallized grains that had minimal impact on the two-phase distribution. The second method utilized a phase transition for the growth of new α-Mg and β-Li grains occurred through heterogeneous nucleation in the other phase. The relationship between the α-Mg and β-Li phases after the phase transition was observed to have an orientation of Mg[11–20]//Li[100], Mg(0–110)//Li(011). Maelstrom-affected zones were carefully observed near the advancing side, where severe recrystallization, phase transition, and second phase refinement occurred in this region. Submerged friction stir processing prevented grain growth due to a high density of phase boundaries and rapid heat dissipation. As a result, micro-nano grains were observed in the maelstrom-affected zone. The ductility of the interface was enhanced by the maelstrom-affected zone. Therefore, the maelstrom flow can improve mechanical performance through grain refinement and redistribution for dual-phase Mg–Li alloys during submerged friction stir processing. [ABSTRACT FROM AUTHOR]

The precipitation behavior of TC4/GZ151K composite (Ti–6Al–4V reinforced Mg-15Gd-1Zn-0.4Zr) after solution and aging heat treatment (T6-treated) has been investigated. Quantitative measurements of precipitates revealed that nano-β′ phase in T6-treated TC4/GZ151K composite was denser and thinner than that in T6-treated GZ151K matrix, generating higher ultimate tensile strength of composite than that of matrix (410 MPa vs. 373 MPa). it was disclosed by geometric phase analysis that there were more geometrically necessary dislocations in solution-treated composite than that in the matrix, which was caused by different coefficient of thermal expansion between TC4 and Mg. High-density dislocations are beneficial to precipitate fine and dense β′ phase in the composite while low-density dislocations result in coarse and loose β′ phase in the matrix after aging process. This work confirmed the accelerating effect of TC4 particles on Mg-matrix's aging precipitation, which was of great significance to regulate the precipitation behavior of Mg alloy and produce high strength-ductile Mg materials. [ABSTRACT FROM AUTHOR]

Asymmetric extrusion (AE) is frequently used to weaken the texture of magnesium (Mg) alloys to improve their mechanical properties. In this paper, to explore the influence of asymmetric extrusion on the microstructure and mechanical properties of Mg matrix composites (MMCs), we synthesized TC4/AZ31 composite sheets via ball milling coupled with sintering and then various extrusions (including conventional extrusion (CE), transverse-directional AE (TDE), and normal-directional AE (NDE)). The differences in microstructure and performance among the three processed samples were compared and analyzed using SEM, XRD, EBSD characterization and tensile testing. The results showed that the asymmetrically extruded samples achieved better mechanical properties compared to their CE counterparts. It found that the grain refinement was relatively significant and texture evolution was dispersed in AE samples compared to the CE ones, which was attributed to the TC4 particle (TC4 p ) disturbance and extra asymmetric shear of matrix flow. Three different macro-textures were obtained in various extruded processes, and the micro-texture of each sample changed in diverse regions. Based on grain orientation spread (GOS) analysis, the introduction of TC4 p resulted in dynamic recrystallization (DRX) and particle-stimulated nucleation (PSN) effects during the AE process at 350 °C. The mechanisms of the combination of ductility and strength in the AE-processed sheets were related to the finer grains, high Schmid factor (SF), evenly distributed dislocations and scattered texture. This work can also provide the feasibility and prospects of applying asymmetric extrusion to MMCs. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) matrix composites are recognized as the most promising light structural materials and have been extensively investigated, but they still suffer from a relatively low ductile nature which seriously affects their further development. Herein, the Mg–9Al–1Zn (AZ91) Mg matrix composites with different sizes of Ti particles reinforcement can be obtained via hot pressed sintering followed by hot extrusion. The microstructure demonstrated that the interfacial region is consisted of Mg 17 Al 12 and Al-rich phase. Uniaxial tensile experiments revealed that the AZ91-Ti (particle size of 15 μm) composite achieves the optimal comprehensive mechanical properties, and the corresponding yield strength (YS), ultimate tensile strength (UTS), elongation (EL) of the composite can reach the high values of 210 MPa, 310 MPa, 15.5%, respectively. Moreover, with the decrease of Ti particle size, grain refinement and the strong interfacial bonding between Ti particles and Mg matrix render as-prepared the composites exhibited outstanding mechanical properties. Ti reinforcement particles of appropriate size can alleviate the plastic strain accumulation during the tensile and compressive cyclic loading, so that the excellent ductility of the composite is obtained. Constitutive relation of AZ91-Ti composites in this experiment can be derived from the nonlinear elastic relation. The simulated stress-strain curves of the composites reinforced by Ti particles with different sizes are consistent with the experiment. • The AZ91-Ti (15 μm) composite represents a noteworthy improvement in UTS, EL and elastic modulus. • Ti reinforcement particles of appropriate size can alleviate the plastic strain accumulation during the cyclic loading. • The stress-strain behavior of composites can be described by the nonlinear elastic constitutive relation. [ABSTRACT FROM AUTHOR]

Obtaining a highly synergistic strength and elongation in cast magnesium (Mg) alloys at low cost is a chronic problem. A series of low-cost and high strength cast Mg–7Zn- x Al-0.3Mn (x = 1, 3, 5) alloys (labeled as ZAM710, ZAM730, and ZAM750 alloys, respectively) were designed based on the phase diagram simulation and prepared successfully by electric resistance furnace. The present results showed that the as-cast ZAM710 alloy was composed of α-Mg, MgZn, AlMn, and Al 8 Mn 5 phases. The MgZn phase disappeared and the Mg 32 (Al, Zn) 49 phase formed as the Al content increased to more than 3 wt%. In addition, with the increase of Al content, the volume fraction of the second phase increased and the grain was refined. The microstructures and mechanical properties of these alloys were improved after heat treatment. Among them, the transmission electron microscopy analysis showed that there were a large number of nanometer precipitation strengthening phases in the aged ZAM750 alloy. One was a rod-shaped Mg 4 Zn 7 phase and the other was a disk-shaped MgZn 2 phase. The comprehensive mechanical properties of the ZAM750 alloy were most outstanding, and the tensile strength, yield strength, and elongation were 309.4 MPa, 202.0 MPa, and 6.1%, respectively. The strengthening mechanism of the ZAM750 alloy mainly included grain boundary strengthening and precipitation strengthening, and the contribution values to the yield strength of the ZAM750 alloy were 95.8 MPa and 75.7 MPa, respectively. This work can provide some guidance and new design ideas for the development of low-cost and high-strength cast Mg alloys. [ABSTRACT FROM AUTHOR]

High-performance as-extruded and peak-aged Mg-9.2Gd-3.3Y-1.2Zn-0.9Mn (wt%) alloys have been fabricated by semi-continuous casting, heat-treating, extruding and ageing processes. The effects of different heat treatments on the microstructure and mechanical properties have been investigated. Lamellar and bulk-shaped 14H-type long-period stacking ordered (LPSO) phase and few RE-rich (RE: rare earth element) particles form by different heat treatments. After hot extrusion, the heat-treated alloy with bulk-shaped LPSO phase exhibits an equal-axial microstructure, while the heat-treated alloy with lamellar LPSO phase across the grains shows bimodal grain microstructure consisting of fine equal-axial grains and coarse deformed grains. The more profuse lamellar LPSO phase in heat-treated alloy generates higher volume fraction of deformed grains and finer equal-axial grains, hence leads to higher strength but lower ductility. After ageing, the alloy with profuse LPSO and β′ phases achieves the superior mechanical properties with ultimate tensile strength (UTS) of 525 MPa, tensile yield strength (TYS) of 420 MPa and elongation to failure (EL) of 6.3%. The alloy strengthening is mainly attributed to the bimodal grain microstructure, LPSO phase, Mg 5 Gd (β) phase and β′ phase. [ABSTRACT FROM AUTHOR]

In this work, AZ81 alloys reinforced with 3 wt%, 6 wt% and 9 wt% TC4 (Ti–6Al–4V) particles were fabricated using two-step stirring. The tensile results revealed that the TC4 particles could significantly improve the yield stress (YS), ultimate tensile stress (UTS), and elongation (El.) of AZ81 alloys. By adding TC4, the grains showed refined/coarse bimodal morphologies in the composites. The formation of β (Mg 17 Al 12) phase was notably suppressed due to the interfacial reaction between TC4 and Al. The dynamic recrystallization (DRX) behavior was also restricted by TC4 particles and β phase, ascribing to the refined grains and Orowan strengthening. The good interfacial bonding was achieved at the interface of TC4/α-Mg in 6TC4/AZ81 composite. Compared to the AZ81, 6TC4/AZ81 showed the highest YS, UTS and El. of 241 MPa, 357 MPa, and 17.0%, respectively. Its increased strength was primarily attributed to the mismatch coefficient of thermal expansion (CTE) and grain boundary strengthening. The improved ductility was ascribed to the TC4 particles, which are more deformable to withstand external load. [ABSTRACT FROM AUTHOR]

Asymmetric extrusion (AE) deformation has been proved to be an effective way to weak the basal texture of Magnesium (Mg) alloys, improving their mechanical properties. However, the influence of AE process on particle reinforced Mg-matrix composites (MMCs) remains unclear. Thus, in this paper, the effect of different deformation modes (conventional extrusion (CE) and AE) on the microstructure, texture and mechanical properties of 6 wt% Ti p /AZ31 composite were comparatively investigated. The results showed that the two extrusion methods induced disparate particle deformation zones (PDZs) effects, which mainly related to the deformation accumulation and the distribution of Ti particle (Ti p ). The microstructure characterization and finite element analysis (FEA) indicated that the Ti p distribution was uneven in the AE process compared with the CE process. In addition, the grain orientation of CE- and AE-processed samples showed a pronounced difference. The discrepancy in texture components was mainly related to the difference in the stress states of matrix and Ti particle status. The current research provides insights into the development of Ti particle reinforced Mg-based composites with great properties and structures. [ABSTRACT FROM AUTHOR]

In the present study, the microstructure and mechanical behaviors of graphene nanoplatelets (GNPs)/titanium (Ti) particles reinforced AZ91 laminate under tension along the rolling direction (RD) were systematically studied. The laminated composite with hybrid GNPs + Ti particles exhibits optimal mechanical properties, with a yield strength of 160 MPa, an ultimate tensile strength of 243 MPa, and elongation of 20.8%. Electron backscattered diffraction and slip trace analysis was conducted to reveal the mechanisms for the enhancement of strength and ductility of AZ91 by GNPs/Ti particles addition. The higher yield strength of reinforced AZ91 composites beyond the un-reinforced AZ91 laminate is mainly derived from the weakened recrystallization behavior near the interfaces by composites layers, leading to strong texture strengthening. The significantly increased ductility is derived from the higher activity of 2nd order pyramidal slip and higher energy required for crack generation and propagation by introducing reinforcement layers. Furthermore, fracture observation revealed that introducing Ti particles improved the composite's interlayer bonding properties compared with the GNPs/AZ91 composite, leading to a slight improvement in elongation. This work provides insights into the deformation mechanisms of reinforced, laminated composites, and suggests that a low-cost and straightforward processing method can be employed to fabricate structural materials. • The GNPs + Ti/AZ91 laminated composites were successfully fabricated by hot pack-rolling method. • The addition of Ti particles improved the delamination condition via forming interfacial region. • The composites' high ductility is derived from their laminated structure and higher activity of non-basal slip. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloys have a great potential for applications in the automobile, aerospace, and 3C industries due to their light weight, high specific strength, good conductivity, high damping capacity, and superior recyclability. However, the low strength and relatively low stiffness of Mg alloys seriously hinder their large-scale applications. In this work, a series of lightweight multicomponent Mg 90.5- x Al 5 Zn x Cu 4 Ce 0.5 (x = 4, 8, 14, 18, and 23 at.%) alloys with high strength and high Young's modulus were designed based on the multicomponent alloys concept to obtain a high alloying degree by precipitating a large number of high Young's modulus phases, and prepared successfully by electric resistance furnace. The present results show that these alloys exhibit an excellent combination of exceptional compressive strength (up to 627 MPa) and high Young's modulus (up to 65 GPa), which is attributed to a large number of stable intermetallic phases with high cohesive energy and high Young's modulus, as verified by first-principles calculations. Our results may have implications for the design of Mg alloys and Mg-based composites with high strength and high stiffness. [ABSTRACT FROM AUTHOR]

In this work, the extruded Mg-13Gd alloy sheet was fabricated by hot extrusion with small extrusion ratio of 3.9 (ER3.9) combined with the aging prior to extrusion (APE) treatment. The APE-ER3.9 and ER-3.9 samples show apparent heterogeneous lamella structure (HLS) and heterogeneous texture (HT), where fine dynamically recrystallized (DRXed) grains form a random texture and coarse un-DRXed grains exhibit a strong basal texture. Besides, amounts of pre-existing nano-precipitates are introduced in the APE-ER3.9 sample. The APE-ER3.9 sample exhibits the optimal combination of strength and ductility, which is attributed to the synergy of HT between coarse and fine grains, the elevated heterogeneous deformation-induced (HDI) strengthening and hardening, the pre-existing precipitates and the dynamic generation of nanoscale chain-like precipitates during deformation. The coarse grains mainly rely on the activation of basal and prismatic slips to maintain its work hardening. In fine grains, the basal slip dominates the whole deformation process, while the combined effects of activated pyramidal slip and cross slip play a significant role in accommodating the late deformation. This work provides a guide for designing Mg-RE alloys with excellent strength and ductility. [ABSTRACT FROM AUTHOR]

In the field of metal matrix composites, it is a great challenge to simultaneously improve the strength, ductility and elastic modulus of magnesium matrix composites (MMCs). In this work, Mg–3Al–1Zn composites reinforced with micron-Ti particles were prepared by powder metallurgy. The results show that the yield strength, elongation and elastic modulus simultaneously were increased with increasing content of Ti particles. Through diffusion, Ti and Al formed TiAl phase at the edge of Ti particle. A nanoscale layer of MgO formed between TiAl and magnesium (Mg) matrix. The 9Ti/Mg–3Al–1Zn composite obtained the best comprehensive mechanical properties with yield strength, ultimate tensile strength and elongation of 264 MPa, 294 MPa and 8%, respectively. The increased strength is mainly due to the grain refinement and strong interfacial bonding between Ti particles and Mg matrix. The improved ductility is the result of refined grains, weakened texture and collaborative deformation of Ti particles. [ABSTRACT FROM AUTHOR]

The size effect on ductility is not sufficiently understood and developed to be calculated by equations like that of the well-known Hall-Petch relationship for the size effect on strength. To improve the understanding of the size effect on ductility, in this work, small amount of rare earth (Sc and Y) elements were submitted to Mg–Li dual-phase alloys, possessing hexagonal-close-packed alpha-magnesium (α-Mg) and body-centra-cubic beta-lithium (β-Li) phases. An abnormally high elongation of 43%, more than two times as those of common magnesium alloys, was acquired in an as-cast Mg–Li dual-phase alloy. The abnormally high ductility possessed by Mg–Li dual-phase alloys in both this work and previous literatures, during tension and compression, was attributed to the size effect of the width of β-Li phase in this kind of alloys. The critical value of this size effect, which is believed to be twice of the interface-affected zone (IAZ), presented to lay in the range of 3–8 μ m. Based on this size effect, a duplex Mg–Li alloy, after the working process, is expected to achieve a high elongation via making the width of β-Li phase to satisfy the critical value presented in this work. [ABSTRACT FROM AUTHOR]

Hot compressive deformation mechanism of the carbon-contained face-centered cubic CoCrFeMnNi high-entropy alloy (HEA) was investigated in the temperature range between 700 °C and 1000 °C and in the strain rate range between 0.001 and 1 s−1. The constitutive equation of CoCrFeMnNiC 0.5 (at.%) alloy was obtained, which can predicate the flow stresses accurately. The apparent activation energy (Q) was calculated as 362 kJ/mol, suggesting that the carbon addition cause the work hardening during hot deformation. The deformation mechanisms at various Zener–Hollomon parameter values have been discussed. The Zener-Hollomon parameter (lnZ) of CoCrFeMnNiC 0.5 alloy deformed at 700 °C increases with the increasing of the strain and strain rate. At low Zener-Hollomon condition (lnZ≤40), density dislocation walls (DDWs) caused the obvious work hardening by producing a long-range back stress. With the lnZ increasing, the addition of carbon in solid solution effectively reduces the dislocation cross-slip, and causes the transition from well-development DDWs to microbands (MBs). MBs can be regarded as another imported deformation mode to provide additional work-hardening source. At high Zener-Hollomon condition (lnZ>46), the pronounced effect of MBs results in slight increasing of the flow stress after steady flow. The Zener-Hollomon parameter of CoCrFeMnNiC 0.5 HEA deformed at ε = 0.8 decreases with the temperature increasing and strain rate decreasing. Discontinuous dynamic recrystallization (DDRX) is the dominant microstructural evolution mechanism and leads the flow softening at low lnZ condition (lnZ≤40). The DDRX nucleation is attributed to the microbands and pinning effect on the dislocation movement induced by M 23 C 6 carbides, which can lead to local grain boundary expansion. [ABSTRACT FROM AUTHOR]