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This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain structure of the alloys, designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe (wt%) alloy with high strength and formability. With the increase of Zn content, forming the coupling distribution of multiscale precipitates and iron-rich phases with a reasonable matching ratio and dispersion distribution characteristics is easy. This phenomenon induces the formation of cell-like structures with alternate distribution of coarse and fine grains, and the average plasticity–strain ratio (characterizing the formability) of the pre-aged alloy with a high strength is up to 0.708. Results reveal the evolution and influence mechanisms of multiscale second-phase particles and the corresponding high formability mechanism of the alloys. The developed coupling control process exhibits considerable potential, revealing remarkable improvements in the room temperature formability of high-strength Al–Zn–Mg–Cu alloys. [ABSTRACT FROM AUTHOR]

Low-alloyed magnesium (Mg) alloys have emerged as one of the most promising candidates for lightweight materials. However, their further application potential has been hampered by limitations such as low strength, poor plasticity at room temperature, and unsatisfactory formability. To address these challenges, grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys. An effective way for regulating grain structure is through grain boundary (GB) segregation. This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys. The analysis encompasses both single element segregation and multi-element co-segregation behavior, considering coherent interfaces and incoherent interfaces. Furthermore, we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties. Drawing upon these studies, we propose strategies for the design of high mechanical performance Mg alloys with desirable properties, including high strength, excellent ductility, and good formability, achieved through the implementation of GB segregation. The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.

• The review summarized the interface segregation behavior of Mg alloys, including segregation sites of coherent and incoherent interfaces, and the effect of grain boundary segregation on static recrystallization and grain growth. • The latest developments and breakthrough of low-alloyed Mg alloys were summarized. • The strategies for designing low-alloyed Mg alloys with high plasticity/strength/formability were proposed. Low-alloyed magnesium (Mg) alloys have emerged as one of the most promising candidates for lightweight materials. However, their further application potential has been hampered by limitations such as low strength, poor plasticity at room temperature, and unsatisfactory formability. To address these challenges, grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys. An effective way for regulating grain structure is through grain boundary (GB) segregation. This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys. The analysis encompasses both single element segregation and multi-element co-segregation behavior, considering coherent interfaces and incoherent interfaces. Furthermore, we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties. Drawing upon these studies, we propose strategies for the design of high mechanical performance Mg alloys with desirable properties, including high strength, excellent ductility, and good formability, achieved through the implementation of GB segregation. The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization. [ABSTRACT FROM AUTHOR]

A novel idea of precisely constructing gradient heterogeneous microstructure was proposed to greatly improve the formability of Al-Zn-Mg-Cu alloy by coupling multi-process firstly. After coupling control of the heterogeneous distribution of precipitates, strain energy storage and dislocation number density, a gradient distribution of coarse/fine grains can be constructed in the pre-aged alloy, resulting in a greatly enhanced average plastic strain ratio of 0.716. This work opens up a new frontier for achieving super-high room temperature formability without sacrificing the high strengths for Al-Zn-Mg-Cu alloys.

A novel idea of precisely constructing gradient heterogeneous microstructure was proposed to greatly improve the formability of Al-Zn-Mg-Cu alloy by coupling multi-process firstly. After coupling control of the heterogeneous distribution of precipitates, strain energy storage and dislocation number density, a gradient distribution of coarse/fine grains can be constructed in the pre-aged alloy, resulting in a greatly enhanced average plastic strain ratio of 0.716. This work opens up a new frontier for achieving super-high room temperature formability without sacrificing the high strengths for Al-Zn-Mg-Cu alloys. This paper reports a gradient heterogeneous structure in Al-Zn-Mg-Cu alloys by coupling control of precipitates, strain energy storage and dislocation number density, resulting in a greatly enhanced average plastic strain ratio of 0.716. [ABSTRACT FROM AUTHOR]

Conventional hole-flanging by stamping is characterized by low formability. It is common knowledge that formability can be improved by forming at high temperatures. High-speed punch rotation is introduced to conventional hole-flanging to use frictional heat to improve and control formability. Thermomechanical finite element (FE) simulations of conventional hole-flanging and hole-flanging with punch rotation are used to determine the effects of punch rotation on the process temperature. Hot tensile tests were conducted to find the effects of temperature and strain rate on the forming limit of the blank. The Marciniak–Kuczynski (M–K) forming limit model is used to estimate temperature and strain-rate dependent forming limits of the material. Hole flanging experiments were conducted at different punch speeds and feeds to determine process windows that maximize formability. A maximum hole expansion ratio (HER) of 4 was obtained in hole-flanging with punch rotation compared to 1.48 in conventional hole-flanging experiments. In theory, a rise in blank temperature to 400 °C in hole-flanging with punch rotation enhances the HER by 30% based on the FE simulations. However, experiments of hole-flanging with punch rotation reveal a 170% increase in formability. The difference in formability between the experiments and FE simulations is attributed to the influence of high-speed deformation, in-plane shear and non-proportional loading paths. To control formability in hole-flanging with high-speed punch rotation, it seems sufficient to establish a closed-loop control of the process with a pre-defined temperature profile. [ABSTRACT FROM AUTHOR]

A novel TiC p /Mg-4Zn-0.5Ca nanocomposite was successfully developed by using the ultrasonic-assisted semisolid stirring method, and then extruded at the speed of 0.01 mm/s with low extrusion temperatures of 270, 230 and 190 °C, respectively. The experimental results indicated that ultrasonic-assisted semisolid stirring could be able to realize the uniform distribution of nano-sized TiC p in the nanocomposite. The external addition of TiC nanoparticles refined the grain dimension of the matrix alloy and improved the morphology of eutectic Ca 2 Mg 6 Zn 3 phases. The particle stimulated nucleation caused by TiC p provided large driving force for the dynamic recrystallization at the low temperature of 190 °C, leading to high volume fraction of recrystallized grains and formability of TiC p /Mg-4Zn-0.5Ca nanocomposite. The smallest grain size of ∼0.34 μm obtained at 190 °C was caused by two factors, one was due to the temperature reduction, the other was attributed to the coordination pinning effect of nano-scale TiC particles with MgZn 2 precipitates. The elongation of the present nanocomposite extruded at 270 °C was improved by 158.2% than the level in as-extruded matrix alloy. This could be ascribed to that the addition of TiC nanoparticles could act as nucleation sites for the recrystallization, and thus coordinate the deformation of matrix. The tensile strength increased as the extrusion temperature decreased, YS of ∼355.3 MPa, UTS of ∼385.7 MPa and EL ∼10.2% were obtained for the TiC p /Mg-4Zn-0.5Ca nanocomposite extruded at 190 °C. The excellent mechanical properties were associated with combining effects of the addition of TiC nanoparticles, grain refinement and a large amount of precipitated MgZn 2 phases. Image 1 • TiC nanoparticles were successfully added to the Mg-4Zn-0.5Ca matrix alloy. • The formability at lower temperature was improved by the added TiC nanoparticles. • TiC nanoparticles and precipitated phases contributed to improved tensile strength. [ABSTRACT FROM AUTHOR]

Here we report a heterogeneous microstructure in Al–Zn–Mg–Cu alloys by coupling control of solute gradient distribution, multiscale iron-rich phases and a novel thermomechanical processing that can produce a greatly improved formability (the average plastic strain ratio r = 0.719). A heterogeneous structure of coarse grains surrounded by fine grains is formed, and an unusual high formability is obtained by the synergy of soft/hard microdomains. The process discovered here is amenable to large-scale automotive industrial production at low cost, and might be applicable to other Al alloy systems. [ABSTRACT FROM AUTHOR]