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The 7075 aluminium alloy was treated by combining pre-aging and thermomechanical treatment to obtain excellent comprehensive properties. The properties of the alloy were investigated by hardness, exfoliation corrosion, intergranular corrosion, and electrochemical corrosion test. The microstructure of the alloy was observed by transmission electron microscopy. Furthermore, the relationship between microstructure evolution and performance change was investigated. The results showed that the hardness and corrosion resistance of the alloy were improved after the combination of pre-aging and thermomechanical treatment. With the change in the pre-aging temperature, the microstructure of the alloy changed significantly. The matrix precipitates were numerous, fine, and uniformly distributed, which significantly improved the hardness of the alloy, resulting in a peak hardness of 195.2 HV. The grain boundary precipitates were rounded and independent, the distance between the precipitates became large, and the discontinuous distribution was very obvious, which destroyed the formation of corrosion channels, hindered the development of corrosion, and effectively improved the corrosion resistance of the alloy. The exfoliation corrosion rating was P. The minimum depth of intergranular corrosion was 29.3 µm. The self-corrosion current density and corrosion rate were the lowest, 0.0013 mA/cm2 and 0.0427 mm/a, respectively. • Combined with pre-aging and T8 treatment make alloy achieve excellent comprehensive properties. • Pre-aging treatment promotes the formation of precipitated phases. • The synergistic effect of the GP zones and dislocations leading to a more uniform deformation. • Discontinuous distribution of grain boundary precipitates after pre-aging treatment. [ABSTRACT FROM AUTHOR]

Zr 55.7 Cu 22.4 Ni 7.2 Al 14.7 alloy rods with a diameter of 3 mm were prepared by copper mold suction casting. The structure, thermodynamic properties and plastic deformation behavior of the specimens before and after compression in supercooled liquid region were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and uniaxial compression machine (equipped with a high-temperature oven). The range of thermal forming process parameters was also discussed. The results show that the alloys have obvious glass transition and crystallization kinetics, and the crystallization activation energies obtained by the Kissinger and Ozawa equations are 297.1 kJ/mol and 294.9 kJ/mol, respectively. The amorphous alloys exhibit stress overshoot in low temperature region at high strain rates and deformation behavior of alloy softening in high temperature region at medium to high strain rates. Meanwhile, the viscosity of the alloy remains approximately constant at 740 K and 750 K, showing Newtonian fluid characteristic. It can be concluded that the optimal thermoplastic forming process ranges from 740 K to 750 K, 5 × 10−4 s−1 to 5 × 10−3 s−1. The crystallization activation energies of the specimens after deformation are slightly higher than before, and they increase with the increase of strain rate. • Zr-based bulk amorphous alloy has a good thermodynamic stability, which facilitates thermoplastic forming. • The amorphous alloy shows superplastic deformability at high temperatures and strain rates. • The crystallization activation energies of the deformed specimens are higher than that of the undeformed. • The crystallization activation energies of the alloys after deformation increase with increasing strain rate. [ABSTRACT FROM AUTHOR]

It is recognized that new environmentally friendly and economical cooling methods are needed. In this paper, we focus on the effect of different doping amounts of Pr on the performance of magnetic refrigeration materials in the presence of trace doping of Co ions at the B-site. The samples La 0.67 Sr 0.33−x Pr x Mn 0.975 Co 0.025 O 3 (LSPMCO x = 0.10,0.125 and 0.15) in this paper were prepared by sol-gel method. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) diffraction data determined that the samples were pure phases without impurities belonging to the R-3c space group (No. 167). Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the samples were not regular particles of submicron size, and the size of the grains decreased gradually with increasing Pr doping. The experimental data have shown that the samples underwent second order phase transitions near the Curie temperature (Tc). Tc is closest to room temperature at 300 K at a doping level of 0.10. The maximum magnetic entropy change (− ∆ S M max ) at 5 T is 3.79 (J/kg∙K) (x = 0.15) and the relative cooling power (RCP) is 352.78 (J/kg) (x = 0.15). The results demonstrated that the doping of Pr has an enhanced effect on the performance of the magnetic refrigeration La 0.67 Sr 0.33 Mn 0.975 Co 0.0 2 5 O 3 material. This may provide a reference for improving the performance of magnetic refrigeration materials in future research. • The maximum magnetic entropy change (− ∆ S M max ) with an applied magnetic field (H) of 5 T reached 3.73 J/(kg·K) at x = 0.125. • The values of LSPMCO (x = 0.10, 0.125 and 0.15) RCP were 107.41 (J/kg), 113.49 (J/kg) and 123.89 (J/kg) at 2 T. At H of 5 T X = 0.15 it reaches 306.28 (J/kg) which is 86 % of gadolinium. • LSPMCO has a large half-peak width of 92.84 at x = 0.15. LSPMCO has the potential to be further investigated as a magnetic refrigeration material. [ABSTRACT FROM AUTHOR]

The dynamic recrystallization (DRX) behavior during grinding and static recrystallization (SRX) behavior during thermal exposure of Ni-based single crystal alloy were compared in this work. The microstructure changes after DRX and SRX were characterized by field emission scanning electron microscopy (FE-SEM) and scanning transmission electron microscopy (STEM). The grain orientation and dislocation density distribution were analyzed by transmission Kikuchi diffraction (TKD) and electron backscatter diffraction (EBSD). The results show that SRX is affected by DRX process on the ground subsurface of single crystal alloy. The nucleation sites of SRX at high temperature are derived from significant number of high-density dislocation structures generated by DRX that induced by grinding process. Compared with the equiaxed nanograins produced by DRX, micron-scale cellular and equiaxed grains are formed on the surface, and dislocation density decreases sharply after SRX. The original cube texture of single crystal superalloy changes into shear texture due to plastic deformation during grinding, and then into strong recrystallization texture at high temperature. The microstructure changes under deformation and high temperature directly affect the final properties of single crystal blades. It is of great practical significance to understand the microstructure evolution and grain orientation changes during DRX and SRX processes, so as to reveal the mechanism of single crystal transforming into polycrystal from machining process to service stage of single crystal blades. • The relationship between dynamic recrystallization and static recrystallization of single crystal alloy is established. • The microstructure evolution of machined surface from single crystal to polycrystalline is revealed. • The orientation and texture changes of the recrystallized grains were obtained. [ABSTRACT FROM AUTHOR]

To modify the poor plasticity of bulk metallic glasses (BMGs) under room temperature, the present work reported that microalloying can improve the plasticity of BMGs, and the deformation mechanism at room temperature was elucidated. The selection of minor elements, Nb and Ta have a positive heat of mixing with the based compositions. The maximum plasticity of 32.9% is shown in the Nb1 sample. The self-organize to a critical state (SOC) occurred in all BMGs, the scaling exponent β value maintains the constant 0.24. The variation of the rotation angle of primary shear bands (SBs) is in agreement with plasticity. Meanwhile, the yield strength is linearly dependent on the local fracture toughness of BMGs. Summarily, the compressive plasticity of BMGs at room temperature can be improved by adding elements that can form positive mixing heat with the components of based compositions. • The maximum plasticity at room temperature of 32.9% when Nb is added at 1 at%. • The effect of Nb and Ta addition on self-organize intermittent plastic flow of bulk metallic glasses is investigating. • We expound that the correlation between the rotation mechanism and compressive plasticity in the bulk metallic glasses. • The fracture toughness of local plasticity region is calculated, which linearly dependent on the yield strength of BMGs. [ABSTRACT FROM AUTHOR]