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The predeformation prior to artificial aging plays an important role in enhancing the properties of Al–Cu–Li based alloys. This study focused on investigating the impact of a large amount of prerolling (20%) on the orientation variation and distribution characteristics of T1 precipitates in a rolled Al–Cu–Li alloy. The results revealed that T1 phases precipitated in the same orientation were not strictly parallel within a grain, a small angle existed between different phases in the same direction due to the orientation fluctuation of the matrix induced by prerolling. The misorientation degree of the T1 precipitates presented a slight expend tendency with increasing the aging time. Furthermore, the connection between this orientation distortion of the T1 phases and the tensile properties was discussed. Additionally, it was found that the T1 variants along different orientations were heterogeneously distributed, possibly due to the activation of different slip systems during the prerolling process and the variation in the number of nucleation sites among the nonparallel habit planes. [ABSTRACT FROM AUTHOR]

Comparison of the precipitation characteristics of the Al-Cu-Li alloys under different processing states, especially in the presence or absence of thermoplastic deformation, was of little concern in previous studies. In this article, samples of an Al-Cu-Li alloy with different processing states were prepared, then the differences in precipitation behavior of these samples during 200 °C aging were examined, and the internal factors affecting the aging precipitation were also discussed. It was found that the processing states have a significant influence on precipitation dynamics and characteristics for the investigated alloy. The types of peak-aged precipitates and the density, size of the main strengthening phase show a great difference among the assessed states. Further analysis suggested that the integrated effect of dislocation and vacancy may be the internal reason that accounted for the differences in characteristics of precipitates between the cast alloy and the rolled alloy, as well as the different promotional effects of the pre-rolling and pre-stretching on precipitation of the T1 (Al2CuLi) phase. [ABSTRACT FROM AUTHOR]

In this paper, the effects of compressive pre-deformation and successive pre-artificial aging on the compressive creep aging behavior and microstructure evolution of the Al-Cu-Li alloy have been studied. Severe hot deformation mainly occurs near the grain boundaries during the compressive creep initially, which steadily extends to the grain interior. After that, the T1 phases will obtain a low radius–thickness ratio. The secondary T1 phases in pre-deformed samples usually only nucleate on dislocation loops or Shockley incomplete dislocations induced by movable dislocations during creep, which are especially prevalent in low plastic pre-deformation. For all pre-deformed and pre-aged samples, two precipitation situations exist. When pre-deformation is low (3% and 6%), solute atoms (Cu and Li) can be consumed prematurely during pre-aging at 200 °C, with dispersed coherent Li-rich clusters in the matrix. Then, the pre-aged samples with low pre-deformation no longer have the ability to form secondary T1 phases in large quantities during subsequent creep. When dislocation entangles seriously to some extent, a large quantity of stacking faults, together with a "Suzuki atmosphere" containing Cu and Li, can provide the nucleation sites for the secondary T1 phase, even when pre-aged at 200 °C. The sample, pre-deformed by 9% and pre-aged at 200 °C, displays excellent dimensional stability during compressive creep because of the mutual reinforcement of entangled dislocations and pre-formed secondary T1 phases. In order to decrease the total creep strain, increasing the pre-deformation level is more effective than pre-aging. [ABSTRACT FROM AUTHOR]

This paper studies the influence of the regression re‐aging (RRA) process on the mechanical properties and corrosion resistance of 7075. In the RRA heat treatment, the material properties are markedly affected by the variation of parameters in the regression stage. When the regression temperature and the regression duration increase, the mechanical properties of the material decrease. There was no intergranular corrosion in the samples treated by RRA, while obvious intergranular corrosion occurred in the T6 sample. Compared with the T6 sample, the RRA‐190‐0.5 sample with optimized parameters has a higher density of the precipitated phase and narrower precipitate‐free zone, and the precipitated phase along the grain boundary is discontinuous, isolated, and short. Compared with the single‐stage peak aging treatment, the RRA treatment can considerably improve the corrosion resistance and stress corrosion resistance but slightly reduce the strength. The best heat treatment process condition is 120°C/24 h + 190°C/0.5 h + 120°C/24 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anisotropic hardness evolution appears during artificial aging when changing the loading axis of samples. • Due to fiber texture and inhomogeneous distribution of T 1 (Al 2 CuLi) variants, different amounts of face-on/inclined T 1 will be encountered in different loading directions. • The face-on/inclined T 1 has a higher resistance ability to hardness loading compared to edge-on T 1. • The pre-stretching prior to aging can effectively facilitate the isotropy of hardness evolution. Anisotropy of mechanical properties has limited the further application of Al–Cu–Li alloys. Previous research efforts were mostly focused on the anisotropic tensile properties. In the present study, significant hardness anisotropy evolution, measured during artificial aging, was also established when loading in different directions. It was found that different amounts of inclined/face-on would be encountered when loading along different directions, resulting from the fiber texture and inhomogeneous distribution of T 1 (Al 2 CuLi) variants along different directions for the samples without pre-stretching. The resistance to hardness loading is different between the face-on/inclined T 1 and edge-on T 1 due to its high aspect ratio, so the measured anisotropic hardness is obtained. Moreover, the characteristics of precipitates also play an important role in the anisotropic hardness evolution, the strong anisotropy of hardness only appears in the alloys that contained large diameters and a low density of T 1 phase or θ' (Al 2 Cu) phase. After applying pre-stretching, the predominant T 1 phase precipitates with small diameters and a high density, which helps to facilitate the isotropic hardness evolution during artificial aging. These findings provide a necessary supplement for the hardness evaluation where a high aspect ratio of precipitate is involved. [ABSTRACT FROM AUTHOR]

[Display omitted] • The microstructures of homogenized alloy are greatly affected by the cooling rates. • The air-cooled sample is dominated by T phase and δ′/β′ phase. • In the furnace cooling, numerous large size T 1 phases and some θ′ liked phases are precipitated. The microstructure of homogenized Al–Cu–Li alloy is greatly affected by cooling rates. The air-cooled sample is dominated by high temperature precipitated T (Al 20 Cu 2 Mn 3) phase and β′ (Al 3 Zr) phase, accompanied by naturally aged δ′ (Al 3 Li) phase. But for the furnace cooled sample, except for the T phase and δ′/β′ phase, the predominant phases are numerous micrometer-scale T 1 (Al 2 CuLi) phase and some of θ′ (Al 2 Cu) liked phase. [ABSTRACT FROM AUTHOR]

The aging Al–Zn–Mg–Cu alloy exhibits a significant decrease in performance after undergoing thermal shock. In order to improve the resistance of this type of alloy to thermal shocks, the influence of deep cryogenic treatment (DCT) on the high temperature mechanical properties and microstructure of thermal shocked Al–Zn–Mg–Cu alloy is investigated in this paper. It was found that the mechanical properties of Al–Zn–Mg–Cu alloys decrease significantly with the increase of electric heating temperature. The deep cryogenic treatment reduced the grain size of Al–Zn–Mg–Cu alloy, increased the density of the precipitates, and also inhibited the coarsening of the precipitates. Therefore, the deep cryogenic treatment can slow down the weakening effect of Al–Zn–Mg–Cu alloy at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, Cu-W alloys with different TiC additions were prepared by wire arc additive manufacturing (WAAM) technology with Cold Metal Transfer (CMT) melting copper-based flux cored wire. In the additive manufacturing process, W and TiC with high melting point directly transited to the molten pool as solid phase. When the addition of TiC was small, most of TiC was gathered around the W particles in Cu-W alloys, which was conducive to enhancing interface bonding strength. With the increased of TiC content, the electrical conductivity of Cu-W alloys was decreased, microhardness and high temperature wear resistance were increased. When the addition of TiC was more than 3 wt%, the agglomeration of TiC degrades the performance of Cu-W alloys. Cu-W alloys with 3 wt% TiC addition show the best performance, includes high microhardness and high wear resistance with low loss of electrical conductivity. In this paper, Cu-W alloys were prepared by wire arc additive manufacturing method, and the mechanical properties of the samples with different TiC additions were analyzed and characterized, and the mechanism of property changes with different TiC additions was revealed. This study provides a new idea for the preparation of Cu-W composites. [Display omitted] • TiC reinforced Cu-W alloy prepared sucessfully using WAAM. • The addition of TiC improves the high-temperature wear resistance of Cu-W alloy. • Adding TiC can increase interfacial bonding strength due to diffusibility of TiC with W and Cu. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mo 15 Nb 20 Ta 10 Ti 35 V 20 with BCC structure was prepared by vacuum arc melting. • Mo 15 Nb 20 Ta 10 Ti 35 V 20 with superior anti-corrosion compared to 316 stainless steel. • Mo 15 Nb 20 Ta 10 Ti 35 V 20 presented a unique secondary passivation phenomenon. • The primary and secondary passive films had different P-N junctions. • The dynamic changes of TiO 2 and Ti 2 O 3 contents caused secondary passivation. The Mo 15 Nb 20 Ta 10 Ti 35 V 20 refractory high entropy alloy with BCC structure was prepared by vacuum arc melting. The synthesized Mo 15 Nb 20 Ta 10 Ti 35 V 20 demonstrated better corrosion resistance compared to 316 stainless steel in chloride corrosion environment, whose better corrosion resistance is attributed to the complex passive film structure and shows the characteristics of passivation-transpassivation-secondary passivation on the polarization curve. Mott-Schottky curves analysis and XPS results show that the primary and secondary passive films have different P-N junctions which were composed of different oxides showing bilayer structure characteristics. Through the thermodynamic calculation, the relationship between the competitive growth of multiple principal elements in RHEA were analyzed. The dynamic changes of TiO 2 and Ti 2 O 3 contents were responsible for the secondary passivation phenomenon. [ABSTRACT FROM AUTHOR]