Microstructural evolution of Mg, Ag and Zn micro-alloyed Al–Cu–Li alloy during homogenization

Zhang

et al. 2021

Materials

The mechanical properties of Al-Cu-Li alloys after different pretreatments were investigated through tensile testing at 25 and −196 °C, and the corresponding microstructure characteristics were obtained through optical metallography, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. An increasing mechanism of both strength and ductility at cryogenic temperatures was revealed. The results show that the hot deformation pretreatment before homogenization promoted the precipitation of Al3Zr particles, improved particle distribution, and inhibited local precipitation-free zones (PFZ). Both hot deformation pretreatment before homogenization and cryogenic temperature were able to improve strength and ductility. The former improved strength by promoting the precipitation of Al3Zr particles while enhancing the strengthening effect of the second-phase particles and reducing the thickness of the coarse-grained layer. Meanwhile, the increase in ductility is attributable to the decrease in thickness of the coarse-grained layer, which reduced the deformation incompatibility between the coarse and fine grains and increased the strain-hardening index. The latter improved the strength by suppressing dynamic recovery during the deformation process, increasing the dislocation density, and enhancing the work hardening effect. Additionally, the increase in ductility is attributable to the suppression of planar slip and strengthening of grain boundaries, which promoted the deformation in grain interiors and made the deformation more uniform.

Section: Introductionmentioning

confidence: 99%

Effect of Pretreatment and Cryogenic Temperatures on Mechanical Properties and Microstructure of Al-Cu-Li Alloy

Zhang

et al. 2021

Materials

“…The diffusion mechanism and specific role of Zn in the homogenization process are not yet clear. In addition, the Mg-Zn atom clusters were detected in many aging Al-Cu-Li-Mg-Zn alloys, which displayed similar characteristics to the Mg-Ag atom clusters observed in the Al-Cu-Li-Mg-Ag alloys [18][19][20]. It is possible to form the enrichment of Mg-Zn atom clusters in the alloy during solidification as well.…”

Section: Introductionmentioning

confidence: 55%

Investigation on Microstructural Evolution and Properties of an Al-Cu-Li Alloy with Mg and Zn Microalloying during Homogenization

et al. 2018

Metals

The microstructural evolution and properties of an Al-Cu-Li alloy with Mg and Zn microalloying (Al-3.5Cu-1.5Li-0.5Mg-0.4Zn-0.3Mn-0.12Zr-0.06Ti) ingot subjected to homogenization (second-step annealing at 500 °C for 24 h following first-step annealing at 400 °C for 8 h) were investigated. Mg-Zn atom clusters were enriched at the end of dendrites as well as low-melting eutectic phases such as S (Al2CuMg), T2 (Al6CuLi3), TB (Al7.5Cu4Li) and T1 (Al2CuLi) in the as-cast alloy. During homogenization, Mg-Zn atom clusters diffused from the segregation to the vacancies, leading to the dissolution of the low-melting eutectic phases. Not only Al3Zr particles were observed at 500 °C, but more fine and uniform spherical dispersoids appeared, which were assumed as Al3(ZrxTiyLi1−x−y). Mg and Zn microalloying can promoted the nucleation of Al3Zr and Al3(ZrxTiyLi1−x−y) dispersoids, as well as T (Al20Cu2Mn3) phases, which all inhibited recrystallization effectively and improve the uniformity of the grains due to the strong pinning effect. The yield ratio was decreased from 0.81 to 0.52 with the yield strength decreased from 172 MPa to 61 MPa, which showed better plastic deformation ability of the alloy subjected to homogenization. In addition, the dissolution of low-melting eutectic phases and formation of Al3(ZrxTiyLi1−x−y) dispersoids resulted in the significant improvement on thermal stability.

“…In this section we will describe the change of solid solubility of alloy elements of 2195 as-cast alloys in the different electromagnetic casting conditions from the aspects of thermodynamics and crystallography. From the point of view of thermodynamics, the remelting of eutectic phases at grain boundary accompanies with the change of the enthalpy [22], it can be exhibited and analyzed by differential scanning calorimetry (DSC) measurement. The results of DSC test of 2195 as-cast alloys cast by DCC and LFEC are shown in Fig.…”

Section: Effects Of Lfec On Intra-granular Solid Solubility Of Alloy mentioning

confidence: 99%

Low Frequency Electromagnetic Casting of 2195 Aluminum–Lithium Alloy and Its Effects on Microstructure and Mechanical Properties

Acta Metall. Sin. (Engl. Lett.)

Sun

Fang

et al. 2020

In this study, the low frequency electromagnetic casting (LFEC) technology was adopted to fabricate 2195 Al-Li alloy. The microstructure and solid solubility of as-cast 2195 alloys, as well as the second phase precipitation and tensile properties after aging, were investiagated and compared with the counterpart direct chill casting 2195 alloy. Our results indicate that LFEC can significantly improve the microstructure and metallurgical quality of as-cast alloy, and increase the number density of θ′ (Al 2 Cu) and T 1 (Al 2 CuLi) phases during aging treatment due to the enhanced solubilities of alloying elements. The tensile properties of 2195 aged alloy cast by LFEC were hence improved evidently.