Effect of Different Aging Processes on the Microstructure and Mechanical Properties of a Novel Al-Cu-Li Alloy

doi:10.1016/j.jmst.2016.01.018

Abstract

Abstract:

The effects of different aging processes on the microstructure and mechanical properties of a novel Al-Cu-Li alloy have been investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the tensile properties of a novel Al-Cu-Li alloy are sensitive to aging processes, which correspond to different microstructures. σ (Al₅Cu₆Mg₂) and T₁ (Al₂CuLi) phases are the major precipitates for the alloy in T6 aging condition (165 °C/60 h). After duplex aging condition (150 °C/24 h + 180 °C/12 h), σ, θ' (Al₂Cu) and T₁ phases are detected. Only the T₁ phases can be found in the T8 state alloy (6% pre-strain+135 °C/60 h). The failure modes of alloy in T6 and duplex aging conditions are dimple-intergranular fracture, while typical quasi-cleavage fracture in T8 condition.

Key words: Al-Cu-Li alloy, Aging process, Microstructure, Mechanical properties

Li Hongying,Huang Desheng,Kang Wei,Liu Jiaojiao,Ou Yangxun,Li Dewang. Effect of Different Aging Processes on the Microstructure and Mechanical Properties of a Novel Al-Cu-Li Alloy[J]. J. Mater. Sci. Technol., 2016, 32(10): 1049-1053.

Figures/Tables 8

Table 1 Aging treatment procedures used for a novel Al-Li alloy in this study

Number	Condition	Heat treatment procedure
1	T6	165 °C/60 h
2	T8	6% pre-strain + 135 °C/60 h
3	Duplex aging	150 °C/24 h + 180 °C/12 h

Fig. 1. Dimensions of the tensile sample.

Fig. 2. Tensile properties of a novel Al-Cu-Li alloy sample with various heat treatments.

Fig. 3. Fractographs of the tensile specimens under conditions of T6 (a, b), T8 (c, d), and duplex aging (e, f).

Fig. 4. TEM images of specimens under different aging conditions: (a) BF image of solid solution state taken along [001]Al; (b) BF image of T6 taken along [110]Al; (c) BF image of T8 taken along [110]Al; and (d) BF image of duplex aging taken along [110]Al.

Fig. 5. XRD patterns of a novel Al-Cu-Li alloy at various aged processes.

Fig. 6. Morphology of σ phase: (a) Moire fringe and (b) HRTEM.

Fig. 7. Grain-boundary precipitates and PFZ observed in studied alloy: (a) T6 aging, (b) duplex aging and (c) T8 aging.

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