Effect of stretching on the precipitation kinetics on an Al-2.0Li-2.8Cu-0.5Mg({minus}0.13Zr) alloy

Journal Article · Wed Dec 01 04:00:00 EST 1993 · Metallurgical Transactions, A

DOI:https://doi.org/10.1007/BF02659485· OSTI ID:142313

Kim, J D; Park, J K ^[1]

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1. Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering

The influence of stretching on the precipitation kinetics of an Al-2.0Li-2.8Cu-0.5Mg({minus}0.13Zr) alloy has been quantitatively investigated using transmission electron microscopy (TEM) and hardness testing. The microstructure of the alloy consists primarily of {delta}{prime}, S{prime}, and T{sub 1} phases. Stretching exerts little influence on the coarsening kinetics of {delta}{prime} phase. The activation energy for coarsening is estimated to be {approximately}100 kJ/mole, regardless of whether the alloy is unstretched or stretched. The volume fraction of {delta}{prime} phase, however, is significantly reduced in the stretched condition. The stretching treatment greatly accelerates the nucleation kinetics of T{sub 1} phase at the expense of S{prime} phase; however, the growth rate of T{sub 1} phase (and also of S{prime} phase) is significantly reduced in the stretched condition due to overlapping of the diffusion field. A kinetic model is presented the addresses this problem. The model successfully predicts the effect of stretching on the lengthening rate of T{sub 1} plates. The activation energies for the lengthening of T{sub 1} plates and S{prime} rods are {approximately}100 to 110 kJ/mole and {approximately}110 to 120 kJ/mole, respectively, regardless of the condition of stretch. It is concluded that, for both unstretched and stretched material, the growth of the T{sub 1} and S{prime} phases is controlled by the diffusion of copper along dislocations. The nucleation of S{prime} phase tends to occur at dislocations with a Burgers vector that is nearly parallel to the [010]{sub s} direction, which is the direction that exhibits maximum misfit.

• Sponsoring Organization: USDOE
• OSTI ID: 142313
• Journal Information: Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 12 Vol. 24A; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
COPPER ALLOYS
KINETIC EQUATIONS
LITHIUM ALLOYS
MAGNESIUM ADDITIONS
MATHEMATICAL MODELS
PHASE STUDIES
PRECIPITATION HARDENING
ZIRCONIUM ADDITIONS