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MM: Metall- und Materialphysik

MM 8: Symposium Modern Metallic Materials Design II

MM 8.5: Vortrag

Montag, 27. März 2006, 15:45–16:00, IFW B

First-principles studies on the precipitation thermodynamics of Al-Cu alloys — •Shaoqing Wang and Hengqiang Ye — Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China

The technique of precipitation hardening is widely used for strengthening alloy materials in metallurgical industry. We studied the structure and ground-state energetics of Guinier-Preston (GP) precipitates in Al-Cu alloys. An atom-scale mechanism for the formation and structure evolution of GP zones in Al-Cu alloys was proposed [1]. The precipitation is a thermodynamic phenomenon. For a thorough understanding of the matter, it is essential to investigate the thermodynamic aspect of the process. In present work, we study the precipitation thermodynamics of Al-Cu alloys by first-principles response-function calculation [2]. The optimized atomic configurations of Al-Cu superlattices [1] for different Cu content are adopted as the starting point. We firstly calculate the dynamical matrices of Al-Cu superlattices for a set of special q-points. Then the full phonon spectrum is obtained by the Fourier interpolation algorithm of dynamical matrices [3]. From these full phonon spectrums, the temperature dependences of Helmholtz free energy and entropy of these Al-Cu superlattices are calculated. The structure evolution of GP precipitation as temperature decreases is reasonably interpreted.

[1] S. Q. Wang, M. Schneider, H. Q. Ye, G. Gottstein, Scripta Mater. 51, 665 (2004).

[2] X. Gonze, Phys. Rev. B 55, 10337 (1997).

[3] S. Baroni et al., Rev. Mod. Phys. 73, 515 (2001).