The thermodynamics of and strengthening due to co-clusters: General theory and application to the case of Al–Cu–Mg alloys

✍ Scribed by M.J. Starink; S.C. Wang

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 620 KB
• Volume: 57
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2009.01.021

✦ Synopsis

Co-clusters in ternary or higher order metallic alloys are metastable structures involving two or more distinct alloying atoms that retain the structure of the host lattice. A thermodynamic model based on a single interaction energy of dissimilar nearest neighbour interaction energy is presented, and a model for the strengthening due to these co-cluster dimers is derived. The model includes a new treatment of (short-range) order strengthening relevant to these co-clusters and further encompasses modulus hardening and chemical hardening. The models are tested against data on a wide range of Al-Cu-Mg alloys treated at temperatures between 20 and 220 °C. Both quantitative calorimetry data on the enthalpy change due to co-cluster formation and strengthening due to co-clusters is predicted well. It is shown that in general (short-range) order strengthening will be the main strengthening mechanism.