中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 24 No. 7 July 2014 |
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering of Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The retrogression kinetics for grain boundary precipitate (GBP) of 7A55 aluminum alloy was investigated by transmission electron microscopy (TEM) observation. The results reveal that the coarsening behavior of GBP obeys “LSW” theory, namely, the cube of GBP average size has a linear dependence relation to retrogression time, and the coarsening rate accelerates at the elevated retrogression temperature. The GBP coarsening activation energy Qdof (115.2±1.3) kJ/mol is obtained subsequently. Taking the retrogression treatment schedule of 190 °C, 45 min derived from AA7055 thin plate as reference, the non-isothermal retrogression modelfor GBP coarseningbehavior is established based on “LSW” theory and “iso-kinetics” solution, which includes an Arrhenius form equation. After that, the average size of GBP r(t) is predicted successfully at any non-isothermal process T(t) when the initial size of GBP r0 is given. Finally, the universalcharacterization method for the microstructure homogeneity along the thickness direction of 7A55 aluminum alloy thick plate is also set up.
Key words: non-isothermality; retrogression kinetic; 7A55 aluminum alloy; grain boundary precipitate
