EFFECT OF Cu ON PRECIPITATION AND STRUCTURAL PARAMETERS OF Al-Zn-Mg ALLOY
LIN Zhaoqi; ZHU Jiliang; SUN Guijing; YANG Shengkun (Northeast Institute of Technology; Shenyang) (Manuscript received 4 March; 1983; revised manuscript 12 July; 1983)
Cite this article:
LIN Zhaoqi; ZHU Jiliang; SUN Guijing; YANG Shengkun (Northeast Institute of Technology; Shenyang) (Manuscript received 4 March; 1983; revised manuscript 12 July; 1983). EFFECT OF Cu ON PRECIPITATION AND STRUCTURAL PARAMETERS OF Al-Zn-Mg ALLOY. Acta Metall Sin, 1984, 20(1): 54-61.
Abstract The effect of a trace of Cu, about 0.19 wt-％, on the precipitation, the critical nucleation temperature, T_c~′, as well as the microstructural parameters of a commercial purity Al-S.0Zn-1.75Mg alloy has been studied by means of hardness test, optical microscopy and TEM. It was resulted that Cu, in contrast to Cr, is an element by which its homogeneous precipitation is promoted, the T_c~′ is raised from 150—160℃ to 170—180℃ and the hardness is increased, but the grain size is not yet refined and the recrystallization is not yet inhibited. Under the experimental condition of 120—200℃ aging, the grain boundary precipitation, the matrix precipitation and the precipitation-free zone of the Cu-contained alloy are minor to that of Cu-free one. All of these alteration may be monotoneous with elongation of aging time and elevation of aging temperature. Thus, it was proposed that the effect of Cu added on the precipitation and the structural parameters may he explained by a nucleation model which a complex cluster of the vacancy-tetrahedron combined with the segregated solute atoms, such as Zn, Mg and Cu, acts as a nucleus of GP zone.
