화학공학소재연구정보센터
Materials Science Forum, Vol.396-4, 827-832, 2002
Precipitates in a Li-containing Al8.4Zn1.35Mg1.76Cu (wt. %) alloy
The microstructures of 1.0% Li-containing A18.4Zn1.35Mg1.76Cu(wt%) alloy have been studied in this investigation. Specimens were undertaken two-steps aging after solid solution quenching, namely at 120degreesC for 3h followed by 160degreesC for different hours. The response of aging at 160degreesC was studied, which showed that the hardness peak was attained at 9 hours. The microstructure of peak-aged specimen was examined by TEM. The precipitates of this alloy with peak hardness were normally eta'(MgZn2) phases, instead of delta' (Al3Li) phases. However, eta' phases distributed on the matrix were much fine in dimension and more narrow precipitation free zones (PFZs) were observed. The result could probably attribute to the role of Li trapping vacancies, as a consequence the diffusion of Zn and Mg atoms was restrained. No delta '(Al3Li) phase was found both on matrix and at grain boundaries as expected in most Li containing aluminum alloy. The results were discussed with phase diagram and aging kinetics.