Quaternary Diffusion in the α Solid Solutions of AI-Zn-Mg-Ag Alloys

摘要

Quaternary interdiffusion experiments of Al-rich α Al-Zn-Mg-Ag alloys have been performed in the temperature range from 725 to 832 K. The concentration profiles indicate that the diffusion distance of Ag is shorter than those of Zn and Mg in the solid solutions. The direct interdiffusion coefficients D~4_(ZnZn), D~4_(MgMg) and D~4_(AgAg) are positive, and indirect coefficients are negative. The impurity diffusion coefficients of Ag, Cu or Mg in Al-Zn-Mg (or Ag) alloys can be expressed by the following equations. D~*_(Mg(Al-3.04Zn-1.90Ag)) = 2.0X10~(_5) exp(-119 kJ mol~(-1)/RT~(-1) m~2/s, D~*_(Ag(Al-3.37Zn-2.75Mg)) = 1.9Xl0~(-5)exp(-138 kJ mol~(-1)/RT~(-1)) m~2/s, D~*_(Cu(Al-3.37Zn-2.75Mg)) = 5.7X10~(-5)exp(-132 kJ mol~(-1)/RT~(-1)) m~2/s. The ratio values of indirect to direct diffusion coefficients suggest that attractive interactions of Zn-Mg atoms exist in the Al-Zn-Mg-Ag alloys.