Transformation characteristics of Al-Ag and Al-Ag-Ti alloys

The effect of structure transformations on the stress-strain characteristics of Al-10 wt%Ag and Al-10 wt%Ag-0.2 wt%Ti alloys has been studied in the temperature range from 503 to 573 K for both quenched and slowly cooled specimens. The coefficient of work-hardening, chi = partial derivative sigma(2)/partial derivative epsilon (as Mott's model); the fracture time, t(f); yield stress, sigma(y); fracture stress, sigma(f); Young's modulus, Y, decreased with increasing aging temperature (T-a) and exhibited an abrupt increase at about 543 K. On the other hand, for each curve the fracture strain, sf, and the strain hardening exponent, n, increased with increasing aging temperature and exhibited minimum at about 543 K. The Ti-free samples were generally harder than the ternary samples. It was found that the addition of Ti to Al-10 wt%Ag alloy accelerates the precipitations of gamma' and gamma-precipitates. The activation energy of the fracture mechanism in both alloys was around 25 +/- 0.4 and 51.7 +/- 0.4 kJ/mol before and after transformation, respectively. The microstructure of the samples studied was investigated by transmission electron microscopy (TEM). (c) 2007 Elsevier B.V. All rights reserved.