M. M. Mostafa

Stress enhanced diffusion process in Al-10 wt.% Zn alloy

The change in the steady state creep of Al-10 wt. % Zn alloy was studied under various constant stresses ranging from 77 MPa to 88·3 MPa and at different constant temperatures ranging from 423 K to 483 K. The strain rate sensitivity parameter (m) varied between 0·15 to (0·4 ± 0·05) in the above temperature range. The energy activating the steady state creep amounted to 70·3 kJ/mole in the temperature range from 423 K to 443 K and to 124·3 kJ/mole in the temperature range from 453 K to 483 K characterizing the grain boundary diffusion of Zn in B-phase and Al inα-phase, respectively. This was affected by increasing the applied stress. The decrease in the activation energy was attributed to the stress enhanced diffusion processes. Microstructural analysis confirmed that the above mentioned mechanisms took place during steady state creep.

Microstructure dependence of yielding and fracture in Cd-Zn alloys

The coefficient of logarithmic work-hardening, the yield stress and the fracture stress of Cd-2 wt. %Zn alloy of different grain diameters and of Cd-17·4 wt. %Zn alloy decrease with increasing working temperature. Two relaxation temperature regions have been found, the low-temperature region of relaxation (below 483 K) and the high-temperature region (above 483 K). The fracture surface energy for Cd-2 wt. % Zn alloy has been calculated and found to be 1·2 J/m2 at the two temperature regions of relaxation. X-ray investigations show that the residual internal strains in the deformed samples increase with increasing working temperature and exhibit a peak value at 483 K.

Microstructure dependence of steady state creep in Cd–Sn eutectic alloy

The steady state creep of Sn–33 wt.% Cd alloy was studied under various constant stresses ranging from 25.56 to 30.85 MPa in the temperature range from 353 to 433 K. The stress exponent n was found to change from 6.25 to 4.55 in the above temperature range. The energy activating the steady state creep amounted to 59.3kJ/mol in the temperature range from 353 K to 393 K and to 37 kJ/mol in the temperature range from 413 K to 433 K characterizing the grain boundary diffusion in Cd and in Sn, respectively. Microstructure analysis confirmed that the above mentioned mechanisms took place during steady state creep.

Transient creep during transformation in Cd-Zn alloys

AbstractTransient creep of Cd-2 wt. % Zn and Cd-17·4 wt. % Zn alloys has been studied under different constant stresses ranging from 6·4 MPa to 12·7 MPa near the transformation temperature. The results of both compositions showed two transient deformation regions, the low temperature region (below 483 K) and the high temperature region (above 483 K). From the transient creep described by the equationɛtr=Btn, whereɛtr andt are the transient creep strain and time. The parametersB andn were calculated. The parameterB was found to change with the applied stress from 0·3×10−4 to 3×10−4 and from 0·6×10−4 to 18×10−4 for Cd-2 wt. % Zn and Cd-17·4 wt. % Zn, respectively. The exponentn was found to change from 0·8 to 0·95 for both alloys. The parameterB was related to the steady state creep rate

Phase characteristics of pre‐deformed Al–40 wt% Zn alloy

\dot \varepsilon _{st}

Steady state creep during transformation in Al–1 wt.%Cu alloy

through the equation

Enhanced creep parameters of Al–Zn alloy induced by cyclic stress reduction

B = B_0 \dot \varepsilon _{st}^\gamma