الفهرس 
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Abstract
The present thesis mainly covers studying the effect of structural, due to thermal treatment, on the mechanical properties of Al- 4043 alloy. Three topics are discussed:
1. Studying the effect of both annealing temperature Ta (573, 673 and 773K) and annealing time ta (0.5, 1, 2.5, 5 and 10h) on the microstructure variations and its reflection on stress-strain characteristics of Al- 4043 wire samples tested at constant testing temperature T (300K) and strain rate ε• of 1.2x10-3s-1.
2. Studying the effect of strain rates ε• ranged from 5.4×10-5 to 1.2x10-3s-1 and testing temperatures T in the range of 300 to 573K on stress-strain characteristics of Al- 4043 wire samples annealed for constant Ta and ta (773K and 0.5h).
3. Studying the relaxation behavior of Al-4043 wire samples tested at different (i) ε. And T for constant Ta (773K) and ta (0.5h) (ii) Ta and ta for constant ε. (1.2x10-3s-1) and T (300K). The structural changes accompanying the above effects were carried out using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) investigation.
In the first part, the obtained results showed that the microstructure of Al-4043 alloy is characterized by the presence of spherically shaped Si-particles, which were found to be uniformly distributed within the Al-matrix. Stress-strain characterizations of Al-4043 samples annealed at different temperatures (Ta = 573, 673 and 773 K) for different periods of time (ta = 0.5, 1, 2.5, 5 and 10 h), showed that the work-hardening parameters (yield stress σy0.2, fracture stress σf and total strain Εt) were strongly affected by the variation of Ta and ta. Both σy0.2 and σf were decreased with increasing Ta and/or ta while Εt increased. The tensile properties of Al-4043 alloy mainly depend on the size of Si particles which may change during annealing process. Also, the size and/or coalescence of Si particles were increased with increasing Ta and/or ta while the size of α-Al8Fe2Si and β-Al5FeSi particles was decreased. Attention has been also paid to the role of the existence of Fe, Cu and Ti elements on the structure and tensile response of the alloy under investigation.
In the second part, at higher T and lower ε•, the dynamic recovery occurs resulting in a decrease in work hardening parameter WHP (σy0.2, σf and χp) while Εt increases. The decrease of the WHP may be due to the fine dispersion of the second phase particles of Si. On the other hand, with increasing ε• and/or decreasing T, the WHP (σy0.2, σf and χp) were increased according to the Norton power law σ = Cε˙m, while the total strain Εt was decreased. The strain rate sensitivity index m increases as T increases and this indication the presence of a softening process in Al- 4043 alloy.
In the third part, from the stress relaxation curves for Al- 4043 samples at different ε•, T, Ta and ta, it was found that; the normalized stresses σn decreased with increasing time t. Also the decay in σn with time can be divided into two stages: i) an initial rapid stage of relaxation (stage I) which generally predominates within the first 75sec, and ii) slow stage, which starts immediately after the 1st stage and extends up to about 170 sec. The decay rate k, the power of the time dependence of damping α and were found to be strongly affected by Ta, ta ε•, and T.