A.M. Abd El-Khalek

Aging Characteristics of Rapidly Solidified Al–20 wt% Zn Alloy

Al-20 wt% Zn samples were obtained at room temperature by rapid cooling from the melt. The quenched samples were aged at different temperatures below and above the transformation temperature (503 K) for 2 h, then quenched to room temperature. Structure variations and changes in internal friction, thermal diffusivity, Youngs modulus and resistivity were traced for these testing conditions. The different results were explained in terms of the thermally induced structures in the alloy.

Effect of grain size and indium addition on tensile characteristics of Al–1Si alloy

AbstractThe effect of grain size and indium addition on the workhardening characteristics of Al–1Si (wt-%) alloy has been investigated at room temperature (RT). The samples were preaged at different temperatures in the range 523–623 K. The yield stress, the fracture stress, the fracture time and the linear workhardening coefficient generally decreased with increasing temperature and/or grain size, while the fracture strain and dislocation slip distance increased. The yield and fracture stresses for different grain sizes at different temperatures were found to be linearly related to grain diameters. Indium addition caused general increase for all the measured strength parameters. As concluded from transmission electron microscope (TEM) investigations, In addition to Al–Si alloy may retard the coarsening of Si particles. The energies activating the operating fracture mechanisms were found to be 79·6±0·4 and 32·4±0·4 kJ mol−1 for alloys Al–1Si and Al–1Si–0·2In respectively. This suggests a value of 47·2 kJ m...Abstract The effect of grain size and indium addition on the workhardening characteristics of Al–1Si (wt-%) alloy has been investigated at room temperature (RT). The samples were preaged at different temperatures in the range 523–623 K. The yield stress, the fracture stress, the fracture time and the linear workhardening coefficient generally decreased with increasing temperature and/or grain size, while the fracture strain and dislocation slip distance increased. The yield and fracture stresses for different grain sizes at different temperatures were found to be linearly related to grain diameters. Indium addition caused general increase for all the measured strength parameters. As concluded from transmission electron microscope (TEM) investigations, In addition to Al–Si alloy may retard the coarsening of Si particles. The energies activating the operating fracture mechanisms were found to be 79·6±0·4 and 32·4±0·4 kJ mol−1 for alloys Al–1Si and Al–1Si–0·2In respectively. This suggests a value of 47·2 kJ mol−1 as a binding energy between Si and In atoms in Al matrix.

Effect of phase transformation and indium addition on workhardening characteristics of Al-Zn alloy

Abstract Tensile characteristics of both Al–10Zn and Al–10Zn–0·2In (wt-%) alloys were investigated in the temperature range from 413 to 473 K. The workhardening coefficient, the yield stress, the fracture stress, resilience, toughness and fracture time generally decrease with increasing deformation temperature. On the other hand, the fracture strain and dislocation slip distance increased with increasing deformation temperature. The two observed temperature regions around the transformation temperature (443 K), which characterise the magnitude of variation of these parameters point to two fracture mechanisms activated with 23·2 and 49·4 kJ mol−1 for the low and high temperature regions respectively. Indium addition caused general increase for all the measured strength parameters. The microstructures of the samples under investigation have been examined after stress–strain deformation by X-ray diffraction analysis.Tensile characteristics of both Al–10Zn and Al–10Zn–0·2In (wt-%) alloys were investigated in the temperature range from 413 to 473 K. The workhardening coefficient, the yield stress, the fracture stress, resilience, toughness and fracture time generally decrease with increasing deformation temperature. On the other hand, the fracture strain and dislocation slip distance increased with increasing deformation temperature. The two observed temperature regions around the transformation temperature (443 K), which characterise the magnitude of variation of these parameters point to two fracture mechanisms activated with 23·2 and 49·4 kJ mol−1 for the low and high temperature regions respectively. Indium addition caused general increase for all the measured strength parameters. The microstructures of the samples under investigation have been examined after stress–strain deformation by X-ray diffraction analysis.

Effect of ternary addition and γ-irradiation on the characteristics of rapidly solidified Pb-base alloys

The properties of a series of rapidly solidified Pb-Sb 3 -Sn x alloys ( x =0-2.5 r wt.%) irradiated with n -rays were studied. Variations in the internal friction, Q m 1 , thermal diffusivity D th and dynamic Youngs modulus Y were traced before and after irradiation by applying the resonance technique. Variations of specific heat C p were obtained from DTA thermograms. Structure parameters were obtained from the X-rays diffraction patterns. A marked change in the behaviour of the measured parameters was observed at 1.5 r wt.% Sn addition. Besides, irradiation induced defects increased the level of the measured hardening parameters.

Effect of irradiation and pre-ageing temperature on the mechanical properties of Al–Si alloy

Al–1wt.%Si alloy samples in the solid solution state were irradiated with doses of gamma rays up to 1.75 MGy for 2 h in the temperature range from 423 to 553 K. Induced variations in structure, mechanical and electrical properties were traced by suitable techniques. Observed changes in the measured parameters, internal friction Q −1, thermal diffusivity D th, dynamic elastic modulus Y and resistivity, ρ, were explained in terms of the role and mode of interaction of lattice defects in irradiated and thermally treated samples. Composition inhomogeneity and variations in mass distribution in the matrix were also considered. The structure identification of the samples was carried out by using conventional X-ray diffraction techniques and transmission electron microscopy micrographs.

Influence of heat treatment on stress-strain behaviour and lattice parameters of Sn-In alloy

Abstract Sn based alloys have important industrial applications specially as pewters and soldering materials. One of these alloys, Sn–5·2 wt-%In alloy, is designed to be examined in the present work. The differential thermal analysis of this alloy gives a melting temperature value of 493 K. An empirical equation that can be used to determine the melting temperature of some Sn–In alloys is derived. Two different heat treated groups of samples, slowly cooled and quenched, are prepared. The phases present in these two groups of samples are determined from their X-ray diffraction patterns. The isothermal tensile stress–strain tests of all samples are reported at temperatures between 343 and 403 K. The changes of the work hardening parameters and also of the lattice parameters of the β-Sn phase with the deformation temperature are discussed. The values of the activation energy characterise a dislocation fracture mechanism.