The creep characteristics of Sn—5 wt% Bi alloy have been investigated under different constant applied stresses ranging from 26.8 to 29.4 MPa and at different temperatures ranging from 305 to 373 K. Results of both transient and steady state creep indicated one transition point at 328 K. The transient creep parameters β and n were calculated and found to change with the applied stresses from 1.8 × 10−6 to 6.36 × 10−5 and from 0.53 to 0.98, respectively. The strain rate sensitivity parameter (m) was found to change from 0.071 to 0.093 which characterizes a dislocation mechanism. The activation energy of the transient creep amounted to 17 and 33 kJ/mol before and after the transformation temperature, due to both glide of dislocations and cross slipping dislocation mechanism, respectively. The activation energies of the steady state creep in the vicinity of the transformation and above the transformation temperature were found to be 62 and 87 kJ/mol as characteristic of the grain boundary sliding mechanism. The analysis of the X‐ray diffraction patterns of the alloy samples confirmed all the above‐mentioned mechanisms.

The effect of plastic deformation on the microstructure of heat treated superplastic alloy samples (Sn–5wt% Bi) prepared at two different rates of cooling 1.77 × 10–3 K/s and 18.4 K/s, named as slowly cooled and quenched in liquid nitrogen samples, have been studied as a function of temperature in the range of 308–388 K. The work hardening parameters for the two alloy samples were found to be dependent on both temperature and cooling rate. These parameters indicate the transition temperature at 328 K. The slowly cooled samples are much harder than those quenched in liquid nitrogen. This is explained by precipitation of Bi‐atoms which segregate to form a non‐coherent cubic α‐phase in the slowly cooled samples. The activation energy for fracture of the Sn–5wt% Bi alloy is divided into three stages with values of 19.2 ± 1.6, 18.7 ± 1.4 and 10.9 ± 0.81 kJ/mol and 15.6 ± 1.9, 14.6 ± 1.8 and 7.9 ± 1.1 kJ/mol for the slowly cooled and quenched alloy samples, respectively. The lattice parameters (a, c), the ratio (c/a) and the residual lattice strains (Δa/a, Δc/c) are found to be dependent on the test temperature and the rate of cooling with either maximum or minimum values at the transition temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The microstructure and micro-hardness of Sn-3.5wt.5%Ag, Sn-3.5wt.%Ag-0.27wt.%Ti and Sn-3.5wt.%Ag-0.27wt.%Cd treated at 75, 100, 125 and 150oC were studied. The microstructure characteristics of the tested alloys had been investigated using optical microscope (OM), scanning electron microscope (SEM) and x-ray diffraction (XRD). The impression creep had been carried out using Vickers micro-hardness indenter under different loads (10, 50 and 100gm). The stress exponent values were found to be varied from 3.2 to 8.4. The energy activating the creep processes support dislocation climb as the rate controlling mechanism. The dislocation mobility was restricted due to the agglomerations of the Ag3Sn eutectic phase in the above three solders. Whereas; the presence of the twinning of ?-Sn phase, and the dispersion of fine CdSn1.9 IMCs throughout Sn-3.5wt.%Ag-0.27wt.%Cd made strongly blockage of the dislocation motion.

Eutectic (Sn-3.5wt.%Ag) solder alloy is used in electronic circuits in which the creep property of the solder joints is essential for their applications. The study of creep, structure and thermal properties of three solder alloys (Sn-3.5wt.%Ag,Sn-3.5wt.%Ag-0.27wt.%Ti and Sn-3.5wt.Ag-0.27wt.%Cd) is characterized by the presence of (Ag3Sn-IMC) beside the phase (β-Sn). The microstructure parameters obtained from the X-ray analysis represented by, lattice parameters (a, c), the axial ratio (c/a), the residual strains (Δa/a0, Δc/c0) and peak height intensities (hkl) of some crystallographic planes are given. All parameters were found to be sensitive to the additions of (Ti or Cd), applied stresses and working temperatures in the range (298-373K).The crystallite size of the (211) reflection was found to increase from (61-132nm) with the additions and to decrease from (115-79nm) with the working temperatures. The morphological studies show a remarkable decrease in the size of (β-Sn) grains with the addition of (Cd) content which confirms the X-ray data. The obtained results show a decrease in melting temperature with the additions. The creep properties are notably improved by the addition of either (Ti) or (Cd). In order to reveal the creep characteristics such as stress exponent (n) and activation energy (Q), the tensile creep tests were performed within the temperature range (298-373K) at constant applied stress (17.27MPa). Based on the obtained stress exponents and activation energies, it is explained that the dominant deformation mechanism is dislocation climb over all temperature range.

Particle strengthening was studied in Sn-xSb (x=0.5–3.0 wt. %). Tensile deformation behavior of Sn-2.5 wt.% Sb is investigated at temperature ranging (298 - 343K) and under different constant loads ranging (5.1 - 14.0 MPa). The microstructure characteristics of the tested alloys have been obtained using x-ray diffraction. Morphological studies using optical microscope have been investigated to obtain correlation between the microstructure and mechanical behavior of the alloys. The improved strength is attributed to the uniform distribution of the SnSb intermetallic compound (IMC) inside b-Sn matrix. Based on the obtained stress exponent (n) and activation energy (Q), it is proposed that the dominant deformation mechanism is dislocation climb over the whole temperature range used.