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The effect of grain size as well as ageing temperature on the creep charactenstics of A1-10 wt% Zn alloy have been studied. It has been found that the steady state creep rate c decreases by increasing grain size, whereas it increases by increasing ageing temperature. It is suggested that the decrease of c may be due to the change in the density of mobile dislocations in addition to the change in concentration of point defects and impurity atmospheres. An empirical formula E = m l T 2 + c has been proposed to correlate the creep rate and grain size. The values of the activation energies controlling the creep processes corresponded to that required for dislocation glide.

-0.1 wt% Zr-0.1 wt% Ti alloys were used to trace the effect of Zr and Ti additions on the behaviour of the steady state creep. After solid solution treatment specimens of both alloys were aged at 623, 673, 723 and 773 K and creep tests were performed at room temperature by applying stresses of 60.0, 62.4, 64.7 and 67.1 MPa. The results showed a sound stabilization effect of Zr and Ti on the ageing characterstics of binary Al-1 wt% Si alloy. Values of the applied stress sensitivity parameter, m, obtained were in the range of (20-34) for Al-Si alloy and (14-19) for Al-Si-Zr-Ti alloy. Time to rupture was found to be strongly increased by Zr and Ti additions. The activation energies of the precipitation process involved were found to be 81.9 kJ/mole and 33.7 kJ/mole of the Al-Si and Al-Si-Zr-Ti alloys respectively.

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This paper concerns the effect of the two-phase microstructure (solid solution plus SnSb intermetallic) on the creep behaviour of an Sn-10 wt % Sb alloy. The alloy was specially cast and drawn into wires of 0.55 mm diameter. Samples were heat treated at temperatures of 348, 373, 398, 423 and 448 K to produce a range of volume fractions of the intermetallic b-phase SnSb. Constant-load creep tests were carried out at room temperature for each of the wire samples. The results obtained show that there is a relationship between the heat-treatment temperature T a and the microstructure and that this, in turn, affects the creep properties of the alloy. Quantitative scanning electron microscopy (SEM) analysis has been used to determine the relationship between the microstructure and the mechanical behaviour of the alloy independently of any microstructural changes which might occur during creep at more elevated temperatures. It is shown that the steady state creep rate can be described in terms of the mass fraction X Sb of antimony dissolved in the matrix phase, the mean grain size d (mm) and the applied stress | (MPa) by the equation 8.19 , where the strain rate is given in reciprocal seconds. Comparisons are made with other observations on the creep resistance of solder alternatives.