In the present work, Mo was added to an Al–Si–Mg foundry alloy to study its influence on the evolution of dispersoids during various heat treatments. The microhardness and the elevated-temperature tensile properties and creep resistance were measured to evaluate the contribution of dispersoids. Results showed that the addition of Mo greatly promoted the formation of α-dispersoids. During solution treatment, the formation of α-dispersoids started after 8 h at 500 °C. At high temperature (540 °C), the coarsening of dispersoids with increasing time became predominant. The optimum condition of dispersoids can be reached by 520 °C/12 h or 500 °C/4 h + 540 °C/2 h, leading to the highest differences in microhardness between the Mo-containing alloy and base alloy. The tensile strengths were improved at both room temperature and elevated temperatures, while the elongation at elevated temperature was greatly increased. The creep resistance at elevated temperature is further enhanced due to the Mo addition.

Very fine oxide dispersoids have been incorporated into solder alloys to create a new, improved solder structure with an ultrafine grain size of ˜200 -500 nm and significantly enhanced mechanical properties. The microstructure is seen to be quite stable upon high temperature exposure (e.g.. 120°C), which is attributed to the presence of very fine dispersoid particles which impede grain boundary sliding and dislocation movement. As much as three orders of magnitude reduction in the steady state creep rate has been achieved. The new solders also exhibit improved (4–5 times higher) tensile strength at low strain rates and improved ductility under high strain rate deformation. It is demonstrated that with a dispersion of TiO2 particles, the Pb-Sn eutectic solder with a low melting point of 183°C can be made more creep-resistant than the 80Au-2OSn eutectic solder with a much higher melting point of 278°C. The new creep-resistant solders can be useful for optical or optoelectronic packaging in which the dimensional stability of the assembled structure is essential.