SANS investigations on the solidification of aluminum alloys

Small-angle neutron scattering (SANS) measurements have been carried out on pure Al and on Al-0.3Ti-0.02B (wt%) alloy during solidification with different cooling rates. The experimental data have been fitted to the Porod law (dΣ/dΩ)(Q)=KpQ-4, where the increase in Porod constant Kp during solidification is expected to be proportional to the specific surface SV of the grain boundaries. For increasing cooling rates the specific surface of the grain boundaries is found to increase for both samples, indicating a decrease in grain size. The presence of TiB2 grain refiners in the Al-0.3Ti-0.02B alloy further reduces the grain size compared to pure aluminum at a given cooling rate