Predicting the Quality of Grain Refiners from Electrical Resistance Measurements of Aluminum

The objective of grain refining is to reduce the size of the primary solidified crystal grains in aluminum alloys, thereby eliminating large columnar grains. Excellent grain refining results can be achieved only when the grain refining agent is of excellent quality, i.e., the number of Al3Ti and TiB2 particles must be appropriate, the shape and size distribution of the particles must be suitable, the Ti/B ratio must be appropriate, and so on. To evaluate the quality of grain refiners, the electric resistivity was measured on four different grain refiners. The obtained results were supported by differential scanning calorimetry analyses and microstructure analyses. It was found that the quality of a grain refiner can be assessed by measurements of electrical resistance. The lowest electrical resistivity was measured for grain refiner B (Al-3Ti-1B), which had the lowest impurity content and the most suitable number and size distribution of TiB2 and Al3Ti particles, as well as the most optimal Ti/B ratio, namely, 3.6. A larger number and size of TiB2 and Al3Ti particles, as well as elements such as Fe and Si, and also inclusions, which were also confirmed by DSC analyses, cause a higher electrical resistivity due to a stronger scattering of electrons through the matrix.