Novel technique for grain refinement in aluminum casting by Al–Ti–B powder injection

This paper purposes a novel technique for grain refinement in Al casting by Al–Ti–B powder injection into molten Al. Al–Ti–B powders were made by soaking ribbons, obtained from drilling an Al–Ti–B grain refiner bar, in liquid nitrogen before grinding them into small powders. A simple device for this technique comprises a small hopper to store Al–Ti–B powders, a ball valve to control the release of the powders, and a hose to connect argon to purge all powders into the melt. This novel grain refinement technique provides higher efficiency and a shorter critical contact time, which are believed to be the reasons of smaller fractured TiAl3 and TiB2 particles and higher number of nucleation sites. In addition, the particles can be well distributed throughout the melt with the help of argon purging and act as heterogeneous nucleation sites.