In casthouse applications, the control of grain size is essential in maintaining product consistency and quality, in reducing cost and maintaining high levels of productivity. Controlled addition of Al-TiB master alloy in aluminum releases nucleating particles that promote equiaxed, fine grained structures in cast alloys, thus redistricting formation of columnar crystals. Al-TiB grain refiner alloy improves homogeneity and allows uniform distribution of alloying elements, reduce porosity and eliminate hot tearing in cast structures, improves responsiveness to subsequent heat treatment and enhance mechanical properties and machinability in the fabrication process.
There are two types of particles seen in microstructure of Al-TiB: TiB2 particles – grain refining nuclei – typically 1-2 microns in size, which do not dissolve in liquid aluminum TiAl3 plates / grains – typically 30-60 microns in size, which readily dissolved in liquid aluminum. These particles play an important role in the grain refining process. Typical Al-TiB master alloy micrograph at 100x magnification is clearly showing TiAl3 grain size distribution in aluminum matrix.