Grain refinement of aluminium studied by use of a thermal analytical technique

摘要: Abstract Master alloys based on the system AlTiB are commonly used as grain-refining additives to aluminium castings. It has been shown in previous work that TiB 2 particles most common heterogeneous nucleation sites for crystals. Additions of potent nucleating an melt do not, however, cause grain refinement automatically; there must be a driving force well subsequent growth. The at slow cooling rates can present form constitutional undercooling caused by alloying elements not interact with each other or particles. influence hypoeutectic concentrations silicon and iron hypoperitectic titanium α-Al size studied. is found use two-thermocouple thermal analytical technique from studies microstructure growth-restricting effect Fe, Si Ti additive low concentrations. allows us determine point where dendrites grow together forming continuous network. time lapse impinge calculate average growth rate dendrites. diameter proportional dendrite rate, once equiaxed dendritic completed, final determined. A deterioration occurs high solute Increasing decreases tip radius, counteracting effect. At concentrations, radius eventually critical limit capillary effects start become important increases.