Influence of microstructure on grain refining performance of Al–Ti–B master alloys

Abstract

The morphological characteristics of so called duplex titanium aluminide (TiAI 3 ) particles in several AI-5Ti-IB (wt-%) master alloys in the form of rods have been investigated using a wide range of microscopical techniques. It has been found that both rough blocky andfaceted blocky aluminides are present in such materials and that hexagonal platelets are entrained within these blocky aluminides. Auger spectroscopy and transmission electron diffraction have confirmed that the platelets are diborides. In previous work, it has been suggested that duplex aluminides are particularly effective in promoting grain refinement during solidification. To investigate this, a master alloy containing duplex blocky aluminides was briefly remelted and recast from a range of temperatures. This resulted in the formation of significantly different aluminide types. When the original and remelted alloys were tested in commercial purity AI, using standard procedures, it wasfound that the presence of duplex aluminides does not, in itself, seem to be of great importance in influencing grain refiner efficiency. The experimental findings are discussed in the context of previously published experimental and theoretical work.MSTj 1650.

Influence of a Novel Master Alloy Addition on the Grain Refinement of Al-Si Cast Alloys

“…The grain refinement of wrought aluminium alloys relies on the addition of master alloy based on the Al-Ti-B system where a very common used composition is Al-5Ti-1B [6] although other compositions with different titanium to boron ratio [7] or addition of other elements [8] were studied. The main idea of adding master alloys based on the Al-Ti-B system resides on the presence of TiB 2 particles in the melt, which act as sites for heterogeneous nucleation, and Al 3 Ti intermetallics which dissolve into the melt through a peritectic reaction [9][10][11]. Nonetheless, in the case of the Al-Si cast alloys where the silicon content is greater than 3 wt.% the addition of the Al-Ti-B master alloys is not efficient [7] due to the interaction between titanium and silicon (poisoning effect) [12].…”

Influence of Reaction Temperature for the Manufacturing of Al-3Ti and Al-3B Master Alloys and their Grain Refining Efficiency on a Al-7Si Alloy

“…Melt inoculation with titanium and or boron in the form of an aluminium master alloy is the method predominantly used for refining the grain structure. In spite of a vast amount of work in the field of Al grain refinement [8][9][10], the production of master alloys has received very limited attention. The microstructure and performance of a grain refiner, on the other hand are known to be highly sensitive to the processing parameters used in the production of these master alloys [11][12].…”

A Study on the Manufacture of Aluminum Grain Refiner by Flux Reaction

“…The type and size of these particles were mainly affected by the temperature of molten metal and holding time during the production of Al-Ti-B alloy by flux reaction. Studies on the grain refining ability of Al-5wt.%Ti-1wt.%B master alloy, and the effects of process variables during the flux reaction on the microstructure of the master alloy have been widely studied so far, and especially the effect of TiAl 3 phase on grain refinement behavior has been examined by many investigators [3][4][5][6]. However, as the reaction mechanism during the manufacture of Al-Ti-B grain refiner by flux reaction is so complex, significant variations in product performance are reported to be existed.…”