Lanthanum hexaboride as advanced structural refiner/getter in TiAl-based refractory intermetallics

Microstructure and mechanical properties control of γ-TiAl(Nb, Cr, Zr) intermetallic alloy by induction float zone processing

“…As-cast billet had 165 mm in diameter being 15 kg of mass; the details of casting could be found in our paper [8].…”

Grain refinement mechanism in advanced γ-TiAl boron-alloyed structural intermetallics: The direct observation

“…Thus, cooling rate was varied in the range from 1.3 to 3 K·s -1 along an ingot in the course of solidification. More detailed description and schematic of applied cast technique could be found in [2].…”

“…Nb alloying significantly improves high temperature properties of TiAl based alloys, whereas minor additions of Cr and Zr enhance their oxidation resistance within turbine gas flow. Lanthanum addition was applied firstly by us for the internal gettering of undesired oxygen impurity [2]. Generally, finer microstructure provides better performance of an alloy that requires the specific two-phase γ-TiAl+α 2 -Ti 3 Al polycrystalline pattern creation in cast items.…”

Advanced Heat-Resistant TiAl (Nb,Cr,Zr)-Based Intermetallics with the Stabilized β(Ti)-Phase

“…3 Boride ribbons resolved in Ti-44Al-5Nb-2Cr-1.5Zr-0.4B-0.07La (a) and three consecutive stages of structure refining mechanism development: event of solid-state germination (seeding) of a 2 -Ti 3 Al phase on boride facet (b); morphological development of a 2 -laths and their growth through c-TiAl matrix (c); formation of new grain boundary by elongated curved boride surrounded by fine c + a 2 phase structure inside the delimited grains (d). The electron microscopy micrographs [15,16] Figure 4a displays the irregular microstructure of initial virgin ingot of Ti-44Al-5Nb-3Cr-1.5Zr, which was manufactured by semi-continuous electron-beam synthesis/casting technique from the pure metals [14]. Basic phase c-TiAl is imaged here by gray, a 2 -Ti 3 Al-by black and B2-as bright phase.…”