Cost-Effective TiAl based Materials
Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex chunky parts of TiAl for various advanced applications including aerospace and automotive industries.
Solidification behavior of Ti5Si3 whiskers in TiAl alloys
Abstract The solidification behavior of Ti 52 Al 48 – x Si ( x =0, 0.5, 1.0, 2.0, 3.0, 6.0 at.%), Ti 52 Al 48 –3Si2M (M=Cr, V) and Ti 52 Al 48 –3Si2Cr2V at.% alloys has been studied using differential thermal analysis (DTA) and microstructure examination. The Ti 5 Si 3 phase was formed during solidification of the Si containing TiAl alloys. Two types of Ti 5 Si 3 phase were found in Ti 52 Al 48 – x Si ( x =0.5, 1.0, 2.0 at.%). The first one was formed during the L→Ti 5 Si 3 +L 1 transformation as large isolated Ti 5 Si 3 whiskers formed before primary solidification, and the second one was characterized by whiskers in a eutectic morphology resulting from the solidification of L 2 →α+Ti 5 Si 3 after the primary solidification of L 1 →β+L 2 . In contrast, the primary solidification in the Ti 52 Al 48 –3Si alloy was L 1 →α+L 2 , and a third type of Ti 5 Si 3 phase was formed by a eutectoid reaction of α→γ+Ti 5 Si 3 . The effect of Cr and V on the solidification behavior and constituents of the Ti 5 Si 3 phase were studied with distributed coefficient of Cr, V, and Si. The uniform distribution of fine Ti 5 Si 3 whiskers in the Ti 52 Al 48 –3Si2Cr2V alloy gives effective reinforcement of the matrix.
Magnetic properties of Lu2Fe17 crystals
Abstract We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis.