Lamellar orientation control of directionally solidified Ti–46Al–0·5W–0·5Si alloy by self-seeding technology

Abstract

Lamellar structures of Ti–46Al–0·5W–0·5Si (at-) alloy solidifying through the primary α phase were successfully aligned parallel to the growth direction using a self-seeding technology in a Bridgman type directional solidification furnace. At the growth rate of 20 μm s−1 and temperature gradient of 12·1 K mm−1, the α phase grows along the [Formula: see text] direction. Therefore, the parallel lamellar structures, whose lamellar orientation is [Formula: see text] direction, can grow continuously until the end of solidification under these solidification parameters. The original lamellar structures of the unmelted region parallel to the growth direction and suitable solidification parameters are necessary for TiAl alloys solidifying through the primary α phase to control the lamellar orientation. The self-seeding technology gets rid of the cutting and fixing of seeds and simplifies the processing of controlling the lamellar orientation of TiAl alloys. It can promote the engineering applications of the lamellar orientation control of TiAl alloys.

Review on Progress of Lamellar Orientation Control in Directionally Solidified TiAl Alloys

“…For a specific composition Ti-46Al-0.5W-0.5Si, a cut sample was directly used for DS, and the bottom of the sample acted as a seed; the schematic is shown in Figure 2 [ 33 ]. The growth principle of the seed crystal part is similar to that proposed by Kim et al [ 34 ].…”

“… Schematic diagram of preparing specimens for lamellar orientation control by self-seeding method (SST) [ 33 ]. ( a ) structures of master ingot, ( b ) structures of seeding specimen, ( c ) solidification processing of SST.…”

Effect of lamellae orientation on tensile properties of directionally solidified Ti–46Al–0.5W–0.5Si alloy

“…The growth length of the samples was 100 mm during the directionally solidification process. The self-seeding method was used to control the lamellar orientation of the TiAl alloys, and the details of experimental methods were described in references [35,36]. The solidification parameters to prepare DS Ti-46Al-0.5W-0.5Si (at.-%) alloys with different lamellae orientation were selected according to reference [36], as shown in Table 1.…”

Microstructure evolution and interfacial reaction of TiAl–Si alloy solidified in alumina crucible

“…14,[17][18][19] Controlled lamellar structures can be acquired by directional solidification with the help of seeding technology, and several TiAl alloys were realized lamellar orientation control by this method. [18][19][20][21][22][23][24][25] For the lamellar orientation control processing, the Ti-43Al-3Si (at-%) alloy is used as a applicable seed material due to lamellar orientation could be retained during remelting and solidification processing. 18,19 Several studies have focused on the microstructures of TiAl-Si alloys solidified in metal mould or without crucibles.…”