Directional solidification of TiAl–Si alloys using a polycrystalline seed

The microstructure parameters and microhardness of directionally solidified Ti–43Al–3Si alloy

“…As was shown in the literature [5,[7][8][9][10], TiAl-based alloys with aligned lamellar orientation have a good combination of strength and ductility in a wide range of temperature. The main challenge is that the lamellar microstructure is not form from the liquid but from the solid-state transformation [5,[7][8][9][10].…”

“…The main challenge is that the lamellar microstructure is not form from the liquid but from the solid-state transformation [5,[7][8][9][10]. During cooling the ␥ phases form from the matrix ␣ phases according to the crystallographic orientation relationship of (1 1 1) ␥ //(0 0 0 1) ␣ .…”

“…Hence, to obtain the preferred lamellar orientation, the orientation of high temperature ␣ phase must first be controlled [8][9][10][11]. However, the aligned lamellar orientation can be obtained by directional solidification and seeding techniques with a seed having specific ␣ orientation [7,9,[11][12][13][14]5]. One of the main factors for this technique is to found a suit seeding materials.…”

“…As a seed material, the primary solidification phase must be ␣ phase and the original lamellar orientation should be restored during heating to and cooling from single-phase ␣-region [8,14]. According to the literature [5,7,9,12,15], Ti-43Al-3Si(at.%) alloy is identified to be a suitable seed material which is used to control the orientation of lamellar structures in TiAl alloys. However, the evolution of microstructure characteristics for Ti-43Al-3Si(at.%) alloy during directional solidification has not been well understood.…”

Solidification behaviour of TiAl-based alloys studied by directional solidification technique

“…10 shows variation of SDAS with the cooling rate according to Eq. (6). Regression analysis of the experimental data for the Tie46Ale8Ta alloy yields an equation for l 2 in the form l 2 ¼ 3:96 Â 10 À5 _ n À0:34 6.…”