A high-Nb TiAl alloy with highly refined microstructure and excellent mechanical properties fabricated by electromagnetic continuous casting

Abstract

Male, born in 1968, Ph.D, Professor. His main research fields include solidification and microstructure control, investment casting technology of titanium-aluminum alloys and directionally solidified titanium-aluminum alloys. [1] .Therefore, the development of such a material system has important implications for aeronautics and astronautics fields. However, poor ductility at room temperature as well as low workability at elevated temperatures of the high-Nb TiAl alloys restricts their applications [2] . According to current knowledge, high mechanical properties can be achieved in these materials by attaining a finer fully lamellar microstructure [3] . Electromagnetic continuous casting (EMCC) is a technique which is in virtue of electromagnetic force to strengthen the movement of the metallic melt and improve heat transfer during solidification. When the EMCC is applied to the melt during solidification, the Abstract: In the present research, microstructure refinement of a high-Nb TiAl alloy (Ti-48Al-8Nb-0.15B ) was realized by means of the electromagnetic continuous casting (EMCC) technique. The microstructure of an ingot obtained by EMCC was analyzed using scanning electron microscopy (SEM). As compared with the raw as-cast alloy, the obtained EMCC alloy presented a much finer microstructure with lamellar colonies with a mean size of about 50-70 μm because the electromagnetic stirring broke initial dendrites and enhanced the heterogeneous nucleation. As the grains were refined, the properties of the TiAl alloy were improved significantly. This implies that the EMCC technique could offer the possibility of application for high-Nb TiAl alloys with a refined microstructure and excellent properties to be used as a structural material. microstructure would be refined and the distribution of compositions also could be homogenized [4][5][6] . EMCC technique has been applied to the production of many alloys such as aluminum alloys [4] , magnesium alloys [5] and alloyed steels [6] , but application to TiAl alloys has rarely been reported. Based on the above opinions, the EMCC technique was used in refining a high-Nb TiAl alloy with the composition of Ti-48Al-8Nb-0.15B in the present study, and the microstructure and mechanical properties of EMCCed samples were investigated.

Effect of heat treatment and thermomechanical processing on microstructure and tensile property of Ti-44Al-8Nb-0.2W-0.2B-0.5Y alloy

“…At high temperature, β phase can provide more slip systems, which can significantly improve the thermoforming ability of TiAl alloy. As a widely used β phase stabilized element, Nb could improve the strength, creep resistance and high temperature oxidation resistance of TiAl alloys, so high Nb-TiAl alloys with good thermoforming ability have been a hot research area in recent years [13][14][15][16][17] . According to the phase diagrams of TiAl alloys containing Nb [18] , the addition of Nb could decrease α phase transition temperature and enlarge β phase region significantly.…”

Effect of Cr on microstructure and oxidation behavior of TiAl-based alloy with high Nb

“…Compared with nickel-based superalloy, which has been widely used for more than fifty years, TiAl alloy containing high Nb is lighter in weight. The high Nb TiAl alloy exhibits superior creep properties and high temperature oxidation resistance compared to normal TiAl based alloy over 973 K [1][2][3][4][5][6][7][8][9] .…”