| Ti Al alloy has the advantages of low density, high specific strength, high temperature creep resistance and high temperature oxidation resistance, is considered to be the most promising intermetallic compound material. However, Ti Al alloy’s intrinsic brittleness, low toughness, and plasticity at room temperature and, associated to the poor formability, making it difficult to process. This feature has become a major obstacle to hinder its further development. Therefore, it has become a hot research topic to explore the processing technology of Ti Al alloy.Selecting experimental materials as Ti-48Al-2Cr-2Nb and Ti-48Al-2Cr-2Nb-0.8Er, using the water-cooled copper crucible directional solidification apparatus to execute directional solidification experiments of Ti Al based alloy, in solidification process, adding pulse current with different current density and frequency, to study the effect of pulse current on Microstructure and mechanical properties of Ti Al based alloy.The macro structure of Ti-48Al-2Cr-2Nb-(0.8Er) alloy under the action of pulse current was studied. Analyzing the orientation region of the alloy, the angle between the grain and the growth direction. The results show that for Ti-48Al-2Cr-2Nb alloy, the pulse current frequency is 100 Hz and the current density is from 0 to 84.9 m A/mm2. With the increase of pulse current density, continuity of columnar crystals gradually improved while grain deflection angle decreases, and then increases. When the current density is 56.5 m A/mm2, the minimum angle is reached. When the pulse current density is 56.5 m A/mm2, the frequency is from 0 to 100 Hz, with the increase of the pulse frequency, the continuous enhancement of the Ti-48Al-2Cr-2Nb alloy columnar crystal, the grain deflection angle becomes smaller. With the increase of frequency, continuity of Ti-48Al-2Cr-2Nb-0.8Er alloys gets worse, and grain deflection angle becomes larger.The microstructure of Ti-48Al-2Cr-2Nb-(0.8Er) alloy under the action of pulse current was studied. Analyzing the columnar grain spacing, the interlamellar spacing and the angle of the lamellar. With the increase of the pulse current density, the columnar crystal width of the stable growth zone and the interlamellar spacing first decreases and then increases, and the orientation of the lamellar increases gradually. With the increase of the pulse frequency, the columnar grain width and the interlamellar spacing are decreased. For Ti-48Al-2Cr-2Nb-0.8Er alloy, with the increase of the frequency of the pulse current, the columnar grain width and the interlamellar spacing are gradually reduced. Compared with Ti-48Al-2Cr-2Nb, the grain size and the interlamellar spacing of Ti-48Al-2Cr-2Nb-0.8Er under the action of pulse current have not been refined obviously, and the angle of lamellar decreases.Microhardness, compression test and fracture test of Ti-48Al-2Cr-2Nb alloy and Ti-48Al-2Cr-2Nb-0.8Er alloy are done respectively. The microhardness, compressive strength and fracture toughness of Ti-48Al-2Cr-2Nb alloy first increased and then decreased with the increase of current density, and the maximum value was obtained at the current density of 56.5 m A/mm2. With the increase of the frequency of pulse current, the micro hardness, compressive strength and fracture toughness of Ti Al based alloy are improved. The micro hardness, compressive strength and fracture toughness of Ti-48Al-2Cr-2Nb and Ti-48Al-2Cr-2Nb-0.8Er are directly proportional to the interlamellar spacing d-0.5. As Ti-48Al-2Cr-2Nb alloy, when the pulse current was 56.5 m A / mm2, the frequency is 100 Hz, it achieves the best overall performance, micro hardness value of 377.06, compressive strength is 2093.25 MPa, compression deformation amount was 31.89%, the fracture toughness of 22.965 MPa?m1/2.Compared with Ti-48Al-2Cr-2Nb, the microhardness and compressive strength of Ti-48Al-2Cr-2Nb-0.8Er are improved, and the fracture toughness is decreased. And Er’s addition did not increase reinforcement effect of the interlamellar spacing, Er’s strengthening effect is as the second phase. The addition of Er makes the compression deformation of Ti Al based alloy decrease. As Ti-48Al-2Cr-2Nb-0.8Er alloy, when the pulse current was 56.5 m A / mm2, frequency 150 Hz, it achieves the best overall performance, micro hardness value of 397.85, compressive strength is 2087.19 MPa, compression deformation amount to 36.95%, the fracture toughness of 22.090 MPa?m1/2.Research of graphite sleeve’s effect of Ti-48Al-2Cr-2Nb alloy’s microstructure and properties is studied. It is found that addition of graphite sleeve gets the success rate increase, but continuity of orientation structure variation, deviation angle becomes larger, the grain and the lamellar somewhat coarsening, sheet offset angle becomes smaller. After addition of graphite, the hardness, compression index and fracture toughness of the material were decreased. |
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