| The low density, high strength and can maintain high strength and oxidation resistance and good burning resistance and other excellent characteristics in high temperature service environment, which make it to be an important lightweight structural materials at high temperature in aerospace and automotive industries. Therefore speed up the development of TiAl lightweight high-temperature structural materials has important significance. But the low room-temperature ductility of TiAl alloy is an important bottleneck to limit its engineering application. In this paper, the canned-forging was used to refine the as cast microstructure, so as to improve the performance of the material.A size of Φ110mm × 150 mm TiAl alloy ingot with nominal composition of Ti-47Al-Cr-2Mn-0.5Fe-0.05 Y alloy(at.%)with coarse grain of near-γ was prepared by introduction skull melting, and the actual composition of the alloy is Ti-47.64Al-0.99Cr-1.31Mn-0.51Fe-0.02 Y. Thermal compression experiments was carried out on Gleeble-1500 D type thermal simulation test machine for casting alloy materials, and the hot compression temperature was between 1050℃ and 1250℃; strain rate ranged from 0.01s-1 to 0.5s-1and the deformation was 70%.The value of the thermal activation energy was 352.36KJ/mol of the cast alloy material, and established the constitutive equation; drew the power dissipation map, rheological instability map and hot processing map at ture strainε=0.2. The microstructure evolution of the alloy during hot deformation was analyzed, and the appropriate thermal process was obtained. The temperature is between 1180℃ to 1250℃, and the strain rate between is 0.05 s-1 to 0.1s-1.According to the results of the thermal simulation experiments, a small size of Φ40×60mm cylindrical sample ingot was canned forging in the way of second forgoing. The experiment set the total high temperature deformation to 70%, 75% and 80%, respectively, the microstructure and properties of the forging cake with different total deformation were analyzed. The results of XRD BSE and EBSD analysis indicated that the forged Ti-47Al-Cr-2Mn-0.5Fe-0.05 Y alloy is a near gamma microstructure, and the grains are obviously refined. The results of room temperature tensile test showed that the larger the deformation was, the greater the tensile strength of the alloy was. The tensile strength of the forged alloy with a total deformation of 80% is 415.60 Mpa and 523.33 Mpa at 750 and 800, respectively, and the elongation is 35% and 37.8%, respectively; the alloy material has the phenomenon of abnormal temperature yield.The fracture mechanism of the alloy was analyzed. The fracture toughness test of the forged alloy with 80% deformation was carried out at room temperature and fracture toughness value is KIC=13.89 MPa·m1/2.In this paper, the heat treatment experiment was carried out to study the microstructure evolution of the forged Ti-47Al-Cr-2Mn-0.5Fe-0.05 Y alloy specimen with a total deformation of 80%, experiment showed that the thermal treatment of holding time on the microstructure in the heart of the specimen has an important influence, and the microstructure of duplex structure and the full lamellar were obtained at 1410℃ keeping 20 min and 1430℃ keeping 30 min, respectively. The results of EBSD analysis showed that the volume fraction of the alpha 2 phase in the full lamellar structure was 10.27%. |
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