TG6合金等温变形条件下组织演变与性能的研究

Microstructure Evolution and Properties of TG6 Alloy under the Isothermal Deformation Condition

摘要:

采用不同的等温锻造火次和相同的总变形量，改变TG6合金锻件的加热时间和每火次变形量，对该合金等温锻件的显微组织演化与拉伸性能进行研究。结果表明：随等温锻造火次增多，组织中初生α相含量增多，片状次生α相长度和亚β晶粒尺寸先减小后增大，而片状α相的厚度递增。室温和高温拉伸强度随锻造火次的增加呈现先减少后增加的趋势，塑性则先增加后减小。1火次成形时变形量较大，锻件产生温升造成组织中初生α相较少，同时较多且细长的次生α相增加了该锻件的拉伸强度。3火次成形时由于合金中各相再结晶程度不同，使组织中亚β晶界处产生较多细小等轴α相，该相增加了锻件的塑性。5火次锻造时，锻件加热时间较长，造成组织中α相的聚集长大。TG6合金等温锻造多火次成形时，每火次变形量存在一临界范围，处于该范围内每火次锻后空冷时合金发生部分再结晶，形成较为细小的等轴α相，阻碍亚β晶界的迁移，致使亚β晶粒尺寸较小，同时也造成组织中等轴α相尺寸的不均匀

Abstract:

The microstructure evolution and tensile properties of the isothermally forged TG6 alloy were studied with different heating time and different deformation degrees of each forging by means of different isothermal forging times and the same total deformation degree. The results indicate that with increasing of isothermal forging times, the content of primary α phases increases, the length of lamellar secondary α phases and the size of sub-β grains decrease at first and then increase, and the thickness of lamellar secondary α phases increases progressively. At room temperature and high temperature the tensile strength of the forging decreases firstly and then increases while the ductility changes on the contrary. For the one-time forging formation with high deformation degree, there are fewer primary α phases in the microstructure caused by temperature rise in the forging; meanwhile more secondary α phases which are long and thin increase the tensile strength of the forging. For the three-time forging formation, more α phases which are fine and equiaxed occur at the sub-β grain boundaries because of different recrystallization degree of every phase in the alloy, leading to the increased ductility of the forging. For five-time forging, the prolonged heating time of the forging results in the aggregation and growth of α phases in the microstructure. When the TG6 alloy is isothermally forged with multi-times formation, there is a critical range for each-forging deformation degree; in the range, partial recrystallization takes place for the forged alloy during air cooling to form fine equiaxed α phases, which restrict the transfer of sub-β grain boundaries, resulting in the small sub-β grain sizes and uneven equiaxed α phase sizes in the microstructure