准β锻造工艺对TC21钛合金大型锻件组织及性能的影响

Influence of quasi-β forging process on microstructure and properties of TC21 titanium alloy large forgings

以TC21钛合金特大规格棒材及其制备的大型锻件为研究对象,采用准β锻造工艺锻造TC21钛合金,分析了3种不同锻造方案对锻件微观组织和力学性能的影响规律。结果表明:TC21钛合金可在相变点以上一定温度采用准β锻造工艺加工,在不同的加热工艺参数下,通过双重退火进行热处理,均可获得较好的冶金组织和力学性能。TC21钛合金在准β锻造过程中,不同的锻造温度和锻造火次均能获得较好的拉伸性能(1100 MPa左右)和断裂韧性(大于90 MPa·m1/2)。在准β锻造过程中,较高的锻造温度有利于获得网篮组织,合金的断裂韧性较高,组织内片层α相存在粗化趋势;较低的准β锻造温度有利于细化微观组织,但锻造后组织中会有少量残余等轴α相存在。在锻造变形量相同的情况下,较少锻造火次可以获得更加细小的微观组织,但锻件不同部位的微观组织形态存在差异。

For the TC21 titanium alloy oversized bar and the large forgings manufactured by it,TC21 titanium alloy was forged by the quasi-β forging process,and the influence laws of three different forging plans on the microstructure and mechanical properties of forgings were analyzed. The results show that the TC21 titanium alloy obtains better metallurgical structure and mechanical properties by quasi-βforging process at a certain temperature above the phase transformation point and under different heating process parameters as well as heat treatment by double annealing. Furthermore,TC21 titanium alloy obtains better tensile performance( about 1100 MPa) and fracture toughness( greater than 90 MPa·m1/2) under different forging temperatures and forging fire times in the quasi-β forging process. In the process of quasi-β forging,the higher forging temperature is conducive to obtain the basket structure,the fracture toughness of alloy is higher,and the lamellar α phase of structure has a tendency to coarsen. However,the lower quasi-β forging temperature is conducive to the refinement of microstructure,but there is a small amount of residual equiaxed α phase in the structure after forging. Under the same amount of forging deformation,the finer microstructure is obtained by less forging fire times,but the microstructure morphologies at different positions of the forgings are different.