硼变质激光熔化沉积TC4的低周疲劳性能

Low-Cycle Fatigue Performance of Boron-Modified TC4 Deposited by Laser Melting

研究了激光熔化沉积硼变质TC4钛合金材料在不同应变幅值下的低周疲劳性能。结果表明,激光熔化沉积硼变质TC4样件在0.8%~1.0%应变幅值下的低周疲劳性能与退火态锻件相当。通过对比分析固溶时效态激光熔化沉积硼变质TC4与退火态TC4锻件的微观组织、低周疲劳性能可以发现,当经受高于1.0%的应变幅值时,固溶时效态激光熔化沉积硼变质TC4的网篮组织比TC4退火态锻件的双态组织具有更好的抵抗裂纹扩展的能力。此外,固溶时效态激光熔化沉积硼变质TC4钛合金在各种应变幅值下均发生了不同程度的循环软化行为。最后采用扫描电镜对固溶时效态激光熔化沉积硼变质TC4钛合金的低周疲劳断口形貌进行了观察,并研究了低周疲劳失效过程中裂纹的扩展过程。

This paper investigates the low-cycle fatigue performance of boron-modified TC4 titanium alloy deposited via laser melting at different strain amplitudes. The results reveal that the low-cycle fatigue performance of boron-modified TC4 titanium alloy deposited via laser melting is comparable to that of annealed forging when subjected to a strain amplitude of 0.8%--1.0%. A comparison of the microstructure and low-cycle fatigue performance of the boron-modified laser melting deposited TC4 in solid solution-aging state with the annealed TC4 forging is performed. It is found that as the strain amplitude is above 1.0%, the basket-shaped microstructure of the solid solution-aged boron-modified TC4 titanium alloy deposited via laser melting exhibits better resistance to crack propagation compared with the double phase microstructure of TC4 annealed forgings. Moreover, the solid solution-aged boron-modified TC4 titanium alloy obtained via laser melting deposition exhibits different degrees of cyclic softening behavior at different strain amplitudes. Finally, the morphologies of the low-cycle fatigue fractures of solid solution-aged boron-modified TC4 titanium alloy obtained via laser melting deposition are observed under a scanning electron microscope, and crack propagation during low-cycle fatigue failure is studied here.