钛铝合金高温-超高周疲劳行为研究OA

As novel lightweight high-temperature structural materials,titanium aluminide alloys exhibit excellent high-temperature strength,oxidation resistance,and creep resistance.It is considered the preferred material to replace nickel-based superalloys.As an elevated-temperature structural component,it is subjected to both elevated temperatures and cyclic loads during service,necessitating research into its fatigue behavior at elevated temperatures.Ultrasonic fatigue testing,an efficient means of fatigue testing,can greatly reduce the time cost of detailed analysis of alloy fatigue failure mechanisms.Accordingly,by combining ultrasonic fatigue testing equipment and a medium high-frequency induction heating device,the cyclic deformation behavior of the Ti-48Al-2Cr-2Nb alloy at 650 ℃ was investigated.The results show that there is no fatigue limit for Ti-48Al-2Cr-2Nb at 650 ℃.The fracture mode is a mixture of quasicleavage fracture and intergranular fracture,where cracks initiate near the cleaved γ grains and propagate along grain boundaries.Near the lamellar groups,the fracture mode is a mixture of trans-and interlamellar fractures.As the amplitude of the cyclic stress decreases,the failure mode transitions from fracture caused by long crack linkages following short crack propagation to fracture resulting from the interconnection of short cracks forming long cracks,leading to a reduction in fatigue life dispersion and a decrease in fracture surface roughness.