高强韧Ti-3Al-5Mo-4Cr-2Zr-1Fe合金低周疲劳性能研究

通过室温下应变控制疲劳试验研究了高强韧Ti-3Al-5Mo-4Cr-2Zr-1Fe合金的低周疲劳性能.结果表明:在高应变幅值下(△εt/2=1.0％,1.2％,1.4％,1.6％),合金的循环应力响应表现为初始循环软化,而后趋于循环稳定;在低应变幅值下(△εt/2=0.6％,0.8％),合金的循环应力响应表现为循环饱和...

Study on Low Cycle Fatigue Behavior of Ti-3Al-5Mo-4Cr-2Zr-1Fe Alloy with High Strength and Toughness

Low cycle fatigue(LCF) behavior of Ti-3 Al-5 Mo-4 Cr-2 Zr-1 Fe(Ti-35421) alloy with bimodal microstructure consisting of lath α(αp) and βtrans was investigated by strain-controlled mode at room temperature. Results indicate that cyclic stress amplitudes of the Ti-35421 alloy with bimodal microstructure show cyclic softening at first, then reach to cyclic stability at high strain amplitude(Δεt/2=1.0%, 1.2%, 1.4%, 1.6%). However, the cyclic stress response characterizes cyclic saturation at low strain amplitudes(Δεt/2=0.6%, 0.8%). Only one fatigue crack source is found by fracture morphology observation when Δεt/2=0.6%, while a large number of small secondary cracks occur on the surface. On the contrary, multiple fatigue crack sources generate when the strain amplitude increases to 1.6%. The number of secondary cracks reduces, but the length and width of the secondary cracks increase significantly. TEM results indicate that a large number of dislocations generate at the αp/βtrans interface at the low strain amplitude(Δεt/2=0.6%), which leads to micro-crack nucleation due to the stress concentration. Meanwhile, at high strain amplitude(Δεt/2=1.6%), deformation inhomogeneity phenomena occur in the αp phase, a large number of dislocation tangles and dislocation debris form in the αp phase, and some dislocation pile-ups form in the αs phase instead of β matrix. Due to the elongated αp phase, it can improve the compatibility of alloy α phase and β phase deformation, and delay crack nucleation and propagation. Therefore, Ti-35421 alloy has excellent low cycle fatigue performance.