| Among all of currently available titanium alloys,the metastable ? titanium alloy has high specific strength,favorable cold and thermal workability and heat treatment strengthening effect,it is often applied to make key structural parts for aerospace vehicle,such as skin,structural main frame and special fastener,etc.It is the most suitable candidate for load-bearing structural parts aimed at weight reduction and acquisition of excellent mechanical properties.In this paper,the fatigue properties of a novel metastable ? titanium alloy Ti-6Mo-5V-3Al-2Fe(wt.%)were studied,and the low cycle fatigue tests of Ti-6Mo-5V-3Al-2Fe alloy in different states were carried out,i.e.hot rolled and aged states.The morphology of fractured surface was observed by scanning electron microscope.Low cycle fatigue behavior and fracture mechanism of Ti-6Mo-5V-3Al-2Fe alloy were studied,in order to provide a reliable theory basis for the practical application of this serial alloys.Experimental results show that the Ti-6Mo-5V-3Al-2Fe alloy under three states and low cycle fatigue loading controlled by total strain can exhibit cyclic stability and cyclic softening.Compared with the hot rolled alloy,the cyclic deformation resistance increases apparently after being aged at 500°C for 4 h;whereas when being aged 600°C,cyclic deformation resistance of the alloy decreases,but still higher than that of the hot rolled alloy.Low cycle fatigue life of Ti-6Mo-5V-3Al-2Fe alloy will reduce after aging treatment;for the low cycle fatigue life under T6 states,the value when being aged at 500°C is higher than that aged at600°C.The linear relationship between plastic strain amplitude,elastic strain amplitude and reverse cycle of loading at fracture is consistent with Coffin-Manson and Basquin formulas,respectively.In addition,the relationship between cyclic stress and plastic strain amplitudes can be described by an exponential law.Under the low cycle fatigue loading controlled by total strain,the fatigue cracks of Ti-6Mo-5V-3Al-2Fe alloy in three different states initiate on the surface of fatigue samples in trans-granular manner,and propagate in trans-granular manner as well. |
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