Room-Temperature High-Cycle Fatigue Fracture Features of TC4-DT Titanium Alloy
The damage tolerance type TC4-DT titanium alloy was subjected to room-temperature high-cycle fatigue tests under different stress ratios,and the macro-and micro-features of the typical fracture of smooth specimens and notched specimens with different fatigue lives were comparatively analyzed.The results show that the fatigue fracture of smooth specimens was generally rough,the cleavage characteristics were not obvious,but the fatigue bands were clear.The crack source of smooth specimens was mainly single source.The transient fracture zone of smooth specimens was almost crescent shaped and located on one side edge of the fracture.When the stress ratio was 0.5,there was no obvious flat fatigue crack extension zone of smooth specimens with 104 cycles of fatigue life,while the flat fatigue crack extension zone was observed on the fracture with the similar fatigue life under the stress ratio of-1.The fatigue cracks of smooth specimens were mainly initiated from the subsurface or inside under the stress ratio of 0.5,and were basically initiated from the surface under the stress ratio of-1.The fatigue fracture of notched specimens was generally flat,with cleavage-like characteristics and clear fatigue bands.The cracks of notched specimens were initiated from the notch root and had multiple sources.With the fatigue life extending from 104 cycles to 106 cycles,the transient fracture zone of notched specimens moved from the inside to the edge of the notch.The shape of the transient fracture zone of notched specimens was spindle-shaped under the stress ratio of-1,and changed from ellipse to spindle shape under the stress ratio of 0.5.The fatigue crack extension zone of notched specimens under stress ratio of 0.5 was smoother and flatter,and the characteristics of plastic fracture in the transient fracture zone was more obvious.
titanium alloyhigh-cycle fatigue fracture featuresmooth samplenotched samplestress ratio
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